LT®3513 5-output adjustable switching regulator provides power large T

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LT®3513 5-output adjustable switching regulator provides power large T

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LT3513 2MHz High Current 5-Output Regulator TFT-LCD Panels FEATURES
LT®3513 5-output adjustable switching regulator provides power large TFT-LCD panels. 38-pin device generate 3.3V logic supply along with triple output supply required TFT-LCD panel. lower voltage secondary logic supply also generated with addition external driven internal linear regulator. step-down regulator provides voltage output, VLOGIC, with 1.2A current while capable operating from wide input range 4.5V 30V. high power step-up converter, lower power step-up converter inverting converter provide three independent output voltages: AVDD, VOFF required panel. high-side provides delayed turn-on signal handle 30mA. Protection circuitry ensures that disabled four outputs more than below programmed voltage.
Lare registered trademarks Linear Technology Corporation. PanelProtect trademark Linear Technology Corporation. other trademarks property their respective owners.
4.5V Input Voltage Range Four Integrated Switches: 2.2A Buck, 1.5A Boost, 0.25A Boost, 0.25A Inverter (Guaranteed Minimum Current Limit) External Driver Fixed Frequency, Noise Outputs Inductor Current Sense Buck Soft-Start Outputs Externally Programmable Delay Three Integrated Schottky Diodes PGOOD AVDD Output Disconnect PanelProtectCircuitry Disables Upon Fault Thermally Enhanced 38-Lead Package
APPLICATIONS
Automotive TFT-LCD Displays Large TFT-LCD Desktop Monitors Flat Panel Televisions
TYPICAL APPLICATION
VOFF -10V 20mA 2.2F 69.8k 0.47F 60.4k UVLO LDOPWR NFB4 4.7H VLOGIC 0.5A 0.22F SENSE+ SENSE- LT3513 VON_CLK VONSINK 6.8H VLDO 3.3V 0.5A 42.2k 7.5k 2.7nF 4.7k 2.2nF
3513 TA01a
178k
VLOGIC
53.6k 100k
PGOOD RUN-SS1 RUN-SS2 RUN-SS3/4 47nF VON_CLK 232k
AVDD 80mA
Start-Up Waveforms
RUN/SS 2V/DIV VLOGIC 5V/DIV AVDD 10V/DIV VOFF 10V/DIV
BIAS BOOST
15nF
15nF
15nF 20mA
30.1k
20V/DIV 20V/DIV
165k VLOGIC 2.2F
IIN(AVG) 1A/DIV 0.47F 5ms/DIV
3513 TA01b
4.7nF 1.5nF
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LT3513 ABSOLUTE MAXIMUM RATINGS
(Note
CONFIGURATION
VIEW UVLO SENSE+ SENSE- BIAS BOOST LDOPWR NFB4 RUN-SS1 BIAS
VIN, LDOPWR Voltage .32V UVLO Voltage .32V SW2, SW3, Voltage .40V Voltage .40V VON, VONSINK Voltage .40V PGOOD Voltage .40V Voltage .1V, -40V BOOST Voltage .37V BOOST Over SENSE+, SENSE- Voltage .10V VON_CLK Voltage .10V BIAS, Voltage .10V Voltage RUN-SS1, RUN-SS2, RUN-SS3/4 Voltage FB1, FB2, FB3, Voltage NFB4 Voltage .5V, VC1, VC2, VC3, Voltage Junction Temperature (Note 125°C Operating Temperature Range (Note -40°C 125°C Storage Temperature Range. -65°C 125°C
RUN-SS3/4 RUN-SS2 VONSINK VON_CLK PGOOD
PACKAGE 38-LEAD (5mm 7mm) PLASTIC TJMAX 125°C, 34°C/W, 1°C/W EXPOSED (PIN GND, MUST SOLDERED
ORDER INFORMATION
LEAD FREE FINISH LT3513EUHF#PBF LT3513IUHF#PBF TAPE REEL LT3513EUHF#TRPBF LT3513IUHF#TRPBF PART MARKING* 3513 3513 PACKAGE DESCRIPTION 38-Lead (5mm 7mm) Plastic 38-Lead (5mm 7mm) Plastic TEMPERATURE RANGE -40°C 125°C -40°C 125°C
Consult Marketing parts specified with wider operating temperature ranges. *The temperature grade identified label shipping container. more information lead free part marking, http://www.linear.com/leadfree/ more information tape reel specifications,
denotes specifications which apply over full operating temperature range, otherwise specifications 25°C. 12V, BIAS unless otherwise noted.
PARAMETER Minimum Input Voltage Quiescent Current RUN-SS1, RUN-SS2, RUN-SS3/4 Current RUN-SS1, RUN-SS2, RUN-SS3/4 Threshold BIAS Voltage Begin RUN-SS2, RUN-SS3/4 BIAS Current BIAS 3.1V, Switches
ELECTRICAL CHARACTERISTICS
CONDITIONS
2.25 16.5
UNITS
Switching VRUNSS1 RUN-SS1= RUN-SS2 RUN-SS3 RUN-SS4 0.4V
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LT3513 ELECTRICAL CHARACTERISTICS
PARAMETER Threshold Offset Begin Charge Current Source Threshold Power Switch Drop Maximum Current VON_CLK Input Voltage High VON_CLK Input Voltage VONSINK Voltage Master Oscillator Frequency
denotes specifications which apply over full operating temperature range, otherwise specifications 25°C. 12V, BIAS unless otherwise noted.
