1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763 high-effic

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1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763 high-effic

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19-1698; 7/00
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter
MAX1763 high-efficiency, low-noise, step-up DC-DC converter intended battery-powered wireless applications. This device maintains exceptionally quiescent supply current (110µA) despite high 1MHz operating frequency. Small external components tiny package make this device excellent choice small hand-held applications that require longest possible battery life. MAX1763 uses synchronous-rectified pulsewidth-modulation (PWM) boost topology generate 2.5V 5.5V outputs from wide range input sources, such three alkaline NiCd/NiMH cells single Lithium-ion (Li+) cell. Maxim's proprietary Idle Modecircuitry significantly improves efficiency light load currents while smoothly transitioning fixed-frequency operation higher load currents maintain excellent full-load efficiency. Lownoise, forced-PWM mode available applications that require constant-frequency operation load currents. MAX1763 also synchronized external clock protect sensitive frequency bands communications equipment. MAX1763 includes on-chip linear gain block that used build high-power external linear regulator low-battery comparator. Soft-start current limit functions permit optimization efficiency, external component size, output voltage ripple. MAX1763 available space-saving 16-pin QSOP package high-power (1.5W) 16-pin TSSOPEP package. Efficiency +0.7V +5.5V Input Voltage Range 1.1V Guaranteed Startup Input Voltage 1.5A Output Fixed 3.3V Output Adjustable (2.5V 5.5V) 1MHz Synchronous-Rectified Topology Logic-Controlled Shutdown Analog Gain Block Linear Regulator LowBattery Comparator Adjustable Current Limit Soft-Start 1.5W TSSOP Package Available
Features
MAX1763
_Applications
Digital Cordless Phones Phones Wireless Handsets Hand-Held Instruments Palmtop Computers Personal Communicators
Ordering Information
PART MAX1763EEE MAX1763EUE TEMP. RANGE -40°C +85°C -40°C +85°C PIN-PACKAGE QSOP TSSOP-EP*
Typical Operating Circuit
0.7V 5.5V 1.5µH
Exposed Idle Mode trademark Maxim Integrated Products.
Configuration
3.3V 1.5A
VIEW
ISET POUT
POUT NORMAL GAIN BLOCK INPUT MAX1763 CLK/SEL ISET PGND
GAIN BLOCK OUTPUT
MAX1763
POUT PGND PGND CLK/SEL
QSOP TSSOP-EP
Maxim Integrated Products
price, delivery, place orders, please contact Maxim Distribution 1-888-629-4642, visit Maxim's website www.maxim-ic.com.
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763
ABSOLUTE MAXIMUM RATINGS
ONA, ONB, GND.0.3V, PGND GND.±0.3V PGND .-0.3V (VPOUT 0.3V) CLK/SEL, REF, ISET, POUT, GND.-0.3V (VOUT 0.3V) POUT .±0.3V Continuous Power Dissipation 16-Pin QSOP (derate 8.7mW/°C above +70°C).667mW 16-Pin TSSOP-EP (derate 19mW/°C above +70°C) .1.5W Operating Temperature Range .-40°C +85°C Junction Temperature .+150°C Storage Temperature Range .-65°C +150°C Lead Temperature (soldering, 10s) .+300°C
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(CLK/SEL PGND GND, ISET REF, POUT, VONA VAIN VOUT 3.6V, +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER DC-DC CONVERTER Input Voltage Range (Note Minimum Startup Voltage (Note Temperature Coefficient Startup Voltage Frequency Startup Mode Internal Oscillator Frequency Oscillator Maximum Duty Cycle (Note External Clock Frequency Range Output Voltage Regulation Voltage Input Current Load Regulation Output Voltage Adjust Range Output Voltage Lockout Threshold (Note ISET Input Leakage Current Supply Current Shutdown No-Load Supply Current, LowPower Mode (Note No-Load Supply Current, LowNoise Mode Gain Block Supply Current Rising edge VISET 1.25V 3.6V, VONA CLK/SEL GND, CLK/SEL VAIN (VOUT 1.4V), gain block enabled 0.1V, CLK/SEL OUT, includes load regulation 1.1A Adjustable output, CLK/SEL OUT, includes load regulation 1.1A 1.35V CLK/SEL OUT, 1.1A 2.00 2.15 0.01 ILOAD 1mA, +25°C ILOAD VOUT 1.5V CLK/SEL 3.17 1.215 1.245 0.01 -1.0 2.30 1000 3.38 1.270 mV/°C CONDITIONS UNITS
