Data Conversion, Interface Signal Conditioning Products Richard Markel

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Data Conversion, Interface Signal Conditioning Products Richard Markel

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Linear Technology Magazine Circuit Collection, Volume
Data Conversion, Interface Signal Conditioning Products Richard Markell, Editor INTRODUCTION Application Note fifth series that excerpts useful circuits from Linear Technology magazine preserve them posterity. This application note highlights data conversion, interface signal conditioning circuits from issue VI:1 (February 1996) through issue VIII:4 (November 1998). Like predecessor, AN67, this Application Note includes circuits high speed video, interface swap circuits, active switched capacitor filter circuitry variety data conversion instrumentation circuits. There also several circuits that cannot neatly categorized. without further ado, I'll authors describe their circuits. Note: Article Titles appear this application note exactly they originally appeared Linear Technology magazine. This result some inconsistency usage terminology.
TABLE CONTENTS Introduction DATA CONVERTERS LTC1446 LTC1446L: World's First Dual 12-Bit DACs SO-8 Packages Multichannel Uses Single Antialiasing Filter. LTC1454/54L LTC1458/58L: Dual Quad 12-Bit, Rail-to-Rail, Micropower DACs Micropower SO-8 Give 12-Bit Analog Interface LTC1594 LTC1598: Micropower 8-Channel 12-Bit ADCs LTC1419 Without Software LTC1590 Dual 12-Bit Extremely Versatile. 16-Bit SO-8 1LSB Over Industrial Temperature LTC1659, LTC1448: Smallest Rail-to-Rail 12-Bit DACs Have Lowest Power SMBus-Controlled 10-Bit, Current Output, 50µA Full-Scale INTERFACE CIRCUITS Simple Resistive Surge Protection Interface Circuits LTC1343 LTC1344 Form Software-Selectable Multiple-Protocol Interface Port Using DB-25 Connector LT1328: Cost IrDA Receiver Solution Data Rates 4Mbps LTC1387 Single RS232/RS485 Multiprotocol Transceiver 10MB/s Multiple-Protocol Chip Supports Net1 Net2 Standards Net1 Net2 Serial Interface Chip Supports Test Mode. OPERATIONAL AMPLIFIERS/VIDEO AMPLIFIERS LT1490/LT1491 Over-the-TopDual Quad Micropower Rail-to-Rail Amps. LT1210: 1-Ampere, 35MHz Current Feedback Amplifier. LT1207: Elegant Dual 60MHz, 250mA Current Feedback Amplifier
AN87-1
Application Note
Micropower, Dual Quad JFET Amps Feature C-LoadCapability PicoAmpere Input Bias Currents. LT1210: High Power Yields Higher Voltage Current Rail-to-Rail Amplifiers: Precision Performance from Micropower High Speed LT1256 Voltage-Controlled Amplitude Limiter LT1495/LT1496: 1.5µA Rail-to-Rail Amps Send Camera Power Video Same Coax Cable 200µA, 1.2MHz Rail-to-Rail Amps Have Over-The-Top Inputs Distortion Rail-to-Rail Amps Have 0.003% with 100kHz Signal LT1167: Precision, Cost, Power Instrumentation Amplifier Requires Single Gain-Set Resistor Level Shift Allows Video Amplifier Swing Ground Single Supply LT1468: Operational Amplifier Fast, 16-Bit Systems TELECOMMUNICATIONS CIRCUITS Ring Phone with Quad Distortion, Power, Single-Pair HDSL Driver Using LT1497 COMPARATORS Ultralow Power Comparators Include Reference 4.5ns, 4mA, Single-Supply, Dual Comparator Optimized 3V/5V Operation INSTRUMENTATION CIRCUITS LTC1441-Based Micropower Voltage-to-Frequency Converter Bridge Measures Small Capacitance Presence Large Strays Water Tank Pressure Sensing, Fluid Solution 0.05µV/°C Chopped Amplifier Requires Only Supply Current 4.5ns Dual-Comparator-Based Crystal Oscillator Duty Cycle Complementary Outputs LTC1531 Isolated Comparator. FILTERS LTC1560-1: 1MHz/500kHz Continuous-Time, Noise, Elliptic Lowpass Filter LTC1067 LTC1067-50: Universal Order Noise, Rail-to-Rail Switched Capacitor Filters Universal Continuous-Time Filter Challenges Discrete Designs High Clock-to-Center Frequency Ratio LTC1068-200 Extends Capabilities Switched Capacitor Highpass Filter Clock-Tunable, High Accuracy, Quad Order, Analog Filter Building Blocks. MISCELLEANEOUS Biased Detector Yields High Sensitivity with Ultralow Power Consumption Zero-Bias Detector Yields High Sensitivity with Nanopower Consumption. Transparent Class-D Amplifiers Featuring LT1336 Single-Supply Random Code Generator APPENDIX COMPONENT VENDOR CONTACTS INDEX
LTC, registered trademarks Linear Technology Corporation; Adaptive Power, Burst Mode, C-Load, FilterCAD, RSENSE, Operational Filter, Over-The-Top, PolyPhase, PowerPath UltraFast trademarks Linear Technology Corporation. Gelcell trademark Johnson Controls, Inc.; Kool registered trademark Magnetics, Inc.; Pentium registered trademark Intel Corp.; VERSA-PAC trademark Coiltronics, Inc.
AN87-2
Application Note
Data Converters LTC1446 LTC1446L: WORLD'S FIRST DUAL 12-BIT DACS SO-8 PACKAGES Hassan Malik Brubaker Dual 12-Bit Rail-to-Rail Performance Tiny SO-8 LTC1446 LTC1446L dual 12-bit, single-supply, rail-to-rail voltage output digital-to-analog converters. Both these parts include internal reference DACs with rail-to-rail output buffer amplifiers, packed small, space-saving 8-pin PDIP package. power-on reset initializes outputs zero-scale power-up. LTC1446 output swing 4.095V, making each equal 1mV. operates from single 4.5V 5.5V supply, dissipating 3.5mW (ICC typical 700µA).
22µF
LTC1446L output swing 2.5V. operate single supply with wide range 2.7V 5.5V. dissipates 1.35mW (ICC typical 450µA) supply.
Autoranging 8-Channel with Shutdown
Figure shows LTC1446 make autoranging ADC. microprocessor sets reference span common analog input loading appropriate digital code into LTC1446. VOUTA controls common analog inputs LTC1296 VOUTB controls reference span setting REF+ LTC1296. LTC1296 shutdown that goes shutdown mode. This will turn transistor supplying power LTC1446. resistor capacitor LTC1446 outputs lowpass filter noise.
DOUT LTC1296 CS/LD LTC1446 DOUT
ANALOG INPUT CHANNELS
74HC04 0.1µF 2N3906 VOUTB
0.1µF
VOUTA 0.1µF
Figure Autoranging 8-Channel with Shutdown
AN87-3
Application Note
Wide-Swing, Bipolar-Output with Digitally Controlled Offset
Figure shows LTC1446 LT1077 make wide bipolar-output-swing 12-bit with offset that digitally programmed. VOUTA, which
8.192 0.1µF VOUTB 4.99k CS/LD LTC1446 VOUT 4.096 VOUTA 2.048V (MID SCALE) LT1077 VOUT VOUTB-VOUTA VOUTA 4.096V (FULL SCALE) -4.096 -15V 49.9k NEXT 100k -8.192 VOUTA (ZERO SCALE)
loading appropriate digital code sets offset. this value changes, transfer curve output moves down, shown figure.
DOUT
VOUTA
Figure Wide-Swing, Bipolar Output with Digitally Controlled Offset
MULTICHANNEL USES SINGLE ANTIALIASING FILTER Applications Staff circuit Figure demonstrates LTC1594's independent analog multiplexer simplify design 12-bit data acquisition system. four channels MUXed into single 1kHz, fourth-order Sallen-Key antialiasing filter, which designed single-supply operation. Since LTC1594's data converter accepts inputs from ground positive supply, rail-to-rail amps were chosen filter maximize dynamic range. LT1368 dual rail-to-rail compensated 0.1µF load capacitors that help reduce amplifier's output impedance improve supply rejection high frequencies. filter contributes less than 1LSB error offsets bias currents. filter's noise distortion less than -72dB 100Hz, 2VP-P offset sine input. combined errors result integral nonlinearity error ±3LSB (maximum) differential nonlinearity error ±0.75LSB (maximum). typical signal-to-noise plus distortion ratio 68dB, with approximately -78dB total harmonic distortion. LTC1594 programmed through 4-wire serial interface that allows efficient data transfer wide variety microprocessors microcontrollers. Maximum serial clock speed 200kHz, which corresponds 10.5kHz sampling rate. complete circuit consumes approximately 800µA from single supply. ratiometric measurements, A/D's reference also taken from supply. Otherwise, external reference should used.
AN87-4
Application Note
0.015µF 0.1µF
LT1368
7.5k
7.5k 0.03µF 0.1µF
ANALOG INPUTS LTC1594 VREF 0.1µF 7.5k 7.5k DOUT DATA CLOCK DATA CHIP SELECT 0.015µF
LT1368
0.03µF
0.1µF
Figure Simple Data Acquisition System Takes Advantage LTC1594's OUT/SHA Loop Filter Analog Signals Prior Conversion
LTC1454/54L LTC1458/58L: DUAL QUAD 12-BIT, RAIL-TO-RAIL, MICROPOWER DACS Hassan Malik Brubaker Dual Quad Rail-to-Rail DACs Offer Flexibility Performance LTC1454 LTC1454L dual 12-bit, single supply, rail-to-rail voltage-output digital-to-analog converters. LTC1458 LTC1458L quad versions this family. These DACs have easy-to-use, SPI-compatible interface. power-on-reset both reset outputs zero scale. guaranteed less than 0.5LSB. Each rail-to-rail voltage output buffer amplifier. onboard reference brought separate connected REFHI pins DACs. There also REFLO that used offset range. further flexibility each allows user select gain either LTC1454/54L available 16-pin PDIP packages, LTC1458/58L available 28-pin SSOP packages.
Single Supply Micropower LTC1454 LTC1458 operate from single 4.5V 5.5V supply. LTC1454 dissipates 3.5mW (ICC typical 700µA), whereas LTC1458 dissipates 6.5mW (ICC typical 1.3mA). There onboard reference 2.048V nominal full scale 4.095V when using onboard reference gain-of-2 configuration. LTC1454L LTC1458L operate single supply with wide range 2.7V 5.5V. LTC1454L dissipates 1.35mW (ICC typical 450µA), whereas LTC1458L dissipates 2.4mW (ICC typical 800µA) from supply. There 1.22V onboard reference convenient full scale 2.5V when using onboard reference gain-of-2 configuration. Flexibility Allows Host Applications These products used wide range applications, including digital calibration, industrial process control, automatic test equipment, cellular telephones portable, battery-powered systems.
AN87-5
Application Note
12-Bit with Digitally Programmable Full Scale Offset
Figure shows LTC1458 make 12-bit with digitally programmable full scale offset. used control offset full scale connected configuration controls offset moving REFLOC above ground. minimum value which this offset programmed 10mV. connected configuration controls full scale DAC-C driving REFHIC Note that voltage REFHIC must less than equal VCC/2, corresponding code 2,500 since DAC-C being operated mode full rail-to-rail output swing. transfer characteristic VOUTC REFOUT where REFOUT reference output (DAC digital code)/4096 this sets offset (DAC digital code)/4096 this sets full scale (DAC digital code)/4096
Single-Supply, 4-Quadrant Multiplying
LTC1454L also used four-quadrant multiplying with offset signal ground 1.22V. This application shown Figure inputs connected REFHIB REFHIA have 1.22V amplitude around signal ground 1.22V. outputs will swing from 2.44V, shown equation with figure.
LTC1458L/LTC1458 X1/X2C VOUT VOUTC CS/LD REFHIC REFLOC REFLOD REFHI DOUT VOUTD X1/X2D X1/X2B VOUTB REFHIB REFLOB REFLOA REFHIA REFOUT VOUTA X1/X2A
0.1µF 0.1µF X1/X2 CS/LD VOUT REFHI 1.22V 1.22V VOUT
LTC1454L REFLO CS/LD DOUT X1/X2 REFHI 1.22V 1.22V 1.22V
VOUT
VOUT
(VIN VREF)
GAIN
1.22
4096
2.05 -1.05 1.22V 4096
1454_4.eps
Figure 12-Bit with Digitally Controlled Zero Scale Full Scale
Figure Single-Supply, 4-Quadrant Multiplying
AN87-6
Application Note
MICROPOWER SO-8 GIVE 12-BIT ANALOG INTERFACE Applications Staff Needing channels simple, inexpensive, powered, compact analog input/output computer, LTC1298 LTC1446 were chosen. LTC1298 LTC1446 first SO-8 packaged 2channel devices their kind. LTC1298 draws just 340µA. built-in auto shutdown feature further reduces power dissipation reduced sampling rates 30µA 1ksps). Operating supply, LTC1446 draws just (typ). Although application shown data acquisition, these converters provide smallest, lowest power solutions many other analog applications. circuit shown Figure connects PC's serial interface using four interface lines: DTR, RTS, used transmit serial clock signal, used transfer data ADC, used receive conversion results from LTC1298 signal selects either LTC1446 LTC1298 receive input data. LTC1298's LTC1446's power dissipation allows circuit powered from serial port. lines charge capacitor through diodes LT1021-5 regulates voltage Returning lines logic high after sending data completion conversion provides constant power LT1021-5. Using 486-33 throughput 3.3ksps LTC1298 2.2ksps LTC1446. Your mileage vary. Listing code that prompts user either read conversion result from ADC's write data word both channels.