CONDITIONS (Note Pins 1.5V, 0.35V Pins 1.5V Current 30mA
UNITS
VONSINK Current
1.90 1.80 1.25 1.215 1.205 1.235 0.01 1.255 1.265 0.03 2.12 2.22
Foldback Switching Frequency UVLO Threshold UVLO Hysteresis Current PGOOD Threshold Offset PGOOD Sink Current PGOOD Leakage Switch (2.2A Buck) Voltage
NFB4 UVLO Voltage Rising VUVLO PGOOD Connected Through 100k VPGOOD
mhos
Voltage Line Regulation Bias Current Error Amplifier Voltage Gain Error Amplifier Transconductance Maximum Duty Cycle Switch Current Limit Switch VCESAT Switch Leakage Current Minimum BOOST Voltage Above BOOST Current BOOST Schottky Diode Drop Switch (1.5A BOOST) Voltage
4.5V (Note
1.20 1.19 1.22 0.01
Duty Cycle (Note 1.5A 1.5V, RUN-SS1 1.5A (Note 1.5A 170mA
1.24 1.25 0.03
mhos
Voltage Line Regulation Bias Current Error Amplifier Voltage Gain Error Amplifier Transconductance Switch Current Limit Switch VCESAT Switch Leakage Current BIAS Current Maximum Duty Cycle (SW2)
4.5V (Note (Note ISW2 1.2A 1.5V, RUN-SS1 ISW2 1.2A
1.85
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LT3513 ELECTRICAL CHARACTERISTICS
PARAMETER Switch (250mA BOOST) Voltage
denotes specifications which apply over full operating temperature range, otherwise specifications 25°C. 12V, BIAS unless otherwise noted.
CONDITIONS 1.20 1.19 1.22 0.01
1.24 1.25 0.03
UNITS mhos
Voltage Line Regulation Bias Current Error Amplifier Voltage Gain Error Amplifier Transconductance Switch Current Limit Switch VCESAT Switch Leakage Current BIAS Current Maximum Duty Cycle (SW3) Schottky Diode Drop Switch (250mA Inverter) NFB4 Voltage
4.5V (Note (Note ISW3 0.2A 1.5V, RUN-SS1 ISW3 0.2A
0.25 -1.205 -1.215 -1.180 0.01
0.38
170mA
-1.155 -1.145 0.03
mhos
NFB4 Voltage Line Regulation NFB4 Bias Current Error Amplifier Voltage Gain Error Amplifier Transconductance Switch Current Limit Switch VCESAT Switch Leakage Current BIAS Current Maximum Duty Cycle (SW4) Schottky Diode Drop (D4) Voltage
4.5V (Note (Note ISW4 0.2A NFB4 -1.5V, RUN-SS1 ISW4 0.2A 170mA 0.61 0.25
0.625
0.40
0.63 0.65
Bias Current Base Drive Current LDOPWR Minimum Voltage
(Note 0.5V 3.5V
Note Stresses beyond those listed under Absolute Maximum Ratings cause permanent damage device. Exposure Absolute Maximum Rating condition extended periods affect device reliability lifetime. Note LT3513E guaranteed meet specified performance from 125°C junction temperature. Specifications over -40°C 125°C operating junction temperature range assured design, characterization correlation with statistical process controls. LT3513I guarenteed over full -40°C 125°C operating junction temperature range. Note held until FB1, FB2, NFB4 ramp above threshold offset. Note Current flows FB1, FB3, NFB4 FB5.
Note Current flow FB2. absolute value this test used. Note Current limit guaranteed design and/or correlation static test. Slope compensation reduces current limit higher duty cycles. Note This minimum voltage across boost capacitor needed guarantee full saturation internal power switch. Note This includes overtemperature protection that intended protect device during momentary overload conditions. Junction temperature will exceed maximum operating junction temperature range when overtemperature protection active. Continuous operation above specified maximum operating junction temperature impair device reliability.
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LT3513 TYPICAL PERFORMANCE CHARACTERISTICS
Maximum Output Current VLOGIC 3.3V
CURRENT LIMIT 4.3H IOUT(MAX) 2.4H
3513
25°C, unless otherwise noted.