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued)
(CLK/SEL PGND GND, ISET REF, POUT, VONA VAIN VOUT 3.6V, +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER DC-DC SWITCHES POUT Leakage Current Leakage Current Switch On-Resistance N-Channel Current Limit P-Channel Turn-Off Current REFERENCE Reference Output Voltage Reference Load Regulation Reference Supply Rejection GAIN BLOCK Reference Voltage Input Current Transconductance Output Voltage Output High Leakage Gain Block Enable Threshold (VOUT VAIN) (Note Gain Block Disable Threshold (VOUT VAIN) (Note LOGIC INPUTS CLK/SEL Input Level CLK/SEL Input High Level Input Level (Note Input High Level (Note Input Leakage Current Minimum CLK/SEL Pulse Width Maximum CLK/SEL Rise/Fall Time 2.5V VOUT 5.5V 2.5V VOUT 5.5V 1.1V VOUT 1.8V 1.8V VOUT 5.5V 1.1V VOUT 1.8V 1.8V VOUT 5.5V CLK/SEL, ONA, VOUT 0.2V 0.01 (0.8) VOUT (0.2) VOUT 20µA VAIN 1.5V 10µA 100µA VAIN 0.5V, 100µA VAIN 1.5V, 5.5V ±0.01 0.01 IREF -1µA IREF 50µA 2.5V VOUT 1.230 1.250 1.270 CLK/SEL VOUT 5.5V VOUT 5.5V, VONA N-channel P-channel 0.075 0.13 0.13 0.25 CONDITIONS UNITS
MAX1763
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763
ELECTRICAL CHARACTERISTICS
(CLK/SEL PGND GND, ISET REF, POUT, VONA VAIN VOUT 3.6V, -40°C +85°C, unless otherwise noted.) (Note
PARAMETER DC-DC CONVERTER Input Voltage Range (Note Minimum Startup Voltage (Note Frequency Startup Mode Internal Oscillator Frequency Oscillator Maximum Duty Cycle (Note External Clock Frequency Range Output Voltage Regulation Voltage Input Current Output Voltage Adjust Range Output Voltage Lockout Threshold (Note ISET Input Leakage Current Supply Current Shutdown No-Load Supply Current, LowPower Mode (Note Gain Block Supply Current DC-DC SWITCHES POUT Leakage Current Leakage Current Switch On-Resistance N-Channel Current Limit P-Channel Turn-Off Current REFERENCE Reference Output Voltage Reference Load Regulation Reference Supply Rejection GAIN BLOCK Reference Voltage Input Current Transconductance Output Voltage Output High Leakage 20µA VAIN 1.5V 10µA 100µA VAIN 0.5V, 100µA VAIN 1.5V, 5.5V IREF -1µA IREF 50µA 2.5V VOUT 1.220 1.270 CLK/SEL VOUT 5.5V VOUT 5.5V, VONA N-channel P-channel 0.13 0.25 Rising edge VISET 1.25V 3.6V, VONA CLK/SEL GND, VAIN (VOUT 1.4V), gain block enabled 0.1V, CLK/SEL OUT, includes load regulation 1.1A Adjustable output, CLK/SEL OUT, includes load regulation 1.1A 1.35V 2.00 ILOAD 1mA, +25°C VOUT 1.5V CLK/SEL 0.75 3.17 1.215 1000 1.25 3.38 1.270 2.30 CONDITIONS UNITS
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued)
(CLK/SEL PGND GND, ISET REF, POUT, VONA VAIN VOUT 3.6V, -40°C +85°C, unless otherwise noted.) (Note
PARAMETER LOGIC INPUTS Gain Block Enable Threshold (VOUT VAIN) (Note Gain Block Disable Threshold (VOUT VAIN) (Note CLK/SEL Input Level CLK/SEL Input High Level Input Level (Note Input High Level (Note Input Leakage Current 2.5V VOUT 5.5V 2.5V VOUT 5.5V 1.1V VOUT 1.8V 1.8V VOUT 5.5V 1.1V VOUT 1.8V 1.8V VOUT 5.5V CLK/SEL, ONA, VOUT 0.2V (0.8) VOUT (0.2) VOUT CONDITIONS UNITS
MAX1763
Note Operating voltage. Because regulator bootstrapped output, once started, MAX1763 will operate down 0.7V input. Note Startup tested with circuit Figure Note Defines low-noise mode maximum step-up ratio. Note regulator startup mode until this voltage reached. apply full load current until output exceeds 2.3V. Note Supply current from 3.3V output measured between 3.3V output pin. This current correlates directly actual battery-supply current, reduced value according step-up ratio efficiency. gain block disabled. Note Connect disable gain block. Note have hysteresis approximately 0.15 VOUT. Note Specifications -40°C guaranteed design production tested.
