LT®3477 current mode, DC/DC step-up converter with dual rail-to-rail c
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LT3477 DC/DC Converter with Dual Rail-to-Rail Current Sense DESCRIPTION
LT®3477 current mode, DC/DC step-up converter with dual rail-to-rail current sense amplifiers internal switch. combines traditional voltage feedback loop unique current feedback loops operate constant-current, constant-voltage source. Both current sense voltages 100mV adjusted independently using IADJ1 IADJ2 pins. Efficiency achieved typical applications. LT3477 features programmable soft-start function limit inductor current during start-up. Both inputs error amplifier available externally allowing positive negative output voltages (boost, inverting, SEPIC, Flyback). switching frequency programmable from 200kHz 3.5MHz through external resistor. Available thermally enhanced 20-pin (4mm 4mm) 20-pin TSSOP packages, LT3477 provides complete solution both constant-voltage constantcurrent applications.
Lare registered trademarks Linear Technology Corporation. other trademarks property their respective owners.
Dual 100mV Rail-to-Rail Current Sense Amplifiers Wide Input Voltage Range: 2.5V Internal Switch High Efficiency Power Conversion: Drives LEDs Boost, Buck-Boost Buck Mode Frequency External Resistor: 200kHz 3.5MHz Programmable Soft-Start VCESAT Switch: 0.3V 2.5A Capable Positive Negative Output Voltages (Boost, Inverting, SEPIC, Flyback) Available Thermally Enhanced 20-Lead (4mm 4mm) 20-Lead TSSOP Packages
APPLICATIONS
High Power Driver Modems Distributed Power Input/Output Current Limited Boost, SEPIC, Inverting, Flyback Converters Constant-Voltage, Constant-Current Source
TYPICAL APPLICATION
330mA Driver With Open Protection
3.3F ISP1 IADJ1 IADJ2 SHDN SHDN LT3477 ISN1 3.3F
Efficiency
200k
EFFICIENCY
ISP2 ISN2
VREF
330mA 33nF
IOUT
3477 TA01b
4.7nF
3477 TA01a
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LT3477 ABSOLUTE MAXIMUM RATINGS
(Note
Voltage VIN, SHDN Voltage FBP, Voltage VREF Voltage. Voltage IADJ1, IADJ2 Voltage ISP1, ISP2, ISN1, ISN2 Voltage .42V
Junction Temperature 125°C Operating Temperature Range (Note LT3477E 40°C 85°C LT3477I -40°C 125°C Storage Temperature Range.- 65°C 125°C Lead Temperature (Soldering, sec) TSSOP 300°C
CONFIGURATION
VIEW SHDN VREF IADJ2 ISN1 ISP1 ISN2 ISP2
VIEW
SHDN ISP1 ISN2 ISP2 IADJ1 IADJ2
IADJ1
PACKAGE 20-LEAD PLASTIC TSSOP
PACKAGE 20-LEAD (4mm 4mm) PLASTIC
TJMAX 125°C, 40°C/W EXPOSED (PIN PGND (MUST SOLDERED PCB)
TJMAX 125°C, 37°C/W EXPOSED (PIN PGND (MUST SOLDERED PCB)
ORDER INFORMATION
LEAD FREE FINISH LT3477EFE#PBF LT3477IFE#PBF LT3477EUF#PBF LT3477IUF#PBF TAPE REEL LT3477EFE#TRPBF LT3477IFE#TRPBF LT3477EUF#TRPBF LT3477IUF#TRPBF 3477 3477 PART MARKING PACKAGE DESCRIPTION 20-Lead Plastic TSSOP 20-Lead Plastic TSSOP 20-Lead (4mm 4mm) Plastic 20-Lead (4mm 4mm) Plastic TEMPERATURE RANGE -40°C 85°C -40°C 125°C -40°C 85°C -40°C 125°C
Consult Marketing parts specified with wider operating temperature ranges. Consult Marketing information non-standard lead based finish parts. more information lead free part marking, http://www.linear.com/leadfree/ more information tape reel specifications,
ELECTRICAL CHARACTERISTICS
PARAMETER Minimum Input Voltage Quiescent Current Reference Voltage Reference Voltage Line Regulation
indicates specifications which apply over full operating temperature range, otherwise specifications 25°C. 2.5V, VSHDN 2.5V.