Current Limit Duty Cycle
CURRENT LIMIT DUTY CYCLE MINIMUM DUTY CYCLE
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Start VLOGIC 3.3V
VIN(MIN) START VIN(MIN)
0.001
0.01 LOAD CURRENT
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BOOST Current
CURRENT LIMIT BOOST CURRENT (mA)
Current Limit
CURRENT LIMIT (mA) AMBIENT TEMPERATURE (°C)
3513
Current Limit
1000 1500 2000 2500 SWITCH CURRENT (mA) 3000
AMBIENT TEMPERATURE (°C)
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Current Limit
CURRENT LIMIT (mA) VCESAT (mV) AMBIENT TEMPERATURE (°C)
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VCESAT
1000 1000 1500 2000 CURRENT (mA) 2500 3000 VCE2SAT (mV)
VCESAT
1200 ISW2 (mA)
1600
2000
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3513
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LT3513 TYPICAL PERFORMANCE CHARACTERISTICS
VCESAT
ISW3 (mA) (mA) LIMIT (mA) VCESAT (mV)
25°C, unless otherwise noted. Current Limit
VCESAT
VCE3SAT (mV)
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Oscillator Frequency
SWITCHING FREQUENCY (kHz) FREQUENCY (MHz) AMBIENT TEMPERATURE (°C)
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Frequency Foldback
2500 1.25
Reference Voltage
REFERENCE VOLTAGE
2000
1.24
1500
1.23
1000
1.22
1.21
1050 1200 (mV)
3513
1.20
TEMPERATURE (°C)
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BIAS Current
BIAS CURRENT (mA) EFFICIENCY
Efficiency, AVDD
EFFICIENCY
Efficiency, VLOGIC
LOAD CURRENT (mA)
3513
ISW2 ISW3 ISW4
TEMPERATURE (°C)
3513
1100 1300 1500 IOUT (mA)
3513
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LT3513 TYPICAL PERFORMANCE CHARACTERISTICS
Current Limit Temperature
BASE CURRENT LIMIT INTERNAL (mA) UVLO AMBIENT TEMPERATURE (°C) 1.27 1.26 1.31 1.30 1.29 1.28 UVLO MINIMUM 1.33 1.32 UVLO START REFERENCE VOLTAGE (mV)
25°C, unless otherwise noted. Reference Voltage FB5,
VUVLO Temperature
AMBIENT TEMPERATURE
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TEMPERATURE (°C)
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FUNCTIONS
(Pin Feedback Pin. resistor this output according VLDO 0.625 R14/R15). Reference designators refer Figure (Pin Control Voltage Compensation Internal Error Amplifier. Connect series from this ground compensate switching regulator RUN-SS3/4 (Pin Run/Soft-Start Pin. This softstart switching regulators Place soft-start capacitor here limit start-up inrush current output voltage ramp rate. When BIAS reaches 2.25V, current source charges capacitor. When voltage this reaches 0.8V, switches turn begin switching. slower start-up larger capacitor. complete shutdown RUN-SS3/4 ground. (Pin Feedback Pin. resistor this according 1.22V R8/R9) 150mV. Reference designators refer Figure RUN-SS2 (Pin Run/Soft-Start Pin. This soft-start switching regulator Place soft-start capacitor here limit start-up inrush current output voltage ramp rate. When BIAS reaches 2.25V, current source charges capacitor. When voltage this reaches 0.8V, switch turns begins switching. slower start-up larger capacitor. complete shutdown RUN-SS2 ground. (Pin Switch Node. collector internal bipolar transistor switching regulator Minimize trace area this keep down. (Pin This switching regulator output emitter output disconnect output capacitor resistor divider here. (Pin This delayed output switching regulator reaches programmed voltage after internal timer times out. Protection circuitry ensures disabled four outputs more than below normal voltage. This output also disabled when VON_CLK high. VONSINK (Pin This open-collector output controlled VON_CLK pin. When VON_CLK low, this draws current when VON_CLK high, this draws current. VON_CLK (Pin 10): This controls output disconnect device open collector VONSINK. When this low, enabled VONSINK high impedance. When this high, disabled VONSINK sinks current ground.
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LT3513 FUNCTIONS
PGOOD (Pin 11): Power Good Comparator Output. This open collector output power good comparator used conjunction with external P-channel MOSFET provide output disconnect AVDD shown Figure When switcher output reaches approximately programmed voltage, PGOOD will pulled ground. This will pull down gate MOSFET, connecting AVDD. 100k pull-up resistor between source gate P-channel MOSFET keeps when switcher output low. (Pin 12): Control Voltage Compensation Internal Error Amplifier. Connect series from this ground compensate switching regulator (Pin 13): Timing Capacitor Pin. This input timer programs time delay from four feedback pins reaching 1.125V turning capacitor value using equation (20A tDELAY)/1.1V. (Pins 33): Ground. (Pins 16): Switch Node. collector internal bipolar transistor switching regulator Minimize trace area this keep down. BIAS (Pins 29): BIAS used improve efficiency when operating higher input voltages. Connecting this output switching regulator forces most internal circuitry draw operating current from VLOGIC rather than VIN. drivers switches supplied BIAS. Switches will function until BIAS reaches approximately 2.7V. Both BIAS pins must tied VLOGIC. (Pin 19): Feedback Pin. resistor divider this AVDD according AVDD 1.22V R5/R6). Reference designators refer Figure (Pin 20): Control Voltage Compensation Internal Error Amplifier. Connect series from this ground compensate switching regulator (Pin 21): Control Voltage Compensation Internal Error Amplifier. Connect series from this ground compensate switching regulator RUN-SS1 (Pin 22): Run/Soft-Start Pin. This soft-start switching regulator Place soft-start capacitor here limit start-up inrush current output voltage ramp rate. When power applied pin, current source charges capacitor. When voltage this reaches 0.8V, switch turns begins switching. slower start-up larger capacitor. complete shutdown RUN-SS1 ground. NFB4 (Pin 23): Negative Feedback Pin. resistor divider this VOFF according VOFF -1.18 R3/R4). Reference designators refer Figure (Pin 24): Internal Schottky Diode Pin. This anode internal Schottky diode with other connected ground. This Schottky diode used generating VOFF output. (Pin 25): Switch Node. collector internal bipolar transistor switching regulator Minimize trace area this keep down. (Note 26): Base Drive. This controls base external transistor. LDOPWR (Pin 27): Input Voltage Driver. This supplies current base. This connected VIN. save power high voltages, alternatively connected AVDD supply. BOOST (Pin 28): BOOST used provide drive voltage higher than switch drive circuit. internal Schottky diode connected between BIAS BOOST. capacitor needs connected between BOOST SW1. SENSE- (Pin Negative Current Sense Input. This (along with SENSE+ pin) used sense inductor current buck switching regulator.