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763
Typical Operating Characteristics
(Circuit Figure +3.6V, VOUT +5V, +25°C, unless otherwise noted.)
EFFICIENCY OUTPUT CURRENT (VOUT 3.3V)
MAX1763 toc01
EFFICIENCY OUTPUT CURRENT (VOUT
MAX1763 toc02
MAXIMUM OUTPUT CURRENT INPUT VOLTAGE
MAX1763 toc03
EFFICIENCY 0.001 0.01 2.4V 1.2V 0.9V NORMAL MODE FPWM MODE
EFFICIENCY 3.6V 2.4V 1.2V NORMAL MODE FPWM MODE 0.001 0.01
OUTPUT CURRENT VOUT VOUT 3.3V
INPUT VOLTAGE
OUTPUT CURRENT
OUTPUT CURRENT
NO-LOAD INPUT INPUT VOLTAGE
INPUT VOLTAGE INCREASING INPUT VOLTAGE DECREASING
MAX1763 toc04
SHUTDOWN CURRENT INPUT VOLTAGE
1.20 1.15 SHUTDOWN CURRENT (µA) 1.10 FREQUENCY (MHz) 1.05 1.00 0.95 0.90 0.85
INTERNAL OSCILLATOR FREQUENCY TEMPERATURE
MAX1763 toc06
INPUT CURRENT
0.01
3.6V, VOUT 2.4V, VOUT 3.3V
0.001
0.0001 INPUT VOLTAGE
INPUT VOLTAGE
0.80 TEMPERATURE (°C)
STARTUP VOLTAGE OUTPUT CURRENT
MAX1763 toc07
PEAK INDUCTOR CURRENT VISET
MAX1763 toc08
HEAVY-LOAD SWITCHING WAVEFORMS
MAX1763 toc09
STARTUP VOLTAGE 0.001
PEAK INDUCTOR CURRENT
0.01
OUTPUT CURRENT
ISET VOLTAGE
400ns/div 2.4V, VOUT 3.3V, IOUT 1.5A INDUCTOR CURRENT, 500mA/div VLX, 2V/div VOUT, 100mV/div, COUPLED
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter
Typical Operating Characteristics (continued)
(Circuit Figure +3.6V, VOUT +5V, +25°C, unless otherwise noted.)