CONDITIONS
VREF
ISN1
1.250 1.260 0.03
UNITS
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VSHDN VSHDN 2.5V, 0.3V (Not Switching) Grade Grade 2.5V 25V, 0.3V
1.216 1.210
1.235 1.235 0.01
LT3477 ELECTRICAL CHARACTERISTICS
PARAMETER Maximum VREF Current Soft-Start Current Bias Current Bias Current Feedback Amplifier Offset Voltage Feedback Amplifier Voltage Gain Voltage Feedback Amplifier Transconductance Feedback Amplifier Sink Current Feedback Amplifier Source Current Current Sense Amplifier Sense Voltage VFBP 1.25V, VFBN 1.5V, VFBP 1.25V, VFBN 0.5V Positive Rail, 25V, Grade Positive Rail, 25V, Grade Ground 17.2k 107.4k 2.44k 17.2k (Note (Note VSHDN VSHDN
indicates specifications which apply over full operating temperature range, otherwise specifications 25°C. 2.5V, VSHDN 2.5V.
CONDITIONS 0.5V, FBN, 97.5 97.5 102.5 1.15 UNITS
Switching Frequency
Maximum Switch Duty Cycle Switch Current Limit Switch VCESAT Switch Leakage Current SHDN Current SHDN Threshold
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 LT3477E guaranteed meet performance specifications from 70°C. Specifications over 40°C 85°C operating
junction temperature range assured design, characterization correlation with statistical process controls. LT3477I guaranteed over full -40°C 125°C operating junction temperature range. Note Switch current limit switch VCESAT package guaranteed design and/or correlation static test.
TYPICAL PERFORMANCE CHARACTERISTICS
Switch VCE(SAT)
0.50 0.45 0.40 0.35 VCE(SAT) 0.30 0.25 0.20 0.15 0.10 0.05 SWITCH CURRENT
3477
Switch Current Limit
VREF
1.27 1.26 1.25
CURRENT 125°C 25°C
VREF
1.24 1.23
2.5V
-50°C
1.22 1.21
TEMPERATURE (°C)
3477
TEMPERATURE (°C) 3477
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LT3477 TYPICAL PERFORMANCE CHARACTERISTICS
SHDN Turn-On Threshold
SHDN Current
-50°C
Quiescent Current
0.3V
QUIESCENT CURRENT (mA)
SHDN CURRENT
SHDN THRESHOLD
25°C 125°C
TEMPERATURE (°C)
VSHDN
3477
TEMPERATURE (°C)
3477
3477
Soft-Start Current
Oscillator Frequency
OFFSET VOLTAGE (mV)
Feedback Amplifier Offset Voltage
0.5V
FREQUENCY (MHz)
TEMPERATURE (°C)
3477
TEMPERATURE (°C)
3477
TEMPERATURE (°C)
3477
Bias Current
INDICATES CURRENT FLOWS
BIAS CURRENT (nA)
Bias Current
INDICATES CURRENT FLOWS
BIAS CURRENT (nA)
TEMPERATURE (°C)
TEMPERATURE (°C)
3477
3477
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LT3477 TYPICAL PERFORMANCE CHARACTERISTICS
Current Sense Voltage Temperature
CURRENT SENSE VOLTAGE (mV)
Current Sense Voltage IADJ
VOLTAGE SENSE (mV)
TEMPERATURE (°C)
IADJ VOLTAGE (mV)
2477
3477
FUNCTIONS (QFN/TSSOP)
(Pins 20/Pins 20): Connect Pin. Okay connect ground VIN, float. (Pin 3/Pin Input Supply. Must locally bypassed. Powers internal control circuitry. (Pin 4/Pin Timing Resistor Pin. Adjusts switching frequency. Connect 17.2k resistor between 1MHz switching frequency. leave this open. Table additional values switching frequencies. SHDN (Pin 5/Pin Shutdown. greater enable device. below 0.3V turn device. (Pin 6/Pin Soft-Start. Place soft-start capacitor here. Leave floating use. (Pin 7/Pin Compensation Error Amplifier. Connect series from this GND. Typical values 4.7nF. (Pin 8/Pin Inverting Input Error Amplifier. Connect resistive divider here positive output voltage. (Pin 9/Pin Noninverting Input Error Amplifier. Connect resistive divider here negative output voltage. VREF (Pin 10/Pin Bandgap Voltage Reference. Internally 1.235V. Connect this generating positive output external resistor divider generating negative voltage. This provide 100A current locally bypassed with 100pF capacitor. IADJ2 (Pin 11/Pin Second Current Sense Adjustment. Setting IADJ2 less than 625mV leads adjustment sensed voltage second current sense amplifier linearly. IADJ2 tied higher than 650mV, default current sense voltage 100mV. current sense amplifier used, always IADJ2 higher than 650mV. IADJ1 (Pin 12/Pin 10): First Current Sense Adjustment. Setting IADJ1 less than 625mV leads adjustment sensed voltage first current sense amplifier linearly. IADJ1 tied higher than 650mV, default current sense voltage 100mV. current sense amplifier used, always IADJ1 higher than 650mV.