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LT3513 FUNCTIONS
SENSE+ (Pin Positive Current Sense Input. This (along with SENSE- pin) used sense inductor current buck switching regulator. (Pin 32): Feedback Pin. resistor divider this VLOGIC according VLOGIC 1.235V R1/R2). Reference designators refer Figure (Pins 35): Switch Node. pins emitter internal bipolar power transistor switching regulator These points must tied together proper operation. Connect these pins inductor, catch diode boost capacitor. (Pins 37): Input Voltage. This supplies current internal circuitry LT3513. This must locally bypassed with capacitor. UVLO (Pin 38): Undervoltage Lockout. resistor divider connected tied this program minimum input voltage which LT3513 will operate. This compared internal 1.25V reference. When UVLO less than 1.25V, switching regulators allowed operate (the RUN/SS pins still used turn each switching regulator). When this falls below 1.25V, 3.9A will pulled from provide programmable hysteresis UVLO. Exposed (Pin 39): Ground. Exposed package provides both electrical contact ground good thermal contact printed circuit board. Exposed must soldered circuit board proper operation.
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LT3513 BLOCK DIAGRAM
36,37 RUN-SS1 PGOOD
1.235V
SLOPE COMP/ ONE-SHOT
1.1V
SENSE- CURRENT SENSE
1.22V
1.1V
FOLDBACK OSCILLATOR
1.25V UVLO 3.9A
UVLO
RUN-SS3/4 LOCKOUT 1.18V
BIAS BIAS 2.7V FOLDBACK OSCILLATOR DRIVER
RUN-SS2 LOCKOUT
1.22V
BIAS FOLDBACK OSCILLATOR 1.1V DRIVER
14,17,33 VON_CLK
Figure
INTERNAL REGULATOR REFERENCE
LDOPWR
VON_CLK 0.625V MASTER OSCILLATOR 2MHz VON_CLK VONSINK
BIAS BOOST DRIVER SENSE+
BIAS
DRIVER
100k 100k NFB4
3513
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LT3513 OPERATION
LT3513 highly integrated power supply containing four separate switching regulators dropout linear regulator (LDO). Switching regulator stepdown 2.2A regulator with inductor current sense integrated boost Schottky diode. Switching regulator configured step-up SEPIC converter 1.5A switch. Switching regulator consists step-up regulator with 0.25A switch well integrated Schottky diode. Switching regulator negative regulator with switch current limit 0.25A integrated Schottky diode. Linear regulator capable providing current base external transistor. regulators share common circuitry including input source, voltage reference master oscillator. Operation best understood referring Block Diagram shown Figure RUN-SS1 pulled ground, LT3513 shut down draws from input source tied VIN. internal current source charges external softstart capacitor, generating voltage ramp this pin. RUN-SS1 exceeds 0.8V, internal bias circuits turn including internal regulator, reference 2MHz master oscillator. master oscillator generates four clock signals, each switching regulators. Switching regulator will only begin operate when RUN-SS1 reaches 0.8V. Switcher generates VLOGIC, which must tied BIAS pin. When BIAS reaches 2.8V, NPNs pulling down RUN-SS2 RUN-SS3/4 pins turns off, allowing internal current source charge external capacitors tied RUN-SS2 RUN-SS3/4 pins. When voltage RUN-SS2 reaches 0.8V, switcher enabled. Correspondingly, when voltage RUN-SS3/4 reaches 0.8V, switchers enabled. AVDD, VOFF will then begin rising rate determined capacitors tied RUN-SS2 RUN-SS3/4 pins. When four switching outputs reach their programmed voltages, pulling down will turn off, internal current source will charge external capacitor tied pin. When reaches 1.1V, output disconnect turns connecting event four outputs dropping below their programmed voltage, PanelProtect circuitry pulls GND, disabling VON. power good comparator monitors AVDD turns when above regulated value. output open-collector transistor that when output regulation, allowing external resistor pull high. This used with P-channel MOSFET that functions output disconnect AVDD. four switchers current mode regulators. Instead directly modulating duty cycle power switch, feedback loop controls peak current switch during each cycle. Compared voltage mode control, current mode control improves loop dynamics provides cycle-by-cycle current limit.