1N914 INPUT INPUT LTC1298 DOUT 1N914 LTC1446 AOUT1 AOUT2 CS/LD DOUT VOUTB VOUTA 0.1µF 74HC74 0.1µF SELECT SCLK DOUT 1N914
DI1466_01.eps
LT1021-5 150µF
74HC74 0.1µF
47µF
Figure Communicating Over Serial Port, LTC1298 LTC1446 SO-8 Create Simple, Power, 2-Channel Analog Interface Listing Code Configure Analog Interface #define #define #define #define #define #define #define port 0x3FC inprt 0x3FE 0x3FB high Clock 0x01 0x02 Control register, RS232 Status reg. RS232 Line Control Register
AN87-7
Application Note
#define Dout 0x10 input #include<stdio.h> #include<dos.h> #include<conio.h> Function module sets high void set_control(int Port,char bitnum,int flag) char temp; temp inportb(Port); (flag==high) temp bitnum; output high else temp ~bitnum; output outportb(Port,temp); This function brings high (consult schematic) void CS_Control(direction) (direction) set_control(port,Clock,low); clock high read set_control(port,Din,low); set_control(port,Din,low); high make goes high else outportb(port, 0x01); clock Delay(10); outportb(port, 0x03); goes high make This function outputs 24-bit (2x12) digital code LTC1446L void Din_(long code,int clock) for(x x<clock; ++x) code align (code 0x1000000) set_control(port,Clock,high); Clock set_control(port,Din,high); high else set_control(port,Clock,high); Clock set_control(port,Din,low); set_control(port,Clock,low); Clock high latch
AN87-8
Application Note
Read from Dout_() temp, volt for(x x<13; ++x) set_control(port,Clock,high); set_control(port,Clock,low); temp inportb(inprt); read status reg. volt shift left serial transmission if(temp Dout) volt input high return(volt 0xfff); menu mode selection char menu() printf("Please select following:\na: ADC\nd: DAC\nq: quit\n\n"); return (getchar()); void main() long code; char mode_select; temp,volt=0; Chip select controlled RS232 line. When LCR's set, selected reverse true ADC. outportb(LCR,0x0); initialize outportb(LCR,0x64); initialize while((mode_select menu()) `q') switch(mode_select) case `a': outportb(LCR,0x0); selecting CS_Control(low); enabling Din_(0x680000, 0x5); channel selection volt Dout_(); outportb(LCR,0x64); bring high set_control(port,Din,high); bring signal high printf("\ncode: %d\n",volt); break; case `d':
AN87-9
Application Note
printf("Enter input code 4095):\n"); scanf("%d", &temp); code temp; code (long)temp converting 12-bit 24-bit word outportb(LCR,0x64); selecting CS_Control(low); enable Din_(code,24); loading digital data outportb(LCR,0x0); bring high outportb(LCR,0x64); disabling set_control(port,Din,high); bring signal high break;
LTC1594 LTC1598: MICROPOWER 8-CHANNEL 12-BIT ADCS Marco Micropower ADCs Small Packages LTC1594 LTC1598 micropower 12-bit ADCs that feature 8-channel multiplexer, respectively. LTC1594 available 16-pin package LTC1598 available 24-pin SSOP package. Each
includes simple, efficient serial interface that reduces interconnects and, thereby, possible sources corrupting digital noise. Reduced interconnections also reduce board size allow processors having fewer pins, both which help reduce system costs. LTC1594 LTC1598 include auto shutdown feature that reduces power dissipation when converter inactive (whenever signal logic high).
ANALOG INPUTS RANGE
DATA DATA CHIP SELECT CLOCK
1598_02.eps
0.015µF
LT1368 7.5k 7.5k 0.015µF 0.1µF
7.5k
7.5k 0.03µF
LTC1598 DOUT MUXOUT ADCIN VREF
LT1368
0.03µF
0.1µF
Figure Simple Data Acquisition System Takes Advantage LTC1598's OUT/ADCIN Pins Filter Analog Signals Prior Conversion
AN87-10
Application Note
LTC1391 LTC1598 MUXOUT 8-CHANNEL 12-BIT SAMPLING µP/µC
LT1368 0.1µF ADCIN VREF
DOUT
DOUT
1598_03.eps
Figure Using MUXOUT/ADCIN Loop LTC1598 Form with Eight Gains Noninverting Configuration
MUXOUT/ADCIN Loop Economizes Signal Conditioning MUXOUT ADCIN pins form very flexible external loop that allows and/or processing analog input signals prior conversion. This loop also cost effective perform conditioning, because only circuit needed instead each channel. Figure shows loop being used antialias filter several analog inputs. output signal selected channel, present MUXOUT pin, applied Sallen-Key filter. filter bandlimits analog
Table Gain Each Channel Figures
Channel Noninverting Gain Inverting Gain -128
signal output applied ADCIN. LT1368 railto-rail amps used filter will, when lightly loaded this application, swing within positive supply voltage. Since only circuit used channels, each channel sees same filter characteristics. Using MUXOUT/ADCIN Loop Combined with LTC1391 shown Figure LTC1598's MUXOUT/ADCIN loop LT1368 used create 8-channel with eight noninverting gains each channel. output LT1368 drives ADCIN resistor ladder. resistors above selected channel form feedback LT1368. loop gain this amplifier (RS1/RS2) summation resistors above selected channel summation resistors below selected channel. selected, loop gain since Table shows gain each channel. LT1368 dual rail-to-rail designed operate with 0.1µF load capacitors. These capacitors provide frequency compensation amplifiers, help reduce amplifiers' output impedance improve
AN87-11
Application Note
supply rejection high frequencies. Because LT1368's low, selected channel will affect loop gain given formula above. case inverting configuration Figure selected channel's will added resistor that sets loop gain. 8-Channel, Differential, 12-Bit System Using LTC1391 LTC1598 LTC1598 combined with LTC1391 8channel, serial-interface analog multiplexer create differential system. Figure shows complete 8channel, differential circuit. system uses LTC1598's noninverting input multiplexer LTC1391 inverting input multiplexer. LTC1598's MUXOUT drives ADCIN directly. inverting multiplexer's output applied LTC1598's input. LTC1598 LTC1391 share DIN, control signals. This arrangement simultaneously selects same channel each multiplexer maximizes system's throughput. dotted-line connection daisy-chains MUXes LTC1391 LTC1598 together. This configuration provides flexibility select channel noninverting input with respect channel inverting input MUX. This allows combination signals applied inverting noninverting inputs routed conversion.
LTC1391
128R 12-BIT SAMPLING
LT1368
0.1µF
128R
LTC1598 MUXOUT
ADCIN
VREF
DOUT
1598_04.eps
Figure Using MUXOUT/ADCIN Loop LTC1598 Form with Eight Inverting Gains
LTC1598 MUXOUT 8-CHANNEL 12-BIT SAMPLING ADCIN VREF
DOUT
1598_05.eps
DOUT
DOUT
Figure Using LTC1598 LTC1391 8-Channel, Differential 12-Bit System: Opening Indicated Connection Shorting Dashed Connection Daisy-Chains External Internal MUXes, Increasing Channel-Selection Flexibility.
AN87-12
Application Note
LTC1419 WITHOUT SOFTWARE Applications Staff circuit shown Figure uses hardware instead software routines select multiplexer channels data acquisition system. circuit features LTC1419 800ksps 14-bit ADC. receives converts signals from 74HC4051 8-channel multiplexer. Three four output bits from additional circuit, 74HC4520 dual 4bit binary counter, used select multiplexer channel. logic high power-on processor-generated reset applied counter's After counter cleared, multiplexer's channel selection input input channel applied LTC1419's input. channel-selection counter clocked rising edge convert start (CONVST) signal that initiates conversion. each CONVST pulse increments counter from 111, each multiplexer channel individually selected input signal applied LTC1419. After each eight channels been selected, counter rolls over zero
74HC4051 0.1µF LTC1419 74HC4520 0.1µF DATA 0-13 CLEAR COUNT 1CLK 1CLEAR 2CLEAR 2CLK
process repeats. time, input multiplexer channel reset applying logic-high pulse counter. This data acquisition circuit throughput 800ksps 100ksps/channel. shown Figure SINAD 76.6dB full-scale ±2.5V, 1.19kHz sine wave input signal.
AMPLITUDE (dB) -100 -120 -140 fSAMPLE 100ksps 1.19kHz ±2.5V
INPUT FREQUENCY (kHz)
Figure MUXed LTC1419's Conversion Full-Scale 1.19kHz Sine Wave
10µF 10µF
DI_MUX_02.EPS
0.1µF
0.1µF BUSY
0.1µF
AVDD DVDD BUSY CONVST SHDN
VREF COMP AGND (MSB) DGND
10µF
0.1µF
CONVERT CONTROL
DI_MUX_01.EPS
Figure This Simple Stand-Alone Circuit Requires Software Sequentially Sample Convert Eight Analog Signal Channels 14-bit Resolution 100ksps/Channel.
AN87-13
Application Note
LTC1590 DUAL 12-BIT EXTREMELY VERSATILE Applications Staff CMOS multiplying DACs make versatile building blocks that beyond their basic function converting digital data into analog signals. This article details some other circuits that possible when using LTC1590 dual, serially interfaced 12-bit DAC. circuit shown Figure uses LTC1590 create digitally controlled attenuator using DACA programmable gain amplifier (PGA) using DACB. attenuator's gain using following equation:
VOUT -VIN
PGA's gain using following equation:
VOUT -VIN
where VOUT
output voltage input voltage resolution bits value code applied (min code 001H)
gain adjustable from 4096/4095 4096/1. code meaningless, since this results infinite gain amplifier operates open loop. With either configuration, attenuator's PGA's gain with bits accuracy. further modification basic attenuator shown Figure this circuit, DACA's attenuator circuit modified give output amplifier gain ratio resistors equation this attenuator with output gain
VOUT -VIN
where VOUT
output voltage input voltage resolution bits value code applied (min code 000H)
attenuator's gain varies from 4095/4096 1/4096. code used completely attenuate input signal.
0.1µF ±10V
PROGRAMMABLE ATTENUATOR 33pF
LTC1590
0.01µF
24-BIT SHIFT REGISTER LATCH
DATA SERIAL CLOCK CHIP SELECT/ LOAD DATA CLEAR
CS/LD DOUT
DACA OUT2A
OUT2B DACB OUT1B VREF 33pF
LT1358 0.01µF
AGND DGND
±10V
PROGRAMMABLE GAIN AMPLIFIER
Figure Driving DACA's Reference Input (VREF) Tying Feedback Resistor (RFB) Amp's Output Creates 12-Bit- Accurate Attenuator. Reversing VREF Connections Configures DACB Programmable-Gain Amplifier.
AN87-14
VREF
OUT1A
VOUT VOUT -VIN
LT1358
VOUT -VIN VOUT
DI1590_01.EPS
-15V
Application Note
0.1µF ±10V OUT1A 33pF
0.01µF
24-BIT SHIFT REGISTER LATCH
DATA SERIAL CLOCK CHIP SELECT/ LOAD DATA CLEAR
CS/LD DOUT
DACA OUT2A
LTC1590 OUT2B DACB OUT1B VREF 33pF
DI1590_02.EPS
LT1358
AGND DGND
±10V
Figure Modifying Basic Attenuator Creates Gain Attenuator Attenuation PGA's Input R2).
With values shown, attenuator's gain range -1/256 -16. This range easily modified changing ratio other half circuit, attenuator been added input DACB, configured PGA. equation this with input attenuation
VOUT -VIN
cutoff frequency range function DAC's resolution digital data that sets effective resistance. effective resistance
RREF
Using this effective resistance, cutoff frequency
2n+1
This sets gain range from effectively -1/16 -256. Again, this range modified changing ratio LTC1590 also used control element that sets lowpass filter's cutoff frequency. This shown Figure becomes adjustable resistor that sets time constant integrator formed With integrator enclosed within feedback loop, lowpass filter created.
cutoff frequency range varies from 0.0000389/RC 0.159/RC. example, minimum cutoff frequency 10Hz, make 8.25k 470pF. input code cutoff frequency 10Hz. cutoff frequency increases linearly with increasing code, becoming 40.95kHz code 4095. Generally, code changes bit, cutoff frequency changes amount equal frequency this example, cutoff frequency changes 10Hz steps.
VREF
VOUT
LT1358
VOUT -VIN
VOUT -VIN VOUT
0.01µF
-15V
AN87-15
Application Note
0.01µF
24-BIT SHIFT REGISTER LATCH
DACA OUT2A
LT1358
DATA SERIAL CLOCK CHIP SELECT/ LOAD DATA CLEAR
CS/LD DOUT
LTC1590 OUT2B DACB OUT1B VREF
LT1358 0.01µF
AGND DGND
LT1358 -15V -15V
0.01µF
-15V
DI1590_03.EPS
Figure This LTC1590-Controlled Dual Single-Pole Lowpass Filter Uses DAC's Input Code Create Effective Resistance that Sets Integrator's Time Constant and, Therefore, Circuit's Cutoff Frequency.
16-BIT SO-8 1LSB OVER INDUSTRIAL TEMPERATURE Brubaker William Rempfer generations industrial systems moving bits hence require high performance 16-bit data converters. LTC1595/LTC1596 16-bit DACs provide easiest use, most cost effective, highest performance solution industrial instrumentation applications. LTC1595/LTC1596 serial input, 16-bit, multiplying current output DACs. Features DACs include:
±1LSB maximum over industrial temperature range Ultralow, 1nV-s glitch impulse ±10V output capability Small SO-8 package (LTC1595) Pin-compatible upgrade industry-standard 12-bit DACs (DAC8043/8143 AD7543)
AN87-16
0.1µF
0.01µF 0.01µF VREF OUT1A
LT1358
VOUT
LT1358
2n+1
LT1358 0.01µF
VOUT
Application Note
0V-10V ±10V Output Capability Precision 0V-10V Outputs with Figure shows circuit 0V-10V output range. uses external reference single this configuration. This circuit also perform 2quadrant multiplication where reference input driven ±10V input signal VOUT swings from -VREF. full-scale accuracy circuit very precise because determined precision-trimmed internal resistors. power dissipation circuit dissipation current drawn from reference input nominal). supply current itself less than 10µA. advantage LTC1595/LTC1596 ability choose output optimize accuracy, speed, power cost application. Using LT1001 provides excellent precision, noise power dissipation (90mW total Figure 16's circuit). higher speed, LT1007, LT1468 LT1122 used. LT1122 will provide settling 1LSB full-scale transition. Figure shows settling performance obtained with LT1122. feedback capacitor Figure ensures stability. higher speed applications, used optimize transient response. slower applications, capacitor increased reduce glitch energy provide filtering.