LIGHT-LOAD SWITCHING WAVEFORMS
MAX1763 toc10
MAX1763
LOAD-TRANSIENT RESPONSE
MAX1763 toc11
LINE-TRANSIENT RESPONSE
MAX1763 toc12
200ns/div 1.1V, VOUT 3.3V, IOUT 20mA NODE, 5V/div INDUCTOR CURRENT, 0.1A/div, COUPLED OUTPUT RIPPLE, 0.1V/div, COUPLED
100µs/div 2.4V, VOUT 3.3V, IOUT 0.2A 1.35A IOUT, 0.5A/div VOUT, 100mV/div, COUPLED
40µs/div 2.4V 1.4V, IOUT 70mA VIN, 1V/div VOUT, 5mV/div, COUPLED
POWER-ON DELAY
MAX1763 toc13
STARTUP WAVEFORMS SOFT-START
MAX1763 toc14
5V/div
VOUT 2V/div
VOUT 2V/div
1A/div
0.5A/div 100µs/div
10mA
5V/div 2ms/div 1.2V, VOUT 3.3V, RLOAD
STARTUP WAVEFORMS USING SOFT-START
MAX1763 toc15
NOISE SPECTRUM
2.4V VOUT 3.3V
MAX1763 toc16
VOUT 2V/div
NOISE (mVRMS)
1A/div
5V/div 2ms/div 1.2V, VOUT 3.3V, 510k, 0.1µF, RLOAD
0.01
FREQUENCY (MHz)
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763
Description
NAME FUNCTION Control Input. When high low, turns Connect normal operation (Table N-Channel Current Limit Control. maximum current limit, connect REF. reduce current, supply voltage between means resistive voltage-divider. soft-start desired, connect capacitor from ISET GND. When high, VREF nominal value, on-chip switched resistor (100k typ) discharges this GND. 1.250V Voltage Reference Bypass Pin. Connect 0.22µF ceramic bypass capacitor GND. 50µA external load current allowed. Ground. Connect PGND with short trace. DC-DC Converter Feedback Input. fixed output voltage +3.3V, connect ground. adjustable output 2.5V 5.5V, connect resistive divider placed from GND. point 1.245V (Figure Power, Supplied from Output. Bypass with 1.0µF ceramic capacitor, connect POUT with series resistor (Figure Gain-Block Input. nominal transconductance from 10mS. external P-channel pass device used build linear regulator. gain block also used low-battery comparator with threshold 0.938V. gain block associated quiescent current disabled connecting OUT. Gain-Block Output. This open-drain N-channel output sinks current when VAIN (0.75)(VREF). high-Z when device shut down, when OUT. Clock Input DC-DC Converter. Also serves program operating mode switcher follows: CLK/SEL Normal; operates fixed frequency, automatically switching low-power mode load minimized. CLK/SEL Forced mode; operates low-noise, constant-frequency mode loads. CLK/SEL Clocked: Forced mode with internal oscillator synchronized 500kHz 1200kHz range. Source N-Channel Power MOSFET Switch. Connect both PGND pins together close device. Inductor Connection. Connect pins together close device. Power Output. P-channel synchronous rectifier source. Control Input. When high low, off. Connect normal operation (Table
ISET
CLK/SEL
PGND POUT
Detailed Description
MAX1763 highly efficient, low-noise power supply portable hand-held instruments. combines boost switching regulator, N-channel power MOSFET, P-channel synchronous rectifier, precision reference, shutdown control, versatile gain block (Figure DC-DC converter boosts one-cell three-cell battery voltage input fixed 3.3V adjustable volt8
between 2.5V 5.5V. external Schottky diode required output voltages greater than MAX1763 guarantees startup with input voltage 1.1V remains operational down input just 0.7V. optimized cellular phones other applications requiring noise quiescent current maximum battery life. features constant-frequency (1MHz), low-noise operation with 1.5A output capability. input allows frequency synchronization control output
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763
UNDERVOLTAGE LOCKOUT POWER 2.15V STARTUP OSCILLATOR CONTROLLER CLK/SEL ISET GAIN BLOCK 0.938V DUAL MODE/ 1.25V REFERENCE 1MHz OSCILLATOR MODE ISET PGND POUT
MAX1763
Figure Functional Diagram
Table Typical Available Output Current
NUMBER CELLS NiCd/NiMH NiCd/NiMH NiCd/NiMH (min) (min) 1300 1100 1600
ISET 0.22µF PGND
0.7V 5.5V
INPUT VOLTAGE
OUTPUT VOLTAGE
OUTPUT CURRENT (mA) 1500
CLK/SEL
1.5µH MBR0520L POUT 1.0µF 3.3V 100µF
47µF
MAX1763
noise spectrum. Table typical available output current. normal mode operation (CLK/SEL low), MAX1763 offers fixed-frequency operation through most load range. light loads (less than full load), device automatically optimizes efficiency switching only needed supply load. Shutdown reduces quiescent current just 1µA. Figure shows standard application circuit MAX1763. external Schottky diode needed output voltage greater than assist low-voltage startup.)
NOTE: HEAVY LINES INDICATE HIGH-CURRENT PATHS.
Figure PFM/PWM Automode Connection
Additional features include synchronous rectification high efficiency increased battery life, gain block that used build linear regulator using external P-channel MOSFET pass device. This gain
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763
Table Selecting Operating Mode
CLK/SEL MODE Normal operation FEATURES High efficiency loads. Fixed frequency light loads. noise, fixed frequency loads. noise, fixed frequency loads.
tered. Noise Spectrum plot Typical Operating Characteristics.