RUN-SS 2V/DIV VLOGIC 5V/DIV 1A/DIV SS-234 2V/DIV
AVDD 10V/DIV 500A/DIV PGOOD 20V/DIV
5ms/DIV
3513 F02a
(2a)
VSS3/4 2V/DIV VOFF 10V/DIV
500mA/DIV 20V/DIV 500mA/DIV
2V/DIV 20V/DIV 5ms/DIV
3513 F02b
(2b) Figure LT3513 Power-Up Sequence. (Traces from Both Photos Synchnonized Same Trigger)
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LT3513 OPERATION
four switchers employ constant-frequency current mode control scheme. Switcher step-down regulator, differs slightly from others with inductor current sense. Instead monitoring current switch, current nodes used measure current through inductor. Inductor current sense does suffer from minimum on-time problems, therefore always keeping switch current limited with input-to-output voltage ratio. Switcher always synchronized master oscillator. other three switchers each have their slave oscillator. slave oscillator reduces frequency when feedback voltage dips below 0.75V decreases linearly below threshold shown Performance Characteristics' Frequency Foldback plot. Other than these differences, control loop similar four switchers. pulse from master oscillator switcher pulse from slave oscillator other three switchers sets latch turns internal bipolar power switch. Current switch external inductor begins increase. When this current exceeds level determined voltage current comparator resets latch, turning switch. current inductor flows through Schottky diode begins decrease. cycle begins again next pulse from oscillator. this way, voltage controls current through inductor output. internal error amplifier regulates output continually adjusting voltage. threshold switching 0.8V, active clamp 1.8V limits voltage. Switchers also contain independent current limit dependent duty cycle. Switcher current limit controlled voltage varies with duty cycle. four switchers also slope compensation ensure stability with current mode scheme duty cycles above 50%. RUN-SS1, RUN-SS2 RUN-SS3/4 pins control rate rise feedback pins. switch driver operates either from from BOOST pin. external capacitor integrated Schottky diode used generate voltage BOOST that higher than input supply. This allows driver saturate internal bipolar power switch efficient operation. INPUT VOLTAGE RANGE STEP-DOWN CONSIDERATION minimum operating voltage switcher determined either LT3513's undervoltage lockout maximum duty cycle. user defined undervoltage lockout with UVLO voltage higher than internal undervoltage lockout. duty cycle fraction time that internal switch determined input output voltages: VOUT
where forward voltage drop catch diode (~0.4V) voltage drop internal switch (~0.3V maximum load). This leads minimum input voltage VIN(MIN) VOUT DCMAX
with DCMAX 0.75. user defined undervoltage resistor divider connected UVLO pin. comparator pulls from when UVLO higher than 1.25V. hysteresis minimum input voltage equations follows: VHYS 3.9µA VIN(MIN) 1.25V
UVLO
3513
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LT3513 OPERATION
INDUCTOR SELECTION MAXIMUM OUTPUT CURRENT good first choice inductor value VOUT inductance required avoid subharmonic oscillations, Application Note current inductor triangle wave with average value equal load current. peak switch current equal output current plus half peak-to-peak inductor ripple current. LT3513 limits switch current order protect itself system from overload faults. Therefore, maximum output current that LT3513 will deliver depends switch current limit, inductor value, input output voltages. When switch off, potential across inductor output voltage plus catch diode drop. This gives peak-to-peak ripple current inductor:
where voltage drop catch diode (~0.4V) inductor's current rating must greater than maximum load current saturation current should least higher. highest efficiency, series resistance (DCR) should less than 0.1. Table lists several vendors types that suitable.
Table Inductor Vendors
VENDOR Coilcraft Murata Toko www.coilcraft.com www.murata.com www.component.tdk.com www.toko.com PART SERIES MSS7341 LQH55D SLF7045 SLF10145 DC62CB D63CB D75C D75F CR54 CDRH74 CDRH6D38 CR75 TYPE Shielded Open Shielded Shielded Shielded Shielded Shielded Open Open Shielded Shielded Open
DC)( VOUT
where switching frequency LT3513 value inductor. peak inductor switch current ISW(PK) =ILPK =IOUT
Sumida
www.sumida.com
optimum inductor given application differ from indicated this simple design guide. larger value inductor provides higher maximum load current, reduces output voltage ripple. your load lower than maximum load current, then relax value inductor operate with higher ripple current. This allows physically smaller inductor with lower resulting higher efficiency. aware that maximum load current depends input voltage. graph Typical Performance Characteristics section this data sheet shows maximum load current function input voltage inductor value VOUT 3.3V. addition, inductance result discontinuous mode operation, which further reduces maximum load current. details maximum output current discontinuous mode operation, Linear Technology's Application Note Finally, duty cycles greater than (VOUT/VIN 0.5), minimum
maintain output regulation, this peak current must less than LT3513's switch current limit ILIM. SW1, ILIM least 0.35, decreases linearly 1.5A 0.75 shown Typical Performance Characteristics section. maximum output current function chosen inductor value: IOUT(MAX) =ILIM 2.5A 0.57
Choosing inductor value that ripple current small will allow maximum output current near switch current limit. approach choosing inductor start with simple rule given above, look available inductors choose meet cost space goals. Then these equations check that LT3513 will able deliver required output current. Note again that these equations assume that inductor current continuous. Discontinuous operation occurs when IOUT less than IL/2.