CLOCK DATA LOAD VREF (-10V 10V) VREF LTC1595 OUT1 33pF
Figure With Single External Amp, Performs 2-Quadrant Multiplication with ±10V Input -VREF Output. With Fixed -10V Reference, Provides Precision 0V-10V Unipolar Output.
VOUT 5V/DIV
GATED VOUT 500µV/DIV
1µs/DIV
Figure When Used with LT1122 Circuit Figure 16), LTC1595/LTC1596 Settle Full-Scale Step. Trace Shows Output Swinging from 10V. Bottom Trace Shows Gated Settling Waveform Settling 1LSB (1/3 Division) 3µs.
VREF (-10V 10V) 0.1µF VREF
OUT1
33pF
LTC1595
LT1112
Figure With Dual Amp, Performs 4-Quadrant Multiplication. With Fixed Reference, Provides ±10V Bipolar Output.
LT1112
VOUT (-VREF VREF)
1595_05.EPS
LT1001
VOUT -VREF
1595_04.EPS
AN87-17
Application Note
Precision ±10V Outputs with Dual Figure shows bipolar, 4-quadrant multiplying application. reference input vary from -10V VOUT swings from -VREF +VREF. fixed reference used, precision ±10V bipolar output will result. Unlike unipolar circuit Figure bipolar gain offset will depend matching external resistors. good provide good matching save board space pack matched resistors (the unit formed placing resistors parallel). LT1112 dual excellent choice high precision, power applications that require high speed. LT1469 LT1124 will provide faster settling. Again, with selection user optimize speed, power, accuracy cost application.
LTC1659, LTC1448: SMALLEST RAIL-TO-RAIL 12-BIT DACS HAVE LOWEST POWER Hassan Malik this portable electronics, power size primary concerns most designers. LTC1659 LTC1448 rail-to-rail, 12-bit, voltage output DACs that address both these concerns. LTC1659 single MSOP-8 package that draws only 250µA from supply, whereas LTC1448 dual SO-8 package that draws 450µA from supply. Figure shows convenient LTC1659 digital control loop where 12-bit resolution required. output LTC1659 will swing from VREF, because there gain from VOUT full-scale. Because output only swing VCC, VREF should less than equal prevent loss codes degradation PSRR near full-scale. obtain full dynamic range, connected supply pin, which driven from reference guarantee absolute accuracy (see Figure 20). LT1236 precision reference with input range 7.2V 40V. this configuration, LTC1659 wide output swing LTC1448 used similar configuration where dual DACs needed.
2.7V 5.5V
VREF
VOUT CONTROL VOLTAGE VREF)
LTC1659
CS/LD
Figure 12-Bit Digital Control Loop
1659_01
LT1236 (7.2V 40V) 0.1µF
CS/LD
LTC1659
VOUT CONTROL VOLTAGE
1659_02
Figure 12-Bit with Wide Output Swing
AN87-18
Application Note
SMBus-CONTROLLED 10-BIT, CURRENT OUTPUT, 50µA FULL-SCALE Ricky Chow LTC1427-50 10-bit, current-output with SMBus interface. This device provides precision, fullscale current 50µA ±1.5% room temperature (±2.5% over temperature), wide output voltage compliance (from -15V (VCC 1.3V)) guaranteed monotonicity over wide supply-voltage range. ideal part applications contrast/brightness control voltage adjustment feedback loops. Digitally Controlled Bias Generator Figure schematic digitally controlled bias generator using standard SMBus 2-wire interface. LT1317 configured boost converter, with output voltage (VOUT) determined values feedback resistors, LTC1427-50's current output connected feedback node LT1317. LTC1427-50's current output increases decreases according data sent SMBus. output current varies from 50µA, output voltage controlled over range 12.7V 24V. 1LSB change output current corresponds 11mV change output voltage.
CELLS SHDN LT1317 SHDN
VOUT* 226k 12.1k 4700pF 100k 3.3V
LTC1427-50 SHDN IOUT P1.2 P1.1 P1.0 *VOUT 12.7V-24V 11mV STEPS 15mA FROM CELLS 35mA FROM CELLS
(e.g., 8051)
10µH (SUMIDA CD43 MURATA-ERIE LQH3C COILCRAFT DO1608) SEMICONDUCTOR MBR0530
Figure Digitally Controlled Bias Generator
AN87-19
Application Note
Interface Circuits SIMPLE RESISTIVE SURGE PROTECTION INTERFACE CIRCUITS Applications Staff Surges Circuits Many interface circuits must survive surge voltages such those created lightning strikes. These high voltages cause devices within break down conduct large currents, causing irreversible damage Engineers must design circuits that tolerate surges expected their environments. They quantify surge tolerance circuitry using surge standard. Standards differ mainly their voltage levels wave forms. LTC, test surge resistance using circuit Figure describe voltage wave form (Figure peak value "front time" (roughly, rise time), "time half-value" T1/2 (roughly, time from beginning pulse when pulse decays half VP). Surges similar ESD, challenge circuits different way. surge rise 10ms, whereas pulse might rise 15kV only However, surge lasts more than 100ms, whereas pulse decays about 50ns. Thus, surge challenges power dissipation ability protection circuitry, whereas challenges turn-on time peak current handling. Linear Technology LT1137A on-chip circuitry withstand pulses 15kV (IEC 801-2). This circuitry also increases surge tolerance LT1137A relative standard 1488/1489.
10µs T1/2 120µs VOLTAGE VP/2
T1/2 TIME CONTROLLED COUT T1/2 CONTROLLED SUPPLY
Figure Surge-Test Waveform
Designing Surge Tolerance Many designers enhance surge tolerance circuit placing transient voltage suppressor (TVS) parallel with vulnerable pins, shown Figure contains Zener diodes, which break down certain voltage shunt surge current ground. Thus, clamps voltage level safe TVS, like protection circuitry, increases manufacturing cost complexity circuit. Alternately, designers series resistor protect vulnerable pins, shown Figure resistor reduces current
0.1µF 1488 VCC+ 0.1µF
SUPPLY
COUT 0.05µF
CONTROLLED COUT T1/2 CONTROLLED SUPPLY
Figure Surge-Test Circuit: Controlled COUT; T1/2 Controlled Supply
Figure 1488 Line Driver with Surge Protection
AN87-20
Application Note
0.1µF 0.1µF LT1137A LINE 0.1µF LOGIC 0.1µF 0.1µF
2V/DIV
130kBd
5µs/DIV
2V/DIV
130kBd
5µs/DIV
ON/OFF
Figure Output Waveforms with Series Resistor
LT1137A SCOPE 0.1µF 0.1µF 0.1µF
Figure LT1137A with Resistive Surge Protection
flowing into safe level. Resistive protection simplifies design inventory offer lower cost. resistance must large enough protect large that degrades frequency performance circuit. Larger surge amplitudes require increased resistance protect More robust need less
1200 1000 SAFE SURGE SERIES LT1137A SAFE CURVE 1488 SAFE CURVE
0.1µF
130k baud
2.5nF
ON/OFF
Figure Safe Curves 1488 (SN75188N) LT1137A. Safe Curves Represent Highest Which Damage Occurred After Surges
Figure Testing Line Driver Output Waveform
AN87-21
Application Note
resistance protection against given surge amplitude. Linear's LT1137A protected much smaller resistor than 1488, shown Figure These curves empirical "rules thumb." should test actual circuits. series resistor have adverse effect frequency performance circuit. When protecting receiver, resistor little effect. Figures show effect resistor driver-output wave form. These waveforms were obtained with test circuit Figure resistor adequate surges, minimal effect driver wave form 130kbaud, even with worst-case load 3k||2.5nF. must choose series resistor carefully withstand surge. Unfortunately, neither voltage ratings power ratings provide adequate basis choosing surgetolerant resistors. Usually, through-hole resistors will withstand much larger surges than surface mount resistors same value power rating. Typical Watt surface mount resistors suitable protecting LT1137A. surface mount components, need ratings more. With LT1137A, carbon film 1/4W through-hole resistors against surges about 900V, 1/2W carbon film resistors against surges about 1200V. Unfortunately, using series parallel combinations resistors does increase surge handling would expect. Resistive Surge Protection LT1137A proprietary circuitry that makes more robust against surges than standard 1488/ 1489. greater surge tolerance LT1137A makes practical resistive surge protection, reducing inventory component cost relative surge protection. major considerations surge tolerance required, resulting resistor value needed, resistor robustness frequency performance.
LTC1343 LTC1344 FORM SOFTWARESELECTABLE MULTIPLE-PROTOCOL INTERFACE PORT USING DB-25 CONNECTOR Robert Reay Introduction With explosive growth data networking equipment come need support many different serial protocols using only connector. problem facing interface designers make circuitry each serial protocol share same connector pins without introducing conflicts. main source frustration that each serial protocol requires different line termination that easily cheaply switched. With introduction LTC1343 LTC1344, complete software-selectable serial interface port using inexpensive DB-25 connector becomes possible. chips form serial interface port that supports V.28 (RS232), V.35, V.36, RS449, EIA-530, EIA-530A X.21 protocols either mode both NET1 NET2 compliant. port runs from single supply
supports echoed clock loop-back configuration that helps eliminate glue logic between serial controller line transceivers. typical application shown Figure LTC1343s LTC1344 form interface port using DB-25 connector, shown here mode. Each LTC1343 contains four drivers four receivers LTC1344 contains switchable resistive terminators. first LTC1343 connected clock data signal lines along with diagnostic (local loopback) (test mode) signals. second LTC1343 connected control-signal lines along with diagnostic (remote loop-back) signal. single-ended driver receiver could separated support (ring-indicate) signal. switchable line terminators LTC1344 connected only high speed clock data signals. When interface protocol changed digital mode selection pins (not shown), drivers receivers automatically reconfigured appropriate line terminators connected.
AN87-22
Application Note
SCTE
LTC1343
LTC1343
LTC1344
(107)
(140)
Review Interface Standards serial interface standards RS232, EIA-530, EIA-530A, RS449, V.35, V.36 X.21 specify function each signal line, electrical characteristics each signal, connector type, transmission rate data exchange protocols. RS422 (V.11) RS423 (V.10) standards merely define electrical characteristics. RS232 (V.28) V.35 standards also specify their electrical characteristics. general, standards start with EIA, equivalent European standards start with characteristics each interface summarized Table Table shows only most commonly used signal lines. Note that each signal line must conform only four electrical standards, V.10, V.11, V.28 V.35.
V.10 (RS423) Interface
typical V.10 unbalanced interface shown Figure V.10 single-ended generator (output with ground
(106)
(108)
(105)
SHIELD (101)
SGND (102)
(142)
(104)
(115)
(109)
SCTE
SCTE (113)
(103)
(141)
(114)
DB-25 CONNECTOR
Figure LTC1343/LTC1344 Typical Application
BALANCED INTERCONNECTING CABLE
GENERATOR
LOAD CABLE TERMINATION RECEIVER
Figure Typical V.10 Interface
51.5 51.5 LTC1344 RECEIVER LTC1343
Figure V.10 Receiver Configuration
AN87-23
Application Note
Table Interface Summary
Clock Data Signals CCITT# RS232 EIA-530 EIA-530A RS449 V.35 V.36 X.21 (103) V.28 V.11 V.11 V.11 V.35 V.11 V.11 SCTE (113) V.28 V.11 V.11 V.11 V.35 V.11 V.11 (114) V.28 V.11 V.11 V.11 V.35 V.11 V.11 (115) V.28 V.11 V.11 V.11 V.35 V.11 V.11 (104) V.28 V.11 V.11 V.11 V.35 V.11 V.11 (105) V.28 V.11 V.11 V.11 V.28 V.11 V.11 (108) V.28 V.11 V.10 V.11
Control Signals (107) V.28 V.11 V.10 V.11 V.28 V.11
Test Signals (106) V.28 V.11 V.11 V.11 V.28 V.11
(125) V.28
(141) V.28 V.10 V.10 V.10
(140) V.28 V.10 V.10 V.10
(142) V.28 V.10 V.10 V.10
(109) V.28 V.11 V.11 V.11 V.28 V.11 V.11
V.10 V.10
V.10
V.10
V.10
connected differential receiver with input connected input connected signal-return ground receiver's ground separate from signal return. Usually, cable termination between required V.10 interfaces. V.10 receiver configuration LTC1343 LTC1344 shown Figure V.10 mode, switches inside LTC1344 inside LTC1343 turned off. Switch inside LTC1343 shorts noninverting receiver input ground input connector left floating. cable termination then input impedance ground LTC1343 V.10 receiver.
receiver with minimum value 100. termination resistor optional V.11 specification, high speed clock data lines, termination required prevent reflections from corrupting data. V.11 mode, switches except inside LTC1344, which connects differential termination impedance cable, shown Figure
V.28 (RS232) Interface
typical V.28 unbalanced interface shown Figure V.28 single-ended generator (output with ground connected single-ended receiver with input connected ground connected signal return ground V.28 mode, switches except inside LTC1343, which connects impedance (R8) ground parallel with (R5) plus (R6), combined impedance shown Figure noninverting input disconnected inside LTC1343 receiver connected level reference voltage 1.4V receiver trip point.