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LT3477 FUNCTIONS
(QFN/TSSOP)
ISP2 (Pin 13/Pin 11): Second Current Sense Pin. noninverting input second current sense amplifier. Connect ISN2 used. ISN2 (Pin 14/Pin 12): Second Current Sense Pin. inverting input second current sense amplifier. Connect ISP2 used. ISP1 (Pin 15/Pin 13): First Current Sense Pin. noninverting input first current sense amplifier. Connect ISN1 used. ISN1 (Pin 16/Pin 14): First Current Sense Pin. inverting input first current sense amplifier. Connect ISP1 used.
(Pins 17/Pin 15): Ground. directly local ground plane. (Pins 19/Pins 17): Switch Pins. Collector internal power switch. Connect inductor diode here minimize metal trace area connected this minimize electromagnetic interference. Exposed (Pin 21/Pin 21): Power Ground. Must soldered ground electrical contact rated thermal performance.
BLOCK DIAGRAM
ISP1
ISN1 IADJ1
VADJ
ISP2
ISN2 IADJ2
VADJ
VREF 1.25V SHDN
VREF
OSCILLATOR
3477
Figure LT3477 Block Diagram
SLOPE
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LT3477 OPERATION
LT3477 uses fixed frequency, current mode control scheme provide excellent line load regulation. Operation best understood referring Block Diagram Figure start each oscillator cycle sets latch turns power switch signal noninverting input comparator SLOPE) proportional switch current oscillator ramp. When SLOPE exceeds (the output feedback amplifier), comparator resets latch turns power switch. this manner, feedback amplifier comparators correct peak current level keep output regulation. Amplifier drives inverting input. three inputs, from voltage feedback loop other from current feedback loop. Whichever feedback input higher takes precedence, forcing converter into either constant-current constant-voltage mode. LT3477 designed transition cleanly between modes operation. Current sense amplifier senses voltage between ISP1 ISN1 pins provides pre-gain amplifier When voltage between ISP1 ISN1 reaches 100mV, output provides VADJ inverting input converter constant-current mode. current sense voltage exceeds 100mV, output will increase causing output decrease, thus reducing amount current delivered output. this manner current sense voltage regulated 100mV. current sense level also adjustable IADJ1. Forcing IADJ1 less than 625mV will overwrite VADJ voltage that's internally, thus providing current level control. second current sense amplifier, IA2, works same first current sense amplifier IA1. Both current sense amplifiers provide rail-to-rail current sense operation. Similarly, positive output voltage operation where tied VREF, increases above VREF, output will decrease reduce peak current level regulate output (constant-voltage mode). negative output voltage operation where tied GND, decreases below level, output will decrease reduce peak current level regulate output (constant-voltage mode). LT3477 also features soft-start function. During start-up, current charges external soft-start capacitor. directly limits rate voltage rise pin, which turn limits peak switch current. switch current constantly monitored allowed exceed nominal value switch current reaches latch reset regardless output comparator. Current limit protects power switch external components.
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LT3477 APPLICATIONS INFORMATION
Capacitor Selection (equivalent series resistance) ceramic capacitors should used output minimize output ripple voltage. only dielectrics, these materials retain their capacitance over wider voltage temperature ranges better than other dielectrics. 4.7F output capacitor sufficient most high output current designs. Converters with lower output currents need only 2.2F output capacitor.
Table Ceramic Capacitor Manufacturers
MANUFACTURER Taiyo Yuden Murata PHONE (408) 573-4150 (803) 448-9411 (714) 852-2001 (847) 803-6100 www.t-yuden.com www.avxcorp.com www.murata.com www.component.tdk.com
percentage nominal value-typically 65%. inductor pass current larger than rated value without damaging Aggressive designs where board space precious will exceed maximum current rating inductor save board space. Consult each manufacturer determine maximum inductor current measured much more current inductor reliably conduct. Diode Selection Schottky diodes, with their forward voltage drop fast switching speed, ideal LT3477 applications. Table lists several Schottky diodes that work well with LT3477. diode's average current rating must exceed average output current. diode's maximum reverse voltage must exceed output voltage. diode conducts current only when power switch turned (typically less than duty cycle), diode sufficient most designs. companies below also offer Schottky diodes with higher voltage current ratings.