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LT3513 OPERATION
OUTPUT CAPACITOR SELECTION 3.3V outputs, 6.3V ceramic capacitor (X5R X7R) output results very output voltage ripple good transient response. Other types values will also work; following discussion explores tradeoffs output ripple transient performance. output capacitor filters inductor current generate output with voltage ripple. also stores energy order satisfy transient loads stabilizes LT3513's control loop. Because LT3513 operates high frequency, minimal output capacitance necessary. addition, control loop operates well with without presence output capacitor series resistance (ESR). Ceramic capacitors, which achieve very output ripple small circuit size, therefore option. estimate output ripple with following equations: VRIPPLE ceramic capacitors, COUT value capacitors poor dielectrics with high temperature voltage coefficients. particular, types lose large fraction their capacitance with applied voltage temperature extremes. Because loop stability transient response depend value COUT, this loss unacceptable. types. Electrolytic capacitors also option. ESRs most aluminum electrolytic capacitors large deliver output ripple. Tantalum newer, lower organic electrolytic capacitors intended power supply suitable, manufacturers will specify ESR. Chose capacitor with enough required output ripple. Because volume capacitor determines ESR, both size value will larger than ceramic capacitor that would give similar ripple performance. benefit that larger capacitance give better transient response large changes load current. Table lists several capacitor vendors.
Table Surface Mount Capacitors
VENDOR Taiyo Yuden Kemet TYPE Ceramic Ceramic Tantalum Tantalum Organic Organic Organic Organic Ceramic SERIES X5R, X5R, T491, T494, T495 T520 A700 POSCAP X5R,
VRIPPLE electrolytic capacitors (tantalum aluminum) where peak-to-peak ripple current inductor. content this ripple very current rating output capacitor usually concern. estimated with formula: IC(RMS)
Sanyo Panasonic
Another constraint output capacitor that must have greater energy storage than inductor; stored energy inductor transfers output, resulting voltage step should small compared regulation voltage. overshoot, this requirement indicates: COUT VOUT
DIODE SELECTION catch diode from Figure conducts current only during switch-off time. Average forward current normal operation calculated from: ID(AVG) =IOUT VOUT
small size ceramic capacitors make them preferred type LT3513 applications. However, ceramic capacitors same. Many higher
only reason consider diode with larger current rating than necessary nominal operation worst-case condition shorted output. diode current will then increase typical peak switch current. Peak reverse voltage equal regulator input voltage.
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LT3513 OPERATION
diode with reverse voltage rating greater than input voltage. Table lists several Schottky diodes their manufacturers.
Table Schottky Diodes
PART NUMBER Semiconductor MBRM120E MBRM140 MBRS240 MBRA340 Diodes Inc. B120 B240 B340A
-VOUT
1.25 should less avoid bias current errors.
IAVE
VFAT (mV)
(mV)
Regulating Negative Output Voltages LT3513 contains inverting with gain NFB4 works just other pins. Choose resistors according
VOUT 1.25
should 2.5k less avoid bias current errors.
BOOST CONSIDERATIONS minimum operating voltage LT3513 application limited undervoltage lockout maximum duty cycle. boost circuit also limits minimum input voltage proper start-up. input voltage ramps slowly LT3513 turns when output already regulation, boost capacitor fully charged. Because boost capacitor charges with energy stored inductor, circuit will rely some minimum load current boost circuit running properly. This minimum load will depend input output voltages. Typical Performance Characteristics section shows plot minimum load current start function input voltage 3.3V output. minimum load current generally goes zero once circuit started. Even without output load current, many cases discharged output capacitor will present load switcher that will allow start. INVERTER/STEP-UP CONSIDERATIONS Regulating Positive Output Voltages output voltage programmed with resistor divider between output pin. Choose resistors according
NFB4
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Duty Cycle Range maximum duty cycle (DC) LT3513 switching regulator SW2, SW4. duty cycle given application using step-up charge pump topology VOUT VOUT
duty cycle given application using inverter SEPIC VOUT VOUT
LT3513 still used applications where duty cycle, calculated above, greater than maximum. However, part must operated discontinuous mode that actual duty cycle reduced.