51.5 LTC1344 51.5 RECEIVER LTC1343
V.11 (RS422) Interface
typical V.11 balanced interface shown Figure V.11 differential generator with outputs ground connected differential receiver with ground input connected input connected V.11 interface differential termination
GENERATOR BALANCED INTERCONNECTING CABLE LOAD CABLE TERMINATION RECEIVER
Figure Typical V.11 Interface
Figure V.11 Receiver Configuration
AN87-24
Application Note
GENERATOR BALANCED INTERCONNECTING CABLE LOAD LOAD CABLE TERMINATION RECEIVER GENERATOR BALANCED INTERCONNECTING CABLE CABLE TERMINATION RECEIVER
Figure Typical V.28 Interface
51.5 51.5 LTC1344 RECEIVER 51.5 LTC1343 51.5
Figure Typical V.35 Interface
LTC1344 RECEIVER LTC1343
Figure V.28 Receiver Configuration
Figure V.35 Receiver Configuration
V.35 Interface
typical V.35 balanced interface shown Figure V.35 differential generator with outputs ground connected differential receiver with ground input connected input connected V.35 interface requires delta network termination receiver generator end. receiver differential impedance measured connector must ±10, impedance between shorted terminals ground (C') ±15. V.35 mode, both switches inside LTC1344 connecting T-network impedance, shown Figure Both switches LTC1343 off. input impedance receiver placed parallel with T-network termination, does affect overall input impedance significantly. generator differential impedance must 150, impedance between shorted terminals ground ±15. generator termination, switches both
side center resistor brought bypassed with external capacitor reduce common mode noise, shown Figure mismatch driver rise fall times skew driver propagation delays will force current through center termination resistor ground, causing high frequency common mode spike terminals. This spike cause problems that reduced capacitor which shunts much common mode energy ground rather than down cable.
LTC1344 V.35 DRIVER
51.5
51.5 100pF
Figure V.35 Driver Using LTC1344
AN87-25
Application Note
Table LTC1343/LTC1344 Mode Selection
LTC1343 Mode Name V.10/RS423 RS530A clock data RS530A control Reserved X.21 V.35 clock data V.35 control RS530/RS449/V.36 V.28/RS232 Cable CTRL/ V.10 V.10 V.10 V.10 V.10 V.28 V.28 V.10 V.28 V.10 V.11 V.11 V.11 V.11 V.35 V.28 V.11 V.28 V.10 V.11 V.11 V.35 V.28 V.11 V.10 V.11 V.11 V.11 V.11 V.35 V.28 V.11 V.28 V.10 V.11 V.11 V.11 V.11 V.35 V.28 V.11 V.28 V.10 V.11 V.10 V.11 V.11 V.35 V.28 V.11 V.28 V.10 V.11 V.11 V.11 V.11 V.35 V.28 V.11 V.28 V.10 V.10 V.10 V.10 V.10 V.28 V.28 V.10 V.28
LATCH LTC1344 DCE/ (DATA) LTC1343 DCE/DTE CTRL/CLK LATCH (DATA)
CONNECTOR CABLE LTC1343 DCE/DTE CTRL/CLK LATCH (DATA)
Figure Mode Selection Cable
AN87-26
Application Note
PORT CONNECTOR DCE/DTE
interface protocol selected simply plugging appropriate interface cable into connector. mode pins routed connector left unconnected wired ground cable, shown Figure pull-up resistors R1-R4 ensure binary when left unconnected also ensure that LTC1343s LTC1344 enter no-cable mode when cable removed. no-cable mode, LTC1343 power supply current drops less than 200µA LTC1343 driver outputs LTC1344 resistive terminators forced into high impedance state. Note that data latch pin, LATCH, shorted ground chips. interface protocol also selected serial controller host microprocessor, shown Figure
LATCH PORT CONNECTOR CONNECTOR DCE/DTE
CONTROLLER
LATCH PORT
DCE/DTE LATCH LATCH LATCH
DCE/DTE
LATCH
Figure Mode Selection Controller
mode selection pins DCE/DTE shared among multiple interface ports, while each port unique data-latch signal that acts write enable. When LATCH low, buffers CTRL/CLK, DCE/DTE, pins transparent. When LATCH pulled high, buffers latch data, changes input pins will longer affect chip. mode selection also accomplished using jumpers connect mode pins ground VCC. Loop-Back LTC1343 contains logic placing interface into loop-back configuration testing. Both loop-back configurations supported. Figure shows complete interface loop-back configuration Figure loop-back configuration. loopback configuration selected pulling low. Enabling Single-Ended Driver Receiver When LTC1343 being used generate control signals (CTRL/CLK high) pulled low, DCE/DTE becomes enable driver receiver their inputs outputs tied together, shown Figure
LTC1343/LTC1344 Mode Selection interface protocol selected using mode select pins CTRL/CLK, summarized Table CTRL/CLK should pulled high LTC1343 being used generate control signals pulled used generate clock data signals. example, port configured V.35 interface, mode selection pins should control signals, CTRL/CLK drivers receivers will operate RS232 (V.28) electrical mode. clock data signals, CTRL/CLK drivers receivers will operate V.35 electrical mode, except single-ended driver receiver, which will operate RS232 (V.28) electrical mode. DCE/DTE will configure port mode when high, when low.
AN87-27
Application Note
SERIAL CONTROLLER LTC1343 LTC1344 LTC1344 LTC1343 SERIAL CONTROLLER
SCTE
SCTE
SCTE
SCTE
CTRL/CLK DCE/DTE
DCE/DTE LATCH
CTRL/CLK DCE/DTE LATCH DCE/DTE
LATCH
LTC1343
LTC1343
LATCH
CTRL/CLK
CTRL/CLK
DCE/DTE
DCE/DTE
LATCH
Figure Normal Loop-Back
Figure Normal Loop-Back
AN87-28
LATCH
Application Note
LTC1343 DCE/DTE CTRL/CLK
control chip share signal connector With CTRL/CLK high, DCE/DTE becomes enable signal. Single-ended receiver connected implement (ring indicate) signal RS232 mode (see Figure 45). other modes, carries DSR(B) signal. cable selectable multiprotocol interface shown Figure Control signals implemented. supply select lines brought connector. mode selected cable wiring (connector (connector DCE/DTE (connector ground (connector letting them float. DCE/DTE floating, pull-up resistors will pull signals VCC. select hard wired VCC. When cable pulled out, interface goes into no-cable mode. cable-selectable multiprotocol interface found many popular data routers shown Figure entire interface, including signal, implemented using tiny µDB-26 connector. Conclusion LTC1343 LTC1344 allow designer multiprotocol serial interface spend time software rather than hardware. Simply drop chips down board, hook them connector serial controller, apply supply voltage you're running. addition, chip set's small size unique termination topology allow many ports placed board using inexpensive connectors cables.
Figure Single-Ended Driver Receiver Enable
affect configuration when CTRL/ high except allow DCE/DTE become enable. When DCE/DTE low, driver output enabled. receiver output goes into three-state, input presents load ground. When DCE/DTE high, driver output goes into threestate, receiver output enabled. receiver input presents load ground modes except when configured RS232 operation, when input impedance ground. Multiprotocol Interface with DB-25 µDB-26 Connectors multiprotocol serial interface with standard DB-25 connector EIA-530 configuration shown Figure (Figures 44-47 follow 30-33). signal lines must reversed cable when switching between using same connector. example, mode, signal routed receiver mode, signal routed receiver interface mode selected logic outputs from controller from jumpers either mode-select pins. single-ended driver receiver
AN87-29
Application Note
100pF 100pF 100pF
DTE_LL/DCE_DTE_TXD/DCE_RXD DTE_SCTE/DEC_RXC LTC1343 CHARGE PUMP 3.3µF
LTC1344
DCE/
DB-25 CONNECTOR
DTE_TXC/DCE_TXC DTE_RXC/DCE_SCTE DTE_RXD/DCE_TXD DTE_TM/DCE_LL
CTRL LATCH INVERT 100k LTC1343
CHARGE PUMP
DTE_RL/DCE_RL DTE_RTS/DCE_CTS DTE_DTR/DCE_DSR
DTE_DCD/DCE_DCD DTE_DSR/DCE_DTR DTE_CTS/DCE_RTS
LATCH
100k DCE/DTE
CTRL LATCH INVERT
Figure Controller-Selectable Multiprotocol DTE/DCE Port with DB-25 Connector
AN87-30
SCTE SCTE
SCTE SCTE
SGND SHIELD
3.3µF
Application Note
100pF 100pF 100pF
LTC1343 CHARGE PUMP 3.3µF
LTC1344
SCTE
100k
CTRL LATCH INVERT
LTC1343 CHARGE PUMP
RIEN RS232 (106) (107) B/RI (125) (109)
LATCH
100k
CTRL LATCH INVERT
Figure Controller-Selectable Multiprotocol Port with Ring-Indicate DB-25 Connector
DCE/
DB-25 FEMALE CONNECTOR
(142) (104) (115) (114)
SCTE (113) SCTE (103) (141)
SGND (102) SHIELD (101)
3.3µF
(108) (105) (140)
AN87-31
Application Note
100pF 100pF 100pF
LTC1343 CHARGE PUMP 3.3µF
LTC1344
DTE_TXD/DCE_RXD DTE_SCTE/DEC_RXC
DTE_TXC/DCE_TXC DTE_RXC/DCE_SCTE DTE_RXD/DCE_TXD
CTRL LATCH INVERT 100k LTC1343
CHARGE PUMP
DTE_RTS/DCE_CTS DTE_DTR/DCE_DSR
DTE_DCD/DCE_DCD DTE_DSR/DCE_DTR DTE_CTS/ DCE_RTS
100k
CTRL LATCH INVERT
Figure Cable-Selectable Multiprotocol DTE/DCE Port with DB-25 Connector
AN87-32
DCE/
DB-25 CONNECTOR
SCTE SCTE
SCTE SCTE
SGND SHIELD
3.3µF
DCE/DTE
CABLE WIRING MODE SELECTION MODE V.35 EIA-530, RS449, V.36, X.21 RS232
CABLE WIRING DTE/DCE SELECTION MODE
Application Note
100pF 100pF 100pF
LTC1343 CHARGE PUMP 3.3µF
LTC1344
DTE_TXD/DCE_RXD DTE_SCTE/DEC_RXC
DTE_TXC/DCE_TXC DTE_RXC/DCE_SCTE DTE_RXD/DCE_TXD
CTRL LATCH INVERT 100k DTE_LL/DCE_LL DTE_RTS/DCE_CTS DTE_DTR/DCE_DSR LTC1343
CHARGE PUMP
DTE_DCD/DCE_DCD DTE_DSR/DCE_DTR DTE_CTS/DCE_RTS
100k
CTRL LATCH INVERT
Figure Cable-Selectable Multiprotocol DTE/DCE Port with µDB-26 Connector
DCE/
µDB-26 CONNECTOR
SCTE SCTE
SCTE SCTE
SGND SHIELD
3.3µF
DCE/DTE
CABLE WIRING MODE SELECTION MODE V.35 EIA-530, RS449, V.36, X.21 RS232
CABLE WIRING DTE/DCE SELECTION MODE
AN87-33
Application Note
LT1328: COST IRDA RECEIVER SOLUTION DATA RATES 4MBPS Alexander Strong IrDA LT1328 circuit Figure operates over full meter range IrDA standard stipulated light levels. IrDA data rates 115kbps below, 1.6µs pulse width used zero pulse one. Light levels 40mW/sr (milliwatts steradian) 500mW/ Figure shows scope photo transmitter input (top trace) LT1328 output (bottom trace). Note that input transmitter inverted; that transmitted light produces high input, which results zero output transmitter. Mode (pin should high these data rates. IrDA- compatible transmitter also implemented with only components, shown Figure Power requirements LT1328 minimal: single supply quiescent current.
1000pF VBIAS HIGH 4PPM
HSDL-4220 1/2W TRANSMIT INPUT DRIVER 2N7002 2N7002
1328_02.eps
Figure IrDA Transmitter
IrDA second fastest tier IrDA standard addresses 576kbps 1.152Mbps data rates, with pulse widths interval zero pulse one. 1.152Mbps rate, example, uses pulse width 217ns; total time 870ns. Light levels 100mW/sr 500mW/sr over meter range. photo transmitted input LT1328 output shown Figure LT1328 output pulse width will less than 800ns wide over above conditions 1.152Mbps. should held these data rates above. 4ppm last IrDA encoding method 4Mbps uses pulse position modulation, thus name: 4ppm. bits encoded location 125ns wide pulse four positions within 500ns interval bits 1/500ns 4Mbps). Range input levels same 1.152Mbps. Figure shows LT1328 reproduction this modulation.
FILT LIGHT BPU22NF TEMIC 10nF FILT 330pF LT1328
MODE
(5V) 0.1µF
10µF
DATA
DATA
Figure LT1328 IrDA Receiver-Typical Application
TRANSMITTER INPUT
TRANSMITTER INPUT
LT1328 OUTPUT
LT1328 OUTPUT
2µs/DIV
200ns/DIV
Figure IrDA 115kbps Modulation
Figure IrDA 1.152Mbps Modulation
AN87-34
Application Note
BIAS
TRANSMITTER INPUT
PHOTODIODE PREAMP
VBIAS
LT1328 OUTPUT
200ns/DIV
FILTER 330pF 10nF CELL
Figure IrDA 4ppm Modulation
MODE
LT1328 Functional Description Figure block diagram LT1328. Photodiode current from transformed into voltage feedback resistor RFB. level preamp held VBIAS servo action transconductance amplifier's servo action only suppresses frequencies below Rgm/CFILT pole. This highpass filtering attenuates interfering signals, such sunlight incandescent fluorescent lamps, selectable high data rates. high data rates, should held low. highpass filter breakpoint capacitor 25/(2 where 60k. 330pF capacitor (C1) sets 200kHz corner frequency used data rates above 115kbps. data rates (115kbps below), capacitance increased taking high. This switches parallel with lowering highpass filter breakpoint. 10nF (C2) produces 6.6kHz corner. Signals processed preamp/gm amplifier combination cause comparator output swing low.