Table Suggested Diodes
MANUFACTURER REVERSE PART NUMBER CURRENT VOLTAGE MANUFACTURER UPS340 UPS315 B220 B230 B240 B320 B330 B340 SBM340 Microsemi www.microsemi.com Diodes, www.diodes.com
Inductor Selection Several inductors that work well with LT3477 listed Table However, there many other manufacturers devices that used. Consult each manufacturer more detailed information their entire range parts. Ferrite core inductors should used obtain best efficiency. Choose inductor that handle necessary peak current without saturating, ensure that inductor (copper-wire resistance) minimize power losses. 4.7H inductor will suffice most LT3477 applications. Inductor manufacturers specify maximum current rating current where inductance falls some
Table Suggested Inductors
MANUFACTURER PART NUMBER CDRH6D283R0 CDRH6D28100 CDRH4D284R7 B4R7M B100K LQH55DN4R7M01L LQH55DN100M01K FDV0630-4R7M 1.32 INDUCTANCE (mm) MANUFACTURER Sumida www.sumida.com Taiyo Yuden www.t-yuden.com Murata www.murata.com Toko www.toko.com
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LT3477 APPLICATIONS INFORMATION
Setting Positive Output Voltages positive output voltage, select values (see Figure according following equation: VOUT =1.235V
LT3477 VREF
3477
VOUT
designs needing adjustable current level, IADJ1 IADJ2 pins provided first second current sense amplifiers, respectively. With IADJ1 IADJ2 pins tied higher than 650mV, nominal current sense voltage 100mV (appearing between ISP1 ISN2 ISP2 ISN2 pins). Applying positive voltage less than 600mV IADJ1 IADJ2 pins will decrease current sense voltage according following formula: ISENSE 100mV VIADJ SENSE 618mV
Figure Positive Output Voltage Feedback Connections
Setting Negative Output Voltages negative output voltage, select values (see Figure according following equation: VOUT -1.235V
-VOUT LT3477 VREF
3477
example, 309mV applied IADJ1 RSENSE 0.5, current sense will reduced from 200mA 100mA. adjustability allows regulated current reduced without changing current sense resistor (e.g., adjust brightness driver reduce charge current battery charger). Considerations When Sensing Input Current addition regulating output current current-source applications, constant-current loop LT3477 also used provide accurate input current limit. Boost converters cannot provide output short-circuit protection, surge turn-on current drastically reduced using LT3477 current sense input. SEPICs, however, have output that DCisolated from input, input current limit only helps soft-start output also provides excellent short-circuit protection. When sensing input current, sense resistor should placed front inductor (between decoupling capacitor inductor). This will regulate average inductor current maintain consistent inductor ripple current, which will, turn, maintain well regulated input current. place sense resistor between input source input decoupling capacitor, this allow inductor ripple current vary widely (even though average input current average inductor current will still regulated). Since inductor current triangular waveform (not waveform like output current)
Figure Negative Output Voltage Feedback Connections
Selecting RSENSE/Current Sense Adjustment Using following formula choose correct current sense resistor value (for constant current fail-safe operation). RSENSE 100mV ISENSE
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LT3477 APPLICATIONS INFORMATION
some tweaking compensation values pin) required ensure clean inductor ripple current while constant-current loop effect. these applications, constant-current loop response usually improved reducing value adding capacitor (with value approximately CC/10) parallel with compensation network. Frequency Compensation LT3477 external compensation (VC), which allows loop response optimized each application. external resistor capacitor sometimes just capacitor) placed provide pole zero just pole) ensure proper loop compensation. Several other poles zeroes present closedloop transfer function switching regulator, pole zero positioned provide best loop response. thorough analysis switching regulator control loop within scope this data sheet, will presented here, values 4.7nF will good choice many designs. those wishing optimize compensation, 4.7nF starting point. Board Layout with switching regulators, careful attention must paid board layout component placement. maximize efficiency, switch rise fall times made short possible. prevent radiation high frequency resonance problems, proper layout high frequency switching path essential. Minimize length area traces connected always ground plane under switching regulator minimize interplane coupling. signal path including switch, output diode output capacitor COUT, contains nanosecond rise fall times should kept short possible. Soft-Start many applications, necessary minimize inrush current start-up. built-in soft-start circuit significantly reduces start-up current spike output voltage overshoot. typical value soft-start capacitor 10nF. Switching Frequency switching frequency LT3477 external resistor attached pin. leave this open. resistor must always connected proper operation. Table Figure resistor values corresponding frequencies. Increasing switching frequency reduces output voltage ripple also reduces efficiency. user should frequency maximum tolerable output voltage ripple.
Table Switching Frequency