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LT3513 OPERATION
Inductor Selection Table lists several inductor vendors types that suitable with LT3513. Consult each manufacturer detailed information their entire selection related parts. ferrite core inductors obtain best efficiency, core losses frequencies above 1MHz much lower ferrite cores than powdered-iron units. inductor will best choice most LT3513 step-up charge pump designs. Choose inductor that carry entire switch current without saturating. inverting SEPIC regulators, coupled inductor, separate inductors option. When using coupled inductors, choose that handle least switch current without saturating. using uncoupled inductors, each inductor need only handle approximately one-half total switch current. 4.7H coupled inductor uncoupled inductors will usually best choice most LT3513 inverting SEPIC designs. Output Capacitor Selection (equivalent series resistance) capacitors output minimize output ripple voltage. Multilayer ceramic capacitors excellent choice, they have extremely available very small packages. dielectrics preferred, followed X5R, these materials retain their capacitance over wide voltage temperature ranges. output capacitor sufficient most LT3513 applications. Even less capacitance required outputs with |VOUT| |IOUT| 100mA. Solid tantalum OS-CON capacitors will also work, they will occupy more board area will have higher than ceramic capacitor. Always capacitor with sufficient voltage rating. Diode Selection Schottky diode recommended with LT3513 switcher switcher Schottky diode switcher integrated inside LT3513. Choose diodes switcher switcher rated handle average current greater than load current rated handle maximum diode voltage. average diode current step-up SEPIC equal load current. Each diodes charge pump configurations carries average diode current equal load current. ground connected diode charge pump integrated into LT3513. maximum diode voltage stepup charge pump configurations equal |VOUT|. maximum diode voltage SEPIC inverting configurations |VOUT|. Input Capacitor Selection Bypass input LT3513 circuit with 4.7F higher ceramic capacitor type. lower value less expensive type will work there additional bypassing provided bulk electrolytic capacitors input source impedance low. following paragraphs describe input capacitor considerations more detail. Step-down regulators draw current from input supply pulses with very fast rise fall times. input capacitor required reduce resulting voltage ripple LT3513 input force this switching current into tight local loop, minimizing EMI. input capacitor must have impedance switching frequency this effectively must have adequate ripple current rating. input capacitor current calculated from step-down output voltage current, input voltage: CIN(RMS) =IOUT VOUT VOUT IOUT
largest when 2VOUT (50% duty cycle). ripple current contribution from other channels will minimal. Considering that maximum load current from switcher ~3A, ripple current will always less than 1.5A. high frequency LT3513 reduces energy storage requirements input capacitor, that capacitance required less than com. bination small size impedance (low equivalent series resistance ESR) ceramic capacitors makes
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LT3513 OPERATION
them preferred choice. results very voltage ripple. Ceramic capacitors handle larger magnitudes ripple current than other capacitor types same value. types. alternative high value ceramic capacitor lower value along with larger electrolytic capacitor, example ceramic capacitor parallel with tantalum capacitor. electrolytic capacitor, value larger than will required meet ripple current requirements. Because input capacitor likely high surge currents when input source applied, only consider tantalum capacitor appropriate surge current rating. manufacturer also recommend operation below rated voltage capacitor. sure place ceramic close possible pins optimal noise immunity. final caution order regarding ceramic capacitors input. ceramic input capacitor combine with stray inductance form resonant tank circuit. power applied quickly (for example plugging circuit into live power source), this tank ring, doubling input voltage damaging LT3513. solution either clamp input voltage dampen tank circuit adding lossy capacitor electrolytic) parallel with ceramic capacitor. details, Application Note Soft-Start Shutdown RUN-SS1(Run/Soft-Start) used place switching regulators internal bias circuits shutdown mode. also provides soft-start function, along with RUN-SS2 RUN-SS3/4. RUN-SS1 pulled ground, LT3513 enters shutdown mode with regulators quiescent current reduced ~30A. internal current source pulls RUN-SS1, RUN-SS2, RUN-SS3/4 pins. RUN-SS1 reaches ~0.6V, internal bias circuits start quiescent currents increase their nominal levels. capacitor tied from RUN-SS1, RUN-SS2 RUN-SS3/4 pins ground, then internal pull-up current will generate voltage ramp these pins. This voltage clamps pin, limiting peak switch current therefore input current during start-up. RUN-SS1 clamps VC1, RUN-SS2 clamps RUN-SS3/4 clamps pins. good value soft-start capacitors COUT/10,000, where COUT value largest output capacitor. Considerations delayed output switching regulator When reaches 1.1V, output disconnect turns connecting current limited will protect LT3513 input source from shorted output. output also controlled from VON_CLK pin. When VON_CLK low, output will turn greater than 1.1V. When VON_CLK high, greater than 1.5V, output disabled VONSINK open collector device turns VONSINK connected through resistor, voltage will decay with high VON_CLK. VON_CLK synced horizontal scanning frequency improve image quality. Voltage Dropout Linear Regulator LT3513 features output drive external transistor provide lower voltage logic supply voltage. output capable providing 10mA current base NPN. output controlled pin. Choose resistor values according 0.625V should less avoid bias current errors. internal compensation relies ceramic capacitor between values 2.2F dielectrics preferred, followed X5R, these materials retain their capacitance over wide voltage temperature ranges.
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LT3513 OPERATION
Printed Circuit Board Layout proper operation minimum EMI, care must taken during printed circuit board (PCB) layout. Figure shows high current paths step-down regulator circuit. Note that step-down regulators, large, switched currents flow power switch, catch diode input capacitor. step-up regulators, large, switched currents flow through power switch, switching diode output capacitor. SEPIC inverting regulators, switched currents flow through power switch, switching diode tank capacitor. loop formed components switched current path should small possible. Place these components, along with inductor output capacitor, same side circuit board, connect them that layer. Place local, unbroken ground plane below these components, this ground plane system ground location, ideally ground terminal
output capacitor Additionally, keep BOOST nodes small possible. Thermal Considerations must provide heat sinking keep LT3513 cool. Exposed bottom package must soldered ground plane. This ground should tied other copper layers below with thermal vias; these layers will spread heat dissipated LT3513. Place additional vias near catch diodes. Adding more copper bottom layers tying this copper internal planes with vias reduce thermal resistance further. With these steps, thermal resistance from junction) ambient reduced 25°C less. With 100LFPM airflow, this resistance fall another 25%. Further increases airflow will lead lower thermal resistance.