FILTER
DATA
COMPARATOR
Figure LT1328 Block Diagram
Conclusion summary, LT1328 used build cost receiver compatible with IrDA standards. ease flexibility also allow provide solutions numerous other photodiode receiver applications. tiny MSOP package saves board area.
AN87-35
Application Note
LTC1387 SINGLE RS232/RS485 MULTIPROTOCOL TRANSCEIVER Y.K. Introduction
INTERFACE LTC1387 RS232 RS485 RS232 RS485 CONTROLLER
LTC1387 single supply, logic-configurable, single-port RS232 RS485 transceiver. LTC1387 offers flexible combination RS232 drivers, RS232 receivers, RS485 driver, RS485 receiver onboard charge pump generate boosted voltages true RS232 levels from single supply. RS232 transceivers RS485 transceiver designed share same port pins both single-ended differential signal communication modes. RS232 transceiver supports both RS232 EIA562 standards, whereas RS485 transceiver supports both RS485 RS422 standards. Both half-duplex full-duplex communication supported.
**TX2A-5V (DPST)
DZ/SLEW RXEN DXEN 485/232
RXEN DXEN MODE
ZETEX AROMAT RS232 MODE RXEN DXEN MODE
7.5k *FMMT619 (516) 543-7100 (908) 464-3550
1387_02.eps
RS485 TRANSMIT MODE RXEN DXEN MODE
RS485 RECEIVE MODE RXEN DXEN MODE
SHUTDOWN MODE RXEN DXEN MODE
Figure Full-Duplex RS232, Half-Duplex RS485
INTERFACE LTC1387 RS232 RS485 RS485 RS485 RS232 RS485 RS485 CONTROLLER INTERFACE RS232 RS485 LTC1387 CONTROLLER
DZ/SLEW RXEN DXEN 485/232
DZ/SLEW
RXEN DXEN MODE
RXEN DXEN 485/232
RXEN DXEN MODE
1387_01.eps
1387_03.eps
RS232 TRANSMIT MODE RXEN DXEN MODE
RS232 RECEIVE MODE RXEN DXEN MODE
RS485 TRANSMIT MODE RXEN DXEN MODE
RS485 RECEIVE MODE RXEN DXEN MODE
SHUTDOWN MODE RXEN DXEN MODE
RS232 MODE RXEN DXEN MODE
RS485 MODE RXEN DXEN MODE
SHUTDOWN MODE RXEN DXEN MODE
Figure Half-Duplex RS232, Half-Duplex RS485
Figure Full-Duplex RS232 (1-Channel), Full-Duplex RS422
AN87-36
Application Note
logic input selects between RS485 RS232 modes. Three additional control inputs allow LTC1387 reconfigured easily software adapt various communication needs, including one-signal line RS232 mode (see function tables figures). Four examples interface port connections shown Figures 54-57. SLEW input pin, active RS485 mode, changes driver transition between normal slow slew-rate modes. normal RS485 slew mode, twisted pair cable must terminated both ends minimized signal reflection. slow-slew mode, maximum signal bandwidth reduced, minimizing signal reflection problems. Slow-slew-rate systems often improperly terminated even unterminated cables with acceptable results. cable termination required, external termination resistors connected through switches relays. LTC1387 features micropower shutdown mode, loopback mode self-test, high data rates (120kbaud RS232 5Mbaud RS485) protection driver outputs receiver inputs.
INTERFACE RS232 RS485 RS232 RS485 RS232 RS485 RS232 RS485 DZ/SLEW RXEN DXEN 485/232 DX2/SLEW RXEN DXEN MODE TERMINATE
1387_04.eps
LTC1387
CONTROLLER
RS232 MODE RXEN DXEN MODE
RS485 MODE RXEN DXEN MODE
SHUTDOWN MODE RXEN DXEN MODE
Figure Full-Duplex RS232 (2-Channel), Full-Duplex RS485 with Slew Termination Control
10MB/s MULTIPLE-PROTOCOL CHIP SUPPORTS NET1 NET2 STANDARDS
David
Introduction Typical Application Like LTC1343 software-selectable multiprotocol transceiver, introduced August, 1996 issue Linear Technology LTC1543/LTC1544/LTC1344A chip creates complete software-selectable serial interface using inexpensive DB-25 connector. main difference between these parts division functions: LTC1343 configured data/clock chip control-signal chip using CTRL/CLK pin, whereas
LTC1543 dedicated data/clock chip LTC1544 control-signal chip. chip supports V.28 (RS232), V.35, V.36, RS449, EIA-530, EIA-530A X.21 protocols either mode. Figure shows typical application using LTC1543, LTC1544 LTC1344A. just mapping chip pins connector, design interface port complete. figure shows mode connection DB-25 connector. LTC1543 contains three drivers three receivers, whereas LTC1544 contains four drivers four receivers. LTC1344A contains switchable resistive terminators that connected only high speed clock data signals. When interface protocol changed mode selection pins,
AN87-37
Application Note
Table Mode-Pin Functions
LTC1543/LTC1544 Mode Name Used EIA-530A EIA-530 X.21 V.35 RS449/V.36 RS232/V.28 Cable
Cable-Selectable Multiprotocol Interface interface protocol selected simply plugging appropriate interface cable into connector. cableselectable multiprotocol DTE/DCE interface shown Figure mode pins routed connector left unconnected wired ground cable. internal pull-up current sources ensure binary when left unconnected also ensure that LTC1543/LTC1544/LTC1344A enter no-cable mode when cable removed. no-cable mode, LTC1543/LTC1544 power supply current drops less than 200µA LTC1543/LTC1544 driver outputs will forced into high impedance state. Adding Optional Test Signal some cases, optional test signals local loopback (LL), remote loopback (RL) test mode (TM) required there enough drivers receivers available LTC1543/LTC1544 handle these extra signals. solution combine LTC1544 with LTC1343. using LTC1343 handle clock data signals, chip gains extra single-ended driver/receiver pair. This configuration shown Figure Compliance Testing European standard 45001 test report available LTC1543/LTC1544/LTC1344A chip set. report provides documentation compliance chip Layer NET1 NET2 standard. copy this test report available from from Detecon, Inc. 1175 Highway Paul, 55112. Conclusion world network equipment, product differentiation mostly software serial interface. LTC1543, LTC1544 LTC1344A provide simple comprehensive solution standards compliance multiple-protocol serial interface.
drivers, receivers line terminators placed their proper configuration. mode functions summarized Table There internal 50µA pull-up current sources mode select pins, DCE/DTE INVERT pins.
Operation LTC1543/LTC1544/LTC1344A chip configured either operation ways. first when chip dedicated port with connector appropriate gender. second when port connector that configured operation rerouting signals chip using dedicated cable. Figure example dedicated port using female DB-25 connector. complement this port DTE-only port using male DB-25 connector, shown Figure port must accommodate both modes, mapping drivers receivers connector pins must change accordingly. example, Figure driver LTC1543 connected DB-25 connector. mode, shown Figure driver mapped pins DB-25 connector. port that configured either operation shown Figure This configuration requires separate cables proper signal routing.
AN87-38
Application Note
100pF 100pF 100pF
LTC1543 CHARGE PUMP 3.3µF
LTC1344A
LATCH
DCE/DTE
(104) (115)
SCTE
DCE/DTE
LTC1544
INVERT
DCE/DTE
Figure Controller-Selectable Port with DB-25 Connector
(114) SCTE (113) SCTE (103) SGND (102) SHIELD (101)
DB-25 FEMALE CONNECTOR
(106) (107)
(109) (108) (105) (141)
AN87-39
Application Note
100pF 100pF 100pF
SCTE LTC1543 CHARGE PUMP 3.3µF
LTC1344A
LATCH
DCE/DTE
(103) SCTE (113) SCTE
DCE/DTE
LTC1544
INVERT
DCE/DTE
Figure Controller-Selectable Multiprotocol Port with DB-25 Connector
AN87-40
(114) (115) (104) SHIELD
DB-25 MALE CONNECTOR
(105) (108)
(109) (107) (106) (141)
Application Note
100pF 100pF 100pF
DTE_TXD/DCE_RXD DTE_SCTE/DCE_RXC LTC1543 CHARGE PUMP 3.3µF
LTC1344A
LATCH
DCE/DTE
SCTE SCTE
DTE_TXC/DCE_TXC
DTE_RXC/DCE_SCTE
DTE_RXD/DCE_TXD
DCE/DTE
DTE_RTS/DCE_CTS
DTE_DTR/DCE_DSR
LTC1544
DTE_DCD/DCE_DCD DTE_DSR/DCE_DTR
DTE_CTS/DCE_RTS
DTE_LL/DCE_LL
INVERT
DCE/DTE
DCE/DTE
Figure Controller-Selectable DTE/DCE Port with DB-25 Connector
SHIELD
SCTE SCTE
DB-25 CONNECTOR
AN87-41
Application Note
100pF 100pF 100pF
DTE_TXD/DCE_RXD DTE_SCTE/DCE_RXC LTC1543 CHARGE PUMP 3.3µF
LTC1344A
LATCH
DCE/DTE
SCTE SCTE
SHIELD DB-25 CONNECTOR SCTE SCTE DCE/DTE
DTE_TXC/DCE_TXC
DTE_RXC/DCE_SCTE
DTE_RXD/DCE_TXD
DCE/DTE
DTE_RTS/DCE_CTS
DTE_DTR/DCE_DSR
LTC1544 CABLE WIRING MODE SELECTION MODE V.35 RS449, V.36 RS232 CABLE WIRING DTE/DCE SELECTION MODE
DTE_DCD/DCE_DCD DTE_DSR/DCE_DTR
DTE_CTS/DCE_RTS
DCE/DTE INVERT
Figure Cable-Selectable Multiprotocol DTE/DCE Port
AN87-42
Application Note
100pF 100pF 100pF
LTC1343 DTE_TXD/DCE_RXD DTE_SCTE/DCE_RXC DTE_RTS/DCE_CTS CHARGE PUMP 3.3µF
LTC1344A
LATCH
DCE/DTE
DTE_LL/DCE_
SCTE SCTE
DTE_TXC/DCE_TXC
DTE_RXC/DCE_SCTE
DTE_RXD/DCE_TXD
DTE_TM/DCE_LL
100k CTRL LATCH
INVERT 423SET
DTE_DTR/DCE_DSR
LTC1544
DTE_DCD/DCE_DCD DTE_DSR/DCE_DTR
DTE_CTS/DCE_RTS
DTE_RL/DCE_RL
INVERT
DCE/DTE
DCE/DTE
Figure Controller-Selectable Multiprotocol DTE/DCE Port with RLL, DB-25 Connector
SHIELD
SCTE SCTE
DB-25 CONNECTOR
AN87-43
Application Note
NET1 NET2 SERIAL INTERFACE CHIP SUPPORTS TEST MODE David Some serial networks test mode exercise circuits interface. network divided into local remote data terminal equipment (DTE) datacircuit-terminating equipment (DCE), shown Figure Once network placed test mode, local will transmit driver circuits expect receive same signals back from either local remote DCE. These tests called local remote loopback. LTC1543/LTC1544/LTC1344A chip taken integrated approach multiple protocol. using this chip set, Net1 Net2 design work done. LTC1545 extends family offering test mode capability. replacing 6-circuit LTC1544 with 9-circuit LTC1545, optional circuits (Test Mode), (Remote Loopback) (Local Loopback) implemented. Figure shows typical application using LTC1543, LTC1545 LTC1344A. just mapping chip pins connector, design interface port complete. chip supports V.28, V.35, V.36, RS449, EIA530, EIA-530A X.21 protocols either mode. Shown here mode connection DB-25 connector. mode-select pins, used select interface protocol, summarized Table
Table Mode-Pin Functions
LTC1543/LTC1544 Mode Name Used EIA-530A EIA-530
LOCAL LOCAL REMOTE REMOTE
X.21 V.35 RS449/V.36 RS232/V.28 Cable
Figure Serial Network
AN87-44
Application Note
Just marker
LTC1543 CHARGE PUMP 3.3µF DCE/DTE LATCH 100pF 100pF 100pF
LTC1344A
SCTE
DCE/DTE
LTC1544
INVERT
DCE/DTE
Figure Typical Application: Controller-Selectable Port with DB-25 Connector
(104) (115)
(114) SCTE (113) SCTE (103) SGND (102) SHIELD (101)
DB-25 FEMALE CONNECTOR
(106) (107)
(109) (108) (105) (141)
1544
AN87-45
Application Note
Operational Amplifiers/Video Amplifiers LT1490/LT1491 OVER-THE-TOP DUAL QUAD MICROPOWER RAIL-TO-RAIL AMPS Coelho-Sousae Introduction LT1490 Linear Technology's lowest power, lowest cost smallest dual rail-to-rail input output operational amplifier. ability operate with inputs above VCC, high performance-to-price ratio availability MSOP package, sets LT1490 apart from other amplifiers. Over-the-Top Application battery current monitor circuit shown Figure demonstrates LT1491's ability operate with inputs above positive supply rail. this application,
CHARGER VOLTAGE 1N4001
conventional amplifier would limited battery voltage between ground, LT1491 handle battery voltages high 44V. LT1491 shut down removing VCC. With removed input leakage less than 0.1nA. damage LT1491 will result from inserting battery backward. When battery charging, senses voltage drop across output causes drain sufficient current through balance inputs Likewise, form closed loop when battery discharging. current through proportional current this current flows into which converts back voltage. buffers amplifies voltage across compares output determine polarity current through scale factor VOUT with open 1V/A. With closed scale factor 100mA, current measured.