Synchronized-PWM Operation
variation forced-PWM mode, MAX1763 synchronized external frequency applying clock signal CLK/SEL. This allows user choose operating frequency (from 500kHz 1.2MHz) avoid interference sensitive applications. most noise-sensitive applications, limit external synchronization signal duty cycle less than greater than 90%. This eliminates possibility that noise from power switching will coincide with synchronization signal. synchronization signal edge falls power switching edge, slight frequency jitter occur.
External clock 500kHz 1.2MHz
Forced Synchronized
block also function voltage-monitoring comparator. MAX1763 available 16-pin QSOP package 1.5W 16-pin TSSOP-EP package hightemperature high-dissipation applications.
Synchronous Rectifier
MAX1763 features internal 130m P-channel synchronous rectifier enhance efficiency. Synchronous rectification provides efficiency improvement over similar boost regulators that rely diode rectifiers. mode, synchronous rectifier turned during second half each switching cycle. low-power mode, internal comparator turns synchronous rectifier when voltage exceeds boost regulator output turns when inductor current drops below 120mA. When setting output voltages greater than external 0.5A Schottky diode must connected parallel with on-chip synchronous rectifier.
Step-Up Converter
During DC-DC converter operation, internal N-channel MOSFET switch turns first part each cycle, allowing current ramp inductor store energy magnetic field. During second part each cycle, MOSFET turns inductor current flows through synchronous rectifier output filter capacitor load. energy stored inductor depleted, current ramps down synchronous rectifier turns off, Nchannel turns cycle repeats. light loads, depending CLK/SEL setting, output voltage regulated using either switching only needed service load (Table
Low-Voltage Startup Oscillator
MAX1763 uses CMOS low-voltage startup oscillator 1.1V guaranteed minimum startup input voltage. startup, low-voltage oscillator switches N-channel MOSFET until output voltage reaches 2.15V. Above this level, normal feedback control circuitry take over. Once device regulation, operate down 0.7V input because internal power derived from output through pin. apply full system load until output exceeds 2.3V.
Normal Operation
Pulling CLK/SEL selects MAX1763's normal operating mode. this mode, device operates when driving medium heavy loads, light loads only, switches needed. This optimizes efficiency over widest range load conditions. normal operation mode, output voltage regulates higher than forced-PWM mode. Efficiency Load Current Typical Operating Characteristics section.
Shutdown, ONA,
turn MAX1763 off. When device When device (Table Logic high control implemented connecting high using control input. Momentary onepushbutton ON/OFF control described Applications Information section. Both have approximately (0.15 VOUT)V hysteresis.
Forced-PWM Operation
When CLK/SEL high, MAX1763 operates lownoise forced-PWM mode. During forced-PWM operation, MAX1763 switches constant frequency (1MHz) modulates MOSFET switch pulse width control power transferred cycle regulate output voltage. Switching harmonics generated fixed-frequency operation consistent easily fil-
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763
Table On/Off Logic Control
VOUT
100k ISET 0.22µF PGND
MAX1763
CLK/SEL
2.5V 1.5µH 47µF COUT 47µF
3.3V MBRO520L 220µF
POUT 150k MAX1763 POWER-OK OUTPUT
POUT
MAX1763
165k
Figure Using Gain Block Power-OK Comparator
1.8V 5.5V
1.5µH
47µF
BOOST OUTPUT LINEARREGULATED OUTPUT COUT 47µF
Figure Powering Gain Block Linear Regulator from Input Voltage
CLK/SEL
POUT 220µF
Gain Block
MAX1763 gain block function power-OK comparator used build linear regulator using external P-channel MOSFET pass device. gain-block output single-stage transconductance amplifier that drives open-drain N-channel MOSFET. transconductance (GM) entire gain-block stage 10mS. internal gain block amplifies difference between internal 0.938V reference. provide power-OK signal, connect gain-block input, AIN, external resistor-divider (Figure input bias current into less than 30nA, allowing large-value divider resistors without sacrificing accuracy. Connect resistor voltage-divider close possible, within 0.2in (5mm) AIN. Choose value 270k less, then calculate using: R4((VTRIP VAIN where VAIN 0.938V. Figures show gain block used linearregulator application. output external P-channel pass element compared internal 0.938V reference. difference amplified drives gate pass element. logic-level PFET, such Fairchild's NDS336P (RDS(ON) 270m). When
MAX1763
1.0µF
0.22µF
ISET PGND
SIGNAL GROUND POWER GROUND
Figure Using Gain Block Linear Regulator from Boosted Output Voltage
Reference
MAX1763 internal 1.250V reference. Connect 0.22µF ceramic bypass capacitor within 0.2in (5mm) pin. source 50µA external load current.