(3a)
(3b)
Figure Topside Layout (3c)
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Figure Subtracting Current When Switch (3a) from Current When Switch (3b) Reveals Path High Frequency Switching Current (3c) Keep this Loop Small. Voltage BOOST Nodes Will Also Switched; Keep These Nodes Small Possible. Finally, Make Sure Circuit Shielded with Local Ground Plane
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LT3513 PACKAGE Package 38-Lead Plastic (5mm 7mm)
(Reference 05-08-1701
0.70
0.05
5.50
0.05 4.10 0.05 3.00
5.15 0.05
3.15 0.05
PACKAGE OUTLINE 0.25 0.05 0.50 6.10 7.50 0.05 0.05
RECOMMENDED SOLDER LAYOUT APPLY SOLDER MASK AREAS THAT SOLDERED NOTCH 0.30 0.35 CHAMFER 0.40 0.10 MARK (SEE NOTE
5.00
0.10
0.75
0.05 0.00 0.05
3.00
5.15 0.10 7.00 0.10 5.50
3.15 0.10
(UH) 1107
0.200 0.25
0.05
0.50
0.125
0.10
BOTTOM VIEW-EXPOSED
NOTE: DRAWING CONFORMS JEDEC PACKAGE OUTLINE M0-220 VARIATION WHKD DRAWING SCALE DIMENSIONS MILLIMETERS
DIMENSIONS EXPOSED BOTTOM PACKAGE INCLUDE MOLD FLASH. MOLD FLASH, PRESENT, SHALL EXCEED 0.20mm SIDE EXPOSED SHALL SOLDER PLATED SHADED AREA ONLY REFERENCE LOCATION BOTTOM PACKAGE
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Information furnished Linear Technology Corporation believed accurate reliable. However, responsibility assumed use. Linear Technology Corporation makes representation that interconnection circuits described herein will infringe existing patent rights.
LT3513 RELATED PARTS
PART NUMBER LT3003 LT3465/LT3465A LT3466/LT3466-1 LT3474 LT3475 LT3476 LT3478/LT3478-1 LT3486 LT3491 LT3494/LT3494A LT3497 LT3498 LT3591 DESCRIPTION 3-Channel Ballaster with Dimming Constant Current, 1.2MHz/2.7MHz, High Efficiency White Boost Regulators with Integrated Schottky Diode Dual Constant Current, 2MHz High Efficiency White Boost Regulators with Integrated Schottky Diode 36V, (ILED), 2MHz Step-Down Driver Dual 1.5A (ILED), 36V, 2MHz Step-Down Driver Quad Output 1.5A, 2MHz High Current Driver with 1,000:1 Dimming 42V, 4.5A (ISW), 2.25MHz, Drivers with 3,000:1 True Color Dimming Dual 1.3A, 2MHz High Current Driver Constant Current, 2.3MHz, High Efficiency White Boost Regulator with Integrated Schottky Diode 40V, 180mA/350mA Micropower Noise Boost Converters with Output Disconnect Dual 2.3MHz, Full Function Driver with Integrated Schottkys 250:1 True Color Dimming 2.3MHz, 20mA Driver OLED Driver with Integrated Schottkys COMMENTS VIN: 48V, 3,000:1 True Color PWMTM, MSOP10 Package VIN: 2.7V 16V, VOUT(MAX) 34V, 1.9mA, ThinSOTPackage VIN: 2.7V 24V, VOUT(MAX) 40V, 5mA, 16A, DFN10 Package VIN: 36V, VOUT(MAX) 13.5V, 400:1 True Color PWM, 16A, TSSOP16E Package VIN: 36V, VOUT(MAX) 13.5V, 3,000:1 True Color PWM, TSSOP20E Package VIN: 2.8V 16V, VOUT(MAX) 36V, 1,000:1 True Color PWM, 10A, QFN10 Package VIN: 2.8V 36V, VOUT(MAX) 42V, 6.1mA, TSSOP16E Package VIN: 2.5V 24V, VOUT(MAX) 36V, 1,000:1 True Color PWM, DFN, TSSOP16E Packages VIN: 2.5V 12V, VOUT(MAX) 27V, 2.6mA, DFN6, SC70 Packages VIN: 2.3V 16V, VOUT(MAX) 40V, 65A, DFN8 Package VIN: 2.5V 10V, VOUT(MAX) 32V, 6mA, 12A, DFN10 Package VIN: 2.5V 12V, VOUT(MAX) 32V, 1.65mA, DFN12 Package
Constant Current, 1MHz, High Efficiency White Boost VIN: 2.5V 12V, VOUT(MAX) 40V, 4mA, DFN8 Package Regulator with Integrated Schottky Diode 80:1 True Color Dimming 16-Channel 48V, 2MHz Buck Mode Driver with 3000:1 True Color Dimming VIN: 4.5V 50V, 3,000:1 True Color PWM, QFN56 Package
LT3595
True Color ThinSOT trademarks Linear Technology Corporation.
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Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
0309 PRINTED
1630 McCarthy Blvd., Milpitas, 95035-7417
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2008

LT®3513 5-output adjustable switching regulator provides power large T

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