VBATTERY
LT1491
2N3904
LT1491
LOGIC
LT1491
2N3904
VSUPPLY
LOGIC HIGH (5V) CHARGING LOGIC (0V) DISCHARGING
LT1491 90.9k
VOUT
IBATTERY
NOTE:
(VOUT) (RS) (RG/RA) GAIN
VOUT GAIN
AMPS
OPEN, GAIN CLOSED, GAIN
Figure LT1491 Battery Current Monitor-an "Over-The-Top" Application
AN87-46
Application Note
LT1210: 1-AMPERE, 35MHz CURRENT FEEDBACK AMPLIFIER William Jett Mitchell Introduction LT1210 current feedback amplifier extends Linear Technology's high speed driver solutions ampere level. device combines 35MHz bandwidth with guaranteed output current, operation with ±15V supplies optional compensation capacitive loads, making well suited driving impedance loads. Short circuit protection thermal shutdown ensure device's ruggedness. shutdown feature allows device
switched into high impedance, current mode, reducing dissipation when device use. LT1210 available 7-pin TO-220 package, 7-pin surface mount package 16-pin SO-16 surface mount package. Twisted Pair Driver Figure shows transformer-coupled application LT1210 driving twisted pair. This surge impedance typical PVC-insulated, gauge, telephonegrade twisted pair wiring. transformer ratio allows just over reach twisted pair full output. Resistor acts primary side back-termination.
4.7µF* 100nF
INPUT
LT1210
2.5W 100, 2.5W
4.7µF* -15V 100nF *TANTALUM MIDCOM 671-7783 EQUIVALENT
INPUT
Figure Bridge Configuration, LT1210 Deliver Almost Twisted Pair (and Another Back Termination)
Figure Twisted Pair Easily Driven Applications Such ADSL. Voltage Gain About 5VP-P Input Corresponds Full Output
LT1210
2.5W
100,
LT1210 2.5W -15V MIDCOM 671-7783 EQUIVALENT
AN87-47
Application Note
INPUT 5VPP INPUT 5VPP 10nF -15V -15V 2.5W 330nF 2.5W
LT1210
LT1210
10nF
COILTRONICS VERSA-PAC CTX-01-13033-X2
COILTRONICS VERSA-PAC CTX-01-13033-X2
Figure Matched Load with Balun-Mode Transformer, this Circuit Delivers Measured 35.6dBm (almost 4W). Full-Power Band Limits 15kHz Slightly Over 10MHz
Figure Wide Bandwidth Obtained with Even Higher Impedance Transformations. Here, Step-Up Matches Develops Nearly 4.5W. Measured +33dBm Reaches Load. Full-Power Band Limits 80kHz 18MHz
overall frequency response flat within from 500Hz 2MHz. Distortion products 1MHz below -70dBc total output power 560mW (load plus termination), rising -56dBc 2.25W. ±15V supply, maximum output power available when load presented LT1210. With transformer shown Figure total load impedance approximately limits output 2.25W. Bridging allows nearly maximum output power delivered into standard data communications transformers. Figure shows bridged application with LT1210s, delivering approximately maximum into load termination. first glance resistor values would suggest gain imbalance between inverting noninverting sides bridge. close inspection, however, apparent that both sides operate closed loop gain relative input signal. This ensures symmetric swing maximum undistorted output. Matching Systems practical systems exhibit impedance, matching transformer necessary applications driving other loads, such Multifilar winding techniques exhibit best high frequency characteristics.
Suitable off-the-shelf components available, such Coiltronics Versa-Pacseries. These hexafilar wound give power bandwidths excess 10MHz. disadvantage that using limited number windings makes impossible exactly transform optimum load. Nevertheless, there several useful connections. Figure windings configured step-up, reflecting 12.5 into LT1210. circuit exhibits 18dB gain drives nearly +36dBm. large-signal, frequency response limited magnetizing inductance transformer about 15kHz. high frequency response limited 10MHz stack four secondary windings. Reconfiguring transformer windings allows double termination full power (Figure 69). Here transformer reflects 11.1 amplifier delivers over +33dBm load. Paralleled input windings limit frequency response 80kHz, fewer series secondary windings extend high frequency corner 18MHz. coupling capacitor shown these examples added block current flow through transformer primary, arising from amplifier offsets. capacitor value based setting equal reflected load impedance
AN87-48
Application Note
INPUT 5VP-P GAIN (dB) 10nF 100nF 0.01 10.0 FREQUENCY (MHz)
LT1210
Figure this Bridge Amplifier, LT1210 Delivers +39.5dBm (9W) Load. Power Band Limits Range from 40kHz 14.5MHz. Sixth, Otherwise-Unused Winding Connected Parallel with Secondary Winding Avoid Parasitic Effects Arising from Floating Winding.
frequency where primary also equal reflected load. This isolates amplifier from impedance short frequencies below transformer cutoff. applications where termination resistor positioned between LT1210 amplifier transformer, coupling capacitor necessary. Note that frequency signal, well below transformer's cutoff frequency, could result high dissipation termination resistor.
-15V
LT1210 10nF
Figure Frequency Response Figure 70's Circuit
CTX-01-13033-X2 VERSA-PAC
Another useful connection Versa-Pac transformer shown Figure transformation presents 11.1 each LT1210 bridge, delivering whopping into this circuit lower frequency cutoff limited choice coupling capacitor approximately 40kHz (the transformer capable 15kHz). frequency response shown Figure Conclusion LT1210 combines high output current with high slew rate form effective solution driving impedance loads. Power levels supplied load frequencies ranging from beyond 10MHz.
AN87-49
Application Note
LT1207: ELEGANT DUAL 60MHZ, 250mA CURRENT FEEDBACK AMPLIFIER Applications Staff Introduction LT1207 dual version Linear Technology's LT1206 current feedback amplifier. Each amplifier 60MHz bandwidth, guaranteed 250mA output current, operates ±15V supply voltages offers optional external compensation driving capacitive loads. These features capabilities combine make well suited such difficult applications driving cable loads, wide-bandwidth video high speed digital communication. LT1088 Differential Front Using thermal conversion, LT1088 wideband RMS/DC converter effective solution applications such voltmeters, wideband AGC, leveling loops high frequency noise measurements. thermal conversion method achieves vastly wider bandwidth than other approach. handle input signals that have 300MHz bandwidth crest factor least 40:1. thermal technique employed relies first principles: wave form's value defined heating value load. Another characteristic LT1088 impedance inputs 250), common thermal converters. Though this impedance represents difficult load most drive circuits, LT1207 handle with ease. Featuring high input impedance overload protection, differential input, wideband thermal RMS/DC converter Figure performs true RMS/DC conversion over 10MHz bandwidth with less than error, independent input-signal wave shape. circuit consists wideband input amplifier, RMS/DC converter overload protection.1 LT1207 provides high input impedance, gain output current capability necessary drive LT1088's input heater. 5k/24pF network across LT1207's gain-set resistor used adjust slight peaking characteristic high frequencies, ensuring flatness 10MHz. converter uses matched pairs heaters diodes control amplifier. produces heat when LT1207 drives differentially. This heat lowers D1's voltage. Differentially connected responds driving heating closing loop. A3's output directly relates input signal's value, regardless input frequency wave shape. A4's gain trim compensates residual LT1088 mismatches. network around frequency compensates loop, ensuring good settling time. LT1088 suffer damage input driven beyond 9VRMS 100% duty cycle. easy remedy this possibility reduce driver supply voltage. This, however, sacrifices crest factor. Instead, means overload protection included. LT1018 monitors D1's anode voltage. Should this voltage become abnormally low, A5's output goes pulls A6's input low. This causes A6's output high, shutting down LT1207 eliminating overload condition. network A6's input delays LT1207's reactivation. overload condition remains, shutdown reinstated. This oscillatory action continues, protecting LT1088 until overload corrected. RMS/DC circuit's error bandwidth CMRR performance shown Figures respectively. Clock Driver Charge-coupled-devices (CCDs) used many imaging applications, such surveillance, hand-held desktop computer video cameras, document scanners. Using "bucket-brigade," CCDs require precise multiphase clock signal initiate transfer lightgenerated pixel charge from charge reservoir next. Noise, ringing overshoot clock signal must avoided, since they introduce errors into output signal. These errors cause aberrations perturbations displayed printed image. challenges surface effort avoid these error sources when driving CCD's input. First, CCDs have input capacitance that varies over range 100pF 2000pF varies directly with number sensing elements (pixels). This presents high capacitive load clock-drive circuitry. Second, CCDs typically require clock signal whose magnitude greater than output capabilities interfaces control circuitry.
AN87-50
1.5M 3300pF ZERO TRIM (TRIM OUTPUT) 9.09M 0.1µF 0.1µF 2.7k 2.7k LT1004 1.2V 10µF
0.022µF
0.01µF 9.09M 10µF 0.1µF
LT1207
1,16
LT1078
2N2219
24pF -15V 10µF 0.1µF 0.1µF 10MHz TRIM LT1088 FULL-SCALE TRIM
0.1µF
LT1078
VOUT
-15V
0.1µF
LT1207 0.1µF
1N914 LT1018
510k
10µF
0.1µF
0.1µF -15V 4.7k -15V LT1004 1.2V
Figure Differential Input 10MHz RMS/DC Converter Accuracy, High Input Impedance Overload Protection.
LT1018
Application Note
AN87-51
Application Note
COMMON MODE REJECTION RATIO, 5VRMS ERROR >>1000:1 1000:1 900:1 800:1 700:1 600:1 500:1 400:1 300:1 200:1 100:1 FREQUENCY (MHz) ERROR POINT 10.2MHz
-0.5
-1.0 FREQUENCY (MHz)
Figure Error Plot Differential-Input RMS/DC Converter. Gain Boost Preserves Accuracy Causes Slight Peaking before Roll-Off. Boost Maximum Bandwidth Minimum Error
Figure Common Mode Rejection Ratio Frequency Differential-Input RMS/DC Converter. Layout, Amplifier Bandwidth Matching Characteristics Determine Curve
10µF 45pF
0.1µF
180pF
91pF
SIMULATED ARRAY LOAD
1,16 0.1µF 0.1µF 3300pF
2MHz 74HC74 500kHz 500kHz
LT1207
10µF -10V 510k
10µF 45pF
0.1µF
180pF
91pF
0.1µF 0.1µF 3300pF
LT1207
10µF -10V 510k
Figure LT1207 Easily Tames High Capacitance Loads Clock Inputs without Ringing Overshoot
AN87-52
Application Note
Figure 76a. Trace Quadrature Drive Signals. Trace Voltage Input Simulated Figure Driven Logic
Figure 76b. Trace Quadrature Signals. Trace Shows Voltage Input Simulated Figure Driven LT1207
amplifying filter built around LT1207 will meet both challenges. Controlling clock signal rise fall times avoid ringing overshoot. This done conditioning clock signal with nonringing Gaussian filter. circuit shown Figure uses LT1207 filter amplify control circuitry clock output signals. reduce ringing overshoot, each amplifier configured third-order Gaussian lowpass filter with 1.6MHz cutoff frequency. Figures compare response digital clock-drive signal output LT1207, each driving 3300pF load. digital clock circuit
major weaknesses that lead jitter image distortion. CCD's output changing during charge transfer, producing glitches that decay exponentially. Conversely, LT1207 circuit's output flat controlled rise fall. used sample output, conversion will much more accurate when LT1207 circuit used clock pixel changes. With LT1207's filter configuration, output controlled rise fall time approximately 300ns. Ringing overshoot absent from LT1207's output. Wide bandwidth, high output current capability external compensation allow LT1207 easily drive difficult load CCD's clock input.
Thanks Williams this Circuit
AN87-53
Application Note
MICROPOWER, DUAL QUAD JFET AMPS FEATURE C-LOAD CAPABILITY PICOAMPERE INPUT BIAS CURRENTS Alexander Strong Introduction LT1462/LT1464 duals LT1463/LT1465 quads first micropower amps (30µA typical, 40µA maximum LT1462; 140µA typical, 200µA maximum LT1464) offer both pico ampere input bias currents (500fA typical) unity-gain stability capacitive loads 10nF. outputs swing load within volts either supply. Just like amps that require order magnitude more supply current, LT1462/LT1463 LT1464/ LT1465 have open loop gains 600,000 1,000,000, respectively. These unique features, along with 0.8mV offset, have been incorporated into single monolithic amplifier before. Applications Figure track-and-hold circuit that uses cost optocoupler switch. Leakages these parts usually nano region with volts across output. Since there less than across junctions, less than 0.5pA leakage achieved both optocouplers. input signal buffered while other buffers stored voltage; this results droop 50µV/s with 10nF cap. Figure logging photodiode sensor using LT1462 duals LT1463 quad. input bias current LT1462/LT1463 makes natural amplifying level signals from high impedance transducers. 500fA input bias current contributes only 0.4fA/Hz current noise. example, input impedance converts noise current noise voltage only 0.4nV/Hz. Here, photodiode converts light
LTC201
MCT2
10nF POLYSTYRENE
LT1464
LTC201
MCT2
0.5pA 0.05mV/SEC. 10nF TOTAL SUPPLY CURRENT 460µA MAX. ±15V SUPPLIES, SUPPLIES TYPICAL DROOP
FUNCTION TRACK HOLD POSITIVE PEAK DETECTOR NEGATIVE PEAK DETECTOR
MODE TRACK RESET RESET
MODE HOLD STORE STORE
LTC201 SWITCH OPEN LOGIC
Figure Low-Droop Track-and-Hold Circuit/Peak Detector
AN87-54
VOUT
LT1464
1464_02.eps
Application Note
100k 1N4148 2N3904
PHOTODIODE
current, which converted voltage first amp. first, second third gain stages logarithmic amplifiers that perform logarithmic compression. feedback path comprising active only no-light conditions, which very rare, picoampere sensitivity input. when light present, isolating photodiode from When feedback path needed, small filtered current through keeps output third within acceptable range. third amp's output voltage, which proportional photodiode current, serve logarithmic light meter. Figure shows relationship between output voltage photodiode current. component output third compressed logarithmically passed through capacitor amplitude control. fourth amplifies this signal which generated across R13. logarithmic compression photodiode current allows user examine signals wide range input currents.