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter
linear-regulator output voltage regulation, MOSFET will full thus, on-resistance will important. However, linear regulator used dropout, MOSFET on-resistance will determine dropout voltage (VDROPOUT IOUT RDS(ON)). lower RDS(ON) PFET used, increase linear-regulator output filter capacitance maintain stability. output capacitance determined function: COUT (VREF VOUT) COUT (VREF [VOUT GBP]) where VREF 0.983V reference voltage, 10mS internal amplifier transconductance, external MOSFET transconductance, gatesource resistor, gain-bandwidth product internal gain block, 63Mrad/s.
MAX1763
MAX1763
1.245V,
Figure Connecting Resistors External Feedback
0.22µF MAX1763
_Design Procedure
Setting Output Voltage
fixed 3.3V output, connect GND. output voltage between 2.5V 5.5V, connect resistor voltage-divider from (Figure input bias current into less than 100nA, allowing large-value divider resistors without sacrificing accuracy. Connect resistor voltage-divider close possible, within 0.2in (5mm) Choose less, then calculate using: R2((VOUT where VFB, boost-regulator feedback point, 1.245V.
ISET ILIM 2.5A
Figure Soft-Start with Maximum Switch Limit Current
0.22µF RSS1 ISET RSS2 ILIM 2.5A MAX1763
Setting Switch Current Limit Soft-Start
ISET adjusts inductor peak current also used implement soft-start. With ISET connected REF, inductor current limits 2.5A. With ISET connected resistive divider from GND, current limit reduced according ILIM 2.5(VISET 1.25) Implement soft-start placing resistor from ISET (>300k) capacitor from ISET GND. shutdown, ISET discharged through internal 100k resistor. capacitor voltage rises, output current allowed increase, output voltage rises. speed which output rises determined soft-start time constant: where 300k.
RSS2
RSS2
(RSS1 RSS2)CSS
Figure Soft-Start with Reduced Switch Limit Current
Both features implemented simultaneously placing capacitor across lower resistor current-limiting resistive divider (Figures
Package Selection
MAX1763 available packages, 16-pin QSOP 16-pin TSSOP-EP. Since MAX1763 excellent efficiency, most applications well served QSOP package. application requires high power dissipation, operation high ambient temperature, choose TSSOP-EP package.
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763
Table Component Selection Guide
INDUCTORS Coilcraft LPT3305 Sumida CAPACITORS series Kemet T510 series Sanyo POSCAP series Panasonic SP/CB Nihon EP10QY03 Motorola MBR0520L DIODES Coilcraft Kemet Motorola Sumida
Table Component Suppliers
SUPPLIER PHONE USA: 843-448-9411 USA: 847-639-6400 USA: 810-287-2536 USA: 408-629-4789 Japan: 81-45-474-7030 USA: 847-956-0666 Japan: 011-81-3-3667-3302
TSSOP-EP equipped with exposed metal underside soldering grounded circuit board copper. This reduces junction-to-case thermal resistance package from +115°C/W QSOP +53°C/W TSSOP-EP. ambient temperature +70°C, continuous power dissipation QSSOP package 667mW, while TSSOP-EP dissipate 1.5W. first-order estimate power dissipation determined calculating output power delivered load (e.g., 3.3V 3.3W). input voltage used, find efficiency from Typical Operating Characteristics graphs (e.g., 87%). estimated power dissipation MAX1763 then: (100% %Efficiency) Output Power. example would have: 3.3W 0.43W, allowing QSOP package (667mW) used. higher ambient temperature, higher output power, lower-efficiency operating point, TSSOP-EP package (1.5W) necessary. detailed package mechanical information, package outline drawings this data sheet.
Note: Please indicate that using MAX1763 when contacting these component suppliers.
parallel with on-chip synchronous rectifier (Figure diode should rated 0.5A. Representative devices Motorola MBR0520L, Nihon EP05Q03L, generic 1N5817. This external diode also recommended applications that must start with input voltages below 1.8V. Schottky diode carries current during both startup after synchronous rectifier turns off. Thus, current rating only needs 500mA even inductor current higher. Connect diode close possible. ordinary rectifier diodes; their slow switching speeds long reverse-recovery times render them unacceptable. circuits that require startup with inputs below 1.8V, have output less, external diode needed.
Input Output Capacitors
Choose input output capacitors that will service input output peak currents with acceptable voltage ripple. Choose input capacitors with working voltage ratings over maximum input voltage, output capacitors with working voltage ratings higher than output. 220µF, equivalent-series-resistance (ESR) (less than 100m) capacitor recommended most applications. Alternatively, 100µF capacitors parallel will reduce effective even better performance. input capacitor reduces peak currents drawn from input source also reduces input switching noise. input voltage source impedance determines required size input capacitor. When operating directly from NiMH cells placed close MAX1763, single 47µF low-ESR input filter capacitor. With higher impedance batteries, such alkaline Li+, higher value input capacitor improve efficiency. Sanyo POSCAP, Panasonic SP/CB, Kemet T510 good low-ESR capacitors (Tables Low13
Inductor Selection
MAX1763's high switching frequency allows small 1.5µH surface-mount inductor. chosen inductor should generally have saturation current rating exceeding N-channel switch current limit; however, acceptable bias inductor current into saturation much slight reduction efficiency acceptable. Inductors rated lower peak current used ISET employed reduce peak inductor current (see Setting Switch Current Limit Soft-Start). high efficiency, choose inductor with high-frequency ferrite core material reduce core losses. minimize radiated noise, toroid shielded inductor. Table suggested components Table list component suppliers. Connect inductor from battery pins close possible.
External Diode
output voltages greater than external Schottky diode must connected from POUT,
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763
tantalum capacitors offer good trade-off between price performance. exceed ripple current ratings tantalum capacitors. Avoid aluminum electrolytic capacitors; their high typically results higher output ripple voltage. MAX1763 TSSOP-EP package features exposed thermal underside. This lowers package's thermal resistance providing direct thermal heat path from board. Additionally, ground (GND) also channels heat. Connect exposed thermal circuit ground using large multiple vias ground plane.
Bypass Components
ceramic bypass capacitors required proper operation. Bypass with 0.22µF. Also, bypass with ceramic capacitor, connect POUT with resistor. Each these components should placed close their respective pins possible, within 0.2in (5mm). Table lists suggested suppliers.
Step-Up/Step-Down Applications
some battery-powered applications, battery voltage range overlaps output voltage. this case, depending battery voltage, regulator will have step voltage down. make stepup/step-down regulator, gain block make linear regulator that follows step-up converter. this case, battery voltage low, then circuit will step when battery voltage high, linear regulator will drop voltage. Gain Block section gain block make linear regulator. When output voltage greater than regulation voltage, then synchronous rectifier will held reducing dropout, thus increasing efficiency when battery voltage close slightly above, regulation voltage.
Layout Considerations
High switching frequencies large peak currents make board layout critical part design. Poor design will cause excessive ground bounce, both which cause instability regulation errors corrupting voltage current feedback signals. Power components, such inductor, converter filter capacitors, should placed close together possible, their traces should kept short, direct, wide. Keep voltage feedback network very close within 0.2in (5mm) pins. Keep noisy traces, such those from pin, away from voltage feedback networks guarded from them using grounded copper. external rectifier used, traces must kept especially short absolute minimum copper area avoid excess capacitance that slow operation on-chip synchronous rectifier actually reduce efficiency. Refer MAX1763 full board example.
Chip Information
TRANSISTOR COUNT: 1530 SUBSTRATE CONNECTED
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter
Package Information
QSOP.EPS
MAX1763
Note: MAX1763EEE 16-pin QSOP does have heat slug. MAX1763EUE higher power dissipation.
1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763
Package Information (continued)
TSSOP, 4.0,EXP PADS.EPS
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
_Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600 2000 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.

1.5A, Low-Noise, 1MHz, Step-Up DC-DC Converter MAX1763 high-effic

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