OUTPUT
LT1462
200pF
LT1462
200pF
LT1462
0.47µF
1N4148
1N4148
10µF
LT1462
100k
100k
Figure Logging Photodiode Amplifier
1464_03.eps
Conclusion LT1462/LT1464 duals LT1463/LT1465 quads combine many advantages found many different amps, such power, (LT1464/LT1465 140µA, LT1462/LT1463 30µA typical amplifier), wide input common mode range that includes positive rail pico ampere input bias currents. only output swing specified with loads, gain also specified same load conditions, which unheard1.6 PHOTODIODE CURRENT
1464_04.eps
Figure Output Logging Photodiode Amplifier
AN87-55
Application Note
micropower amps. 1MHz (LT1464/LT1465) 250kHz (LT1462/LT1463) bandwidth self adjusts maintain stability capacitive loads 10nF. don't forget 0.8mV offset voltage gains million (LT1464/LT1465) 600,000 (LT1462/LT1463) even with loads.
LT1210: HIGH POWER YIELDS HIGHER VOLTAGE CURRENT Dale Eagar Introduction LT1210, current feedback operational amplifier, opens frontiers. With 30MHz bandwidth, operation ±15V supplies, thermal shutdown output current, this amplifier single-handedly tackles many tough applications. handle output voltages higher than ±15V currents greater than ampere? This Design Idea features collection circuits that open door high voltage high current LT1210. Fast Sassy-Telescoping Amplifiers Need ±30V? Cascading LT1210's will there. This circuit (Figure will provide ±30V 13MHz full-power bandwidth (see Figure 81). does work? first LT1210 drives "ground" second LT1210 subcircuit, effectively raising lowering
while second LT1210 further amplifies input signal. This telescoping arrangement cascaded with additional stages more than ±30V. This amplifier stable into capacitive loads, short-circuit protected thermally shuts down when overheated. Extending Power Supply Voltages Another method getting high voltage from amplifier extended-supply mode (see "Extending Supplies More Voltage"; Linear Technology Volume Number (June 1994), 20-22). This involves steering external regulators with power supply pins high voltage amplifier. Figure shows LT1210 connected extendedsupply mode. Placing amplifier extended-supply mode requires changing return compensation node from power supply pins system ground. selected clean step response. process relocating return compensation node slows amplifier down approximately 1MHz (see Figure 83).
INPUT
6.2k
LT1210 0.01µF
OUTPUT
6.2k
LT1210 0.01µF
-15V
-30V
Figure Telescoping Amplifiers
AN87-56
Application Note
LOAD FIGURE 80's +10dBM INPUT LOAD
GAIN (dB)
100K
FREQUENCY (Hz)
Figure Gain Frequency Plot Telescoping Amplifier
Figure 82's circuit will provide ±100V, stable into capacitive loads short-circuit protected. external MOSFETs need heat sinking. Gateway Stars circuit Figure expanded yield much higher voltages; first most obvious higher voltage MOSFETs. This causes problems: first, high voltage P-channel MOSFETs hard get; second, more importantly, power dissipated MOSFETs high single packages. solution build telescoping regulators, shown Figure This circuit provide current ±200V additional power-dissipation ability four MOSFETs. Boosting Output Current current booster detailed Figure illustrates technique amplifying output current capability while maintaining speed. Among many niceties this topology fact that both normally thus consume quiescent current. Once load current reaches approximately 100mA, turns providing additional drive output. This transition seamless outside world takes advantage full speed This circuit's small-signal bandwidth full-power bandwidth shown Figure
Boosting Both Current Voltage current-boosted amplifier shown Figure used replace amplifiers Figure yielding ±10A ±30V. Placing boosted amplifier circuits shown Figures will yield peak powers into kilowatts. Thermal Management When LT1210 used with external transistors increase output voltage and/or current range
100V 100V 100k INPUT IRF640 0.01µF
LT1210 0.01
P6KE
9.1k
LOAD
P6KE
IRF9640
0.01µF 100k -100V -100V
Figure ±100V, Power Driver
AN87-57
Application Note
GAIN (dB) FIGURE 90Vp-p INTO
100K
FREQUENCY (Hz)
Figure Gain Frequency Plot Extended-Supply Amplifier
200V
IRF640 0.1µF INPUT IRF640
0.47µF 250V
additional benefit often realized: system thermal shutdown. Careful analysis thermal design system coordinate overtemperature shutdown LT1210 with junction temperatures external transistors. This essentially extends umbrella protection LT1210's thermal shutdown cover external transistors. thermal shutdown LT1210 activates when junction temperature reaches 150°C about 10°C hysteresis. thermal resistance TO-220 package (LT1210CY) 5°C/Watt).
LT1210 0.01µF
±200V LOAD
0.01µF 0.033 D45VH4 3.6k
9.1k
1.8k
IRF9640
LT1210 0.01 D44VH4
IRF9640 0.47µF 250V
0.01µF 0.033
-200V
-18V
Figure Cascode Power Amplifier
Figure ±10A/1MHz Current-Boosted Power
AN87-58
Application Note
4AP-P INTO LOAD GAIN (dB) LOAD FIGURE +10dBM INPUT
100K FREQUENCY (Hz)
Figure Gain Frequency Response Current-Boosted Amplifier
Summary LT1210 great part; performance terms speed, output current output voltage unsurpassed. C-Loadoutput drive thermal shutdown allow take place real world-no gloves required here. generous output specification LT1210 isn't enough your needs, just couple transistors dissipate additional power your way. Only worldwide supply transistors limits amount power could command with these parts.
RAIL-TO-RAIL AMPLIFIERS: PRECISION PERFORMANCE FROM MICROPOWER HIGH SPEED William Jett Danh Tran Introduction
used both input output signals, maximizing system's dynamic range. Circuits that require signal sensing near positive supply straightforward using rail-to-rail amplifier. Applications
Linear Technology's latest offerings expand range rail-to-rail amplifiers with precision specifications. Railto-rail amplifiers present attractive solution signal conditioning many applications. battery-powered other voltage circuitry, entire supply voltage
6.81k 6.81k 11.3k 330pF 100pF
ability accommodate input output signal that falls within amplifier supply range makes these amplifiers very easy use. following applications demonstrate versatility family amplifiers.
5.23k
47pF
LT1498
5.23k
10.2k 1000pF
LT1498 VOUT
R2R_04.eps
Figure 100kHz Order Butterworth Filter
AN87-59
Application Note
GAIN (dB) -100 -110 100k FREQUENCY (Hz)
R2R_05.eps
20kHz
2.7VP-P
2.7VP-P
NOISE
0.01
0.01
0.001 0.01
AMPLITUDE (VP-P)
R2R_06.eps
0.001
FREQUENCY (Hz)
100k
R2R_07.eps
Figure Filter Frequency Response
Figure Filter Distortion Amplitude
Figure Filter Distortion Frequency
100kHz Order Butterworth Filter Operation
filter shown Figure uses voltage operation wide bandwidth LT1498. Operating inverting mode lowest distortion, output swings rail-to-rail. graphs Figures 88-90 display measured lowpass distortion characteristics with power supply. seen from graphs, distortion with 2.7VP-P output under 0.03% frequencies cutoff frequency 100kHz. stop band attenuation filter greater than 90dB 10MHz. precision specifications over entire rail-to-rail input range have open loop gains million more. These characteristics, combined with voltage operation, makes truly versatile amplifiers.
VIN1
LT1218 VOUT
Multiplexer
buffered with good offset characteristics constructed using shutdown feature LT1218. shutdown, output LT1218 assumes high impedance, outputs devices tied together (wired they digital world). shown Figure shutdown pins each LT1218 driven 74HC04 buffer. LT1218 active with shutdown high. photo Figure shows switching characteristics with 1kHz sine wave applied input other input tied ground. shown, each amplifier connected unity gain, either amplifier both could configured gain.
VIN2
LT1218
INPUT SELECT 74HC04
R2R_08.eps
Figure Amplifier
VIN1
Conclusion latest members LTC's family rail-to-rail amplifiers expand versatility rail-to-rail operation micropower high speed applications. devices maintain
VOUT INPUT SELECT
Figure Amplifier Waveforms
AN87-60
Application Note
LT1256 VOLTAGE-CONTROLLED AMPLITUDE LIMITER Frank Amplitude-limiting circuits useful where signal should exceed predetermined maximum amplitude, such when feeding modulator. clipper, which completely removes signal above certain level, useful many applications, there times when desirable lose information. instance, when video signals have amplitude peaks that exceed dynamic range following processing stages, simply clipping peaks maximum level will result loss detail areas where clipping takes place. Often these well illuminated areas primary subject scene. Because these peaks usually correspond highest level luminosity, they referred "highlights." preserve some detail highlights automatically reduce gain (compress) high signal levels. circuit Figure voltage-controlled breakpoint amplifier that used highlight compression. When input signal reaches predetermined level (the breakpoint), amplifier gain reduced. both breakpoint gain signals greater than breakpoint voltage programmable, this circuit useful systems that adapt changing signal levels. Adaptive highlight compression finds video cameras,
2N4957 2N2857 VIDEO LT1256 1.5k
which have very large dynamic range. Although this circuit developed video signals, used adaptively compress signal within 40MHz bandwidth LT1256. LT1256 video fader connected proportional amounts input signal clipped signal provide voltage-controlled variable gain. clipped signal provided discrete circuit consisting three transistors. acts emitter follower until input voltage exceeds voltage base (the breakpoint voltage VBP). When input voltage greater than VBP, clamps emitters transistors plus VBE. emitter follower,
Figure Multiple-Exposure Photograph Single Line Monochrome Video, Showing Four Different Levels Compression
1.5k
VIDEO
LT1256, LT1004-2.5 100k VCONTROL LT1256,
BREAK POINT VOLTAGE
1.5k
LT1363
1.5k
Figure Voltage-Controlled Amplitude Limiter
AN87-61
Application Note
buffers output drops voltage thus level input signal preserved extent allowed matching temperature tracking transistors used. breakpoint voltage base must remain constant when this transistor turning signal will distorted. LT1363 maintains output impedance well beyond video frequencies makes excellent buffer. LT1495/LT1496: 1.5µA RAIL-TO-RAIL AMPS William Jett Introduction Micropower rail-to-rail amplifiers present attractive solution battery-powered other voltage circuitry. current always desirable battery-powered applications, rail-to-rail amplifier allows entire supply range used both inputs output, maximizing system's dynamic range. Circuits that require signal sensing near either supply rail easier implement using rail-to-rail amplifiers. However, until now, amplifier combined precision offset drift specifications with maximum quiescent current 1.5µA. Operating minuscule 1.5µA amplifier, LT1495 dual LT1496 quad rail-to-rail amplifiers consume almost power while delivering precision performance associated with much higher current amplifiers. LT1495/LT1496 feature "Over-The-Top" operation: ability operate normally with inputs above positive supply. devices also feature reverse-battery protection. Applications ability accommodate input output signal that falls within amplifier supply range makes LT1495/ LT1496 very easy use. following applications highlight signal processing currents.
INPUT CURRENT 1N914
Figure multiple-exposure photograph single line monochrome video, showing four different levels compression ranging from fully limited signal unprocessed input signal. breakpoint peak amplitude clearly show effect circuit; normally only video would compressed.
readout taken from 0µA-200µA, analog meter; LT1495 supplies current gain 1000 this application. configured floating I-to-I converter. consumes only when use, there need on/off switch. Resistors current gain. provides ±10% full- scale adjust meter movement. With supply, maximum current meter limited less than 300µA, protecting movement. Diodes resistor protect inputs from faults 200V. Diode currents below normal operation, since maximum voltage across diodes 375µV, LT1495. acts stabilize amplifier, compensating capacitance between inverting input ground. unused amplifier should connected shown minimum supply current. Error terms from amplifier (base currents, offset voltage) less than 0.5% over operating range, accuracy limited analog meter movement.
100pF
LT1495 1.5V LT1495
1.5V
Nanoampere Meter
simple 0nA-200nA meter operating from flashlight cells lithium battery shown Figure
200µA
1495_05.eps
Figure 0nA-200nA Current Meter
AN87-62
Application Note
100k 15nF 15nF
215k
215k 30nF
215k 100nF LT1495
100nF 200k
1kHz. with filters, filter characteristics determined absolute values resistors capacitors, resistors should have tolerance better capacitors tolerance better.
10nF
eIN/150k ZEROS 50Hz 60Hz
Battery-Current Monitor with Over-the-Top Operation
bidirectional current sensor shown Figure takes advantage extended common mode range LT1495 sense currents into battery while operating from supply. During charge cycle, controls current that voltage drop across equal RSENSE. This voltage then amplified charge output ratio During this cycle, amplifier sees negative offset, which keeps discharge output low. During discharge cycle, active operation similar that during charge cycle. Conclusion
100k
80.6k 15nF 15nF
100nF
169k
169k 30nF
169k
100nF LT1495 OUTPUT
200k 10nF
100k
LT1495/96
Figure Order 10Hz Elliptic Lowpass Filter
Order, 10Hz Elliptic Lowpass Filter
Figure shows order, 10Hz elliptic lowpass filter with zeros 50Hz 60Hz. Supply current primarily determined load amplifiers approximately VO/150k (9µA 1V). overall frequency response shown Figure notch depth zeros 50Hz 60Hz nearly 60dB stopband attenuation greater than 40dB
LT1495/LT1496 extends Linear Technology's range rail-to-rail amplifier solutions truly micropower level. combination extremely current precision specifications provides designers with versatile solution battery-operated devices other power systems.
CHARGE
RSENSE
DISCHARGE
GAIN (dB) FREQUENCY (Hz) 1000
1495_07.eps
LT1495
Figure Frequency Response Figure 96's Order Elliptic Lowpass Filter
LT1495
1495_08.eps
2N3904 DISCHARGE
2N3904 CHARGE
SENSE
Figure Battery-Current Monitor
AN87-63
Application Note
SEND CAMERA POWER VIDEO SAME COAX CABLE Frank Because remotely located video surveillance cameras always have ready source power, convenient both power video signal through single coax cable. this inductor present high impedance video impedance difficulty with this method that frequency spectrum monochrome video signal extends down least 30Hz. composite color video spectrum goes even lower, with components 15Hz. This implies rather large inductor. example, 0.4H inductor impedance only 30Hz, which about minimum necessary. Large inductors have large series resistance that wastes power. More importantly, large inductors have significant amount parasitic capacitance stand good chance going into self resonance below 4MHz video bandwidth
4.7µF TANT 1000µF 0.1µF
thus corrupting signal. circuit shown Figure takes different approach problem using active components. circuitry monitor coax cable supplies power system. LT1206 current feedback amplifier, forms gyrator synthetic inductor. gyrator isolates impedance power supply from cable maintaining reasonably high impedance over video bandwidth while, same time, contributing only series resistance. This needs have enough bandwidth video sufficient output drive supply 120mA camera. selected part guaranteed output current 250mA bandwidth 60MHz, making good fit. Because video needs capacitively coupled, there need split supplies; hence single supply used. supply also gives some headroom voltage drop long cable runs.
CAMERA 20µF
LT1086CT-12
1000µF
ZETEX ZTX749
100' RG58/U
LT1363 1000µF
1000µF
VIDEO
4.7µF TANT
1000µF 2.32k
0.1µF
0.1µF 510k 20µF FILM
LT1363
100µF
11.5k
4.7µF
51pF
LT1206CT
R11,
1000µF
DI_VID_01.eps
Figure Circuit Transmits Video Power Same Coax Cable
AN87-64
MONITOR
Application Note
camera LT1086 fixed regulator (U3) supply black white video camera. LT1363 amp, supplies drive fast, high current transistor. turn, modulates video collector input regulator. This point ground because well bypassed required deliver cable. Because regulator camera needs 1.5V dropout voltage, balance 6.5V dropped series resistance cable. output 200µA, 1.2MHz RAIL-TO-RAIL AMPS HAVE OVER-THE-TOP INPUTS Ramchandani Introduction LT1638 Linear Technology's latest general-purpose, power, dual rail-to-rail operational amplifier; LT1639 quad version. circuit topology LT1638 based Linear Technology's popular LT1490/
CHARGER VOLTAGE 1N4001
LT1206 give headroom between supply video. another LT1363 video-speed amp, receives video from cable, supplies some frequency equalization drives cable monitor. Equalization used compensate high frequency roll camera cable. components shown (R16, C11) gave acceptable monochrome video with feet RG58/U cable. LT1491 amps, with substantial improvements speed. LT1638 five times faster than LT1490. Battery Current Monitor battery-current monitor shown Figure demonstrates LT1639's ability operate with inputs above positive rail. this application, conventional amplifier would limited battery voltage between ground, LT1639 handle battery voltages
VBATTERY
LT1639
2N3904
LT1639
LOGIC
LT1639
2N3904
VSUPPLY
LOGIC HIGH (5V) CHARGING LOGIC (0V) DISCHARGING
LT1639
VOUT
IBATTERY
NOTE:
(VOUT) (RS) (RG/RA GAIN
90.9k VOUT GAIN OPEN, GAIN CLOSED, GAIN AMPS
Figure 100. LT1639 Battery Current Monitor-an Over-The-Top Application
AN87-65
Application Note
high 44V. LT1639 shut down removing VCC. With removed, input leakage less then 0.1nA. damage LT1639 will result from inserting battery backward. When battery charging, amplifier senses voltage drop across output amplifier causes drain sufficient current through balance inputs amplifier Likewise, amplifier form closed loop when battery discharging. current DISTORTION RAIL-TO-RAIL AMPS HAVE 0.003% WITH 100kHz SIGNAL Danh Tran Introduction LT1630/LT1632 duals LT1631/LT1633 quads newest members Linear Technology's family railto-rail amps, which provide best combination performance precision over widest range supply voltages. LT1630/LT1631 deliver 30MHz gain-bandwidth product, 10V/µs slew rate 6nV/Hz input-voltage noise. Optimized higher speed applications, LT1632/LT1633 have 45MHz gainbandwidth product, 45V/µs slew rate 12nV/Hz input voltage noise. Applications ability accommodate input output signals that fall within device' supplies makes these amplifiers very easy use. They exhibit very good transient through proportional current This current flows into converted into voltage. Amplifier buffers amplifies voltage across Amplifier compares outputs amplifier amplifier determine polarity current through scale factor VOUT with open 1V/A. With closed scale factor 1V/100mA currents measured.
response drive impedance loads, which makes them suitable high performance applications. following applications demonstrate versatility these amplifiers.
400kHz Order Butterworth Filter Operation
circuit shown Figure makes voltage operation wide bandwidth LT1630 create 400kHz order lowpass filter with supply. amplifiers configured inverting mode lowest distortion output swing rail-to-rail maximum dynamic range. Figure displays frequency response filter. Stopband attenuation greater than 85dB 10MHz. With 2.25VP-P, 100kHz input signal, filter harmonic distortion products less than -87dBc.
2.32k 2.32k 220pF 6.65k
47pF 2.74k 2.74k 5.62k 470pF 22pF
GAIN (dB) VOUT
2.25VP-P 100k FREQUENCY (Hz)
LT1630
VS/2
Figure 101. Single-Supply, 400kHz, Order Butterworth Filter
AN87-66
LT1630
1630/31 TA01
0.1k
1630/31 TA02
Figure 102. Frequency Response Filter Figure
Application Note
40dB Gain, 550kHz Instrumentation Amplifier
instrumentation amplifier with rail-to-rail output swing, operating from supply, constructed with LT1632, shown Figure 103. amplifier nominal gain 100, which adjusted with resistor output level equal input voltage (VIN) between inputs multiplied gain 100.
VOLTAGE GAIN (dB) 1.5V LOWER LIMIT COMMON MODE INPUT VOLTAGE VCML 100k FREQUENCY (Hz)
1562 TA09
Common mode range calculated equations shown with Figure 103. example, common mode range from 0.15V 2.65V output voltage onehalf supply. common mode rejection greater than 110dB 100Hz when trimmed with resistor Figure shows amplifier's cutoff frequency 550kHz.
DIFFERENTIAL INPUT COMMON MODE INPUT
VOUT(DC)
0.1V
UPPER LIMIT COMMON MODE INPUT VOLTAGE VCMH
550kHz VOUT(DC) (+IN (-IN))DC GAIN
VOUT(DC)
2.85V
Figure 103. Single-Supply Instrumentation Amplifier
LT1167: PRECISION, COST, POWER INSTRUMENTATION AMPLIFIER REQUIRES SINGLE GAIN-SET RESISTOR Alexander Strong Introduction LT1167 next-generation instrumentation amplifier designed replace previous generation monolithic instrumentation amps, well discrete, multiple solutions. Instrumentation amplifiers differ from operational amplifiers that they amplify input signals that ground referenced. output instrumentation amplifier referenced external voltage that independent input. Conversely, output voltage amp, nature feedback, referenced differential common mode input voltage.
LT1632
LT1632
Figure 104. Frequency Response Figure 103's Instrumentation Amplifier
Applications
Single-Supply Pressure Monitor
LT1167's supply current, supply voltage operation input bias current (350pA max) allow nicely into battery powered applications. overall power dissipation necessitates using higher impedance bridges. Figure shows LT1167 connected bridge's differential output. picoampere input bias currents will still keep error caused offset current negligible level. LT1112 level shifts LT1167's reference ADC's analog ground pins above ground. This necessary single-supply applications because output cannot swing ground. LT1167's LT1112's combined power dissipation still less than bridge's. This circuit's total supply current just 3mA.
AN87-67
Application Note
LT1167
DIGITAL DATA SERIAL OUTPUT
LTC1286
LT1112
1167_02.eps
Figure 105. Single-Supply Pressure Monitor
Signal Conditioning LT1167 shown Figure changing differential signal into single-ended signal. single-ended signal then filtered with passive order lowpass filter applied LTC1400 12-bit analog-to-digital converter (ADC). LT1167's output stage easily drive ADC's small nominal input capacitance, preserving signal integrity. Figure shows FFTs amplifier/ADC's output. Figures 107a 107b show results operating LT1167 unity gain gain ten, respectively. This results typical SINAD 70.6dB.
10µF 0.047µF 5.6k 0.033µF 0.1µF VREF LT1167 LTC1400 0.1µF
1167 .eps
AMPLITUDE (dB) -100 -120 SUPPLY VOLTAGE 5.5kHz fSAMPLE 400ksps SINAD 70.6dB LT1167 GAIN
FREQUENCY (kHz)
10µF SUPPLY VOLTAGE 3kHz fSAMPLE 400ksps SINAD 70.6dB LT1167 GAIN
1167 .eps
0.1µF
0.1µF AMPLITUDE (dB) SERIAL INTERFACE
-100 -120
DOUT CONV 0.1µF
10µF
FREQUENCY (kHz) 1167 .eps
Figure 107. Operating Gain (B), Figure 106's Circuit Achieves 12-Bit Operation with SINAD 70.6dB
Figure 106. LT1167 Converting Differential Signals SingleEnded Signals; LT1167 Ideal Driving LTC1400
AN87-68
Application Note
Current Source Figure shows simple, accurate, power programmable current source. differential voltage across pins mirrored across voltage across amplified applied across defining output current. 50µA bias current flowing from buffered LT1464 JFET operational amplifier, which increases resolution current source 3pA. Nerve-Impulse Amplifier LT1167's current noise makes ideal monitors that have source impedances. Demonstrating LT1167's ability amplify level signals, circuit Figure takes advantage amplifier's high gain noise operation. This circuit amplifies level nerve impulse signals received from patient pins LT1167. parallel combination gain ten. potential LT1112's creates ground common mode signal. LT1167's high CMRR 110db ensures that desired differential signal amplified unwanted common mode signals attenuated. Since portion signal important, make 0.3Hz highpass filter. signal LT1112's amplified gain R7/R8 parallel combination forms lowpass filter that decreases this gain frequencies above 1kHz.
PATIENT/CIRCUIT PROTECTION/ISOLATION +INPUT LT1112 0.3Hz HIGHPASS
VIN+
LT1167
VIN-
LT1464 49.4k
1167_04.eps
Figure 108. Precision Current Source
ability operate 0.9mA supply current makes LT1167 ideal battery-powered applications. Total supply current this application 1.7mA. Proper safeguards, such isolation, must added this circuit protect patient from possible harm. Conclusion LT1167 instrumentation amplifier delivers best precision, lowest noise, highest fault tolerance, plus ease provided single-resistor gain setting. LT1167 offered 8-pin PDIP packages. uses significantly less board space than discrete designs.
0.47µF
LT1167
OUTPUT 1V/mV
LT1112
15nF
1167_05.eps
PATIENT GROUND
-INPUT
POLE 1kHz
Figure 109. Medical Monitor
AN87-69
LOAD
Application Note
LEVEL SHIFT ALLOWS VIDEO AMPLIFIER SWING GROUND SINGLE SUPPLY Frank current feedback (CFA) video amplifier made single supply still amplify ground-referenced video with addition simple inexpensive level shifter. circuit Figure amplifier cable driver current output video DAC. video composite component must have sync. single positive supply could LT1227. output LT1227 used here swing within 2.5V negative supply with load over commercial temperature range 70°C. Five diodes feedback loop used, conjunction with level shift output ground. video from output LT1227 charges voltage across allows output swing ground even slightly negative. However, level this negative swing will depend video signal will unpredictable. When scene black, there must sync video remain charged. zero-level component video signal with sync will work with this circuit. output will zero, can,
47µF 10µF 77.37 1.46k FILM
diodes will turn off. load will disconnected from output connected through feedback resistor network This causes about 150mVDC appear output, instead that should there. ground-referenced video signal input needs level shifted into input common mode range LT1227 above negative supply). shift input signal process, input video attenuated factor 2.5. correct gain, offset with zero source impedance, would 1.5k. compensate presence made 1.5k minus 1.46k. trade gain error about 1.5%. left 1.5k, gain correct, there offset error 75mV. gain output offset amplifier. noninverting gain five taken compensate attenuation input level shifter cable termination. voltage offset output this circuit rather sensitive function value input resistors. instance, error value will cause offset 30mV output. This addition offset error introduced amp. Precision resistor networks available Technologies,
SOURCE
4.7µF 0.1µF
VIDEO SOURCE USED TESTING
4.7µF FILM
LT1227
1N4148
LOAD
1.5k 38.1 1.5k
*RESISTORS COMBINATION VALUES, SERIES COMBINATION 2.37 PARALLEL COMBINATION 77.3 SERIES COMBINATION 1.3k 1.46k RESISTORS METAL FILM
Figure 110. Amplifier Cable Driver Current-Output Video
AN87-70
Application Note
714-447-2345) with matching specifications 0.1% better. These could used level shifting resistors, although this would make adjustments like made difficult. Fortunately, there always synchronization information associated with video. simple circuit used restore voltage offsets produced resistor mismatch, offset errors input video. Figure shows additional circuitry needed perform this
FIGURE 110, POINT VIDEO HOLD SAMPLE CLAMP PULSE 0.1µF RESTORE LEVEL (ADJUST DESIRED BLANKING LEVEL) 1.40k LTC201A 10µF FILM 6800pF FILM
function. LTC201A analog switch store offset error during blanking. clamp pulse should wider should occur during blanking. conveniently made delaying sync pulse with shots. sync clamped, clamp pulse must start after before sync pulse offset errors will introduced. integrator made with LT1632 adjusts voltage point (see Figure 110) correct offset.
0.1µF
Figure 111. Restore Subcircuit
LT1468: OPERATIONAL AMPLIFIER FAST, 16-BIT SYSTEMS George Feliz I

Data Conversion, Interface Signal Conditioning Products Richard Markel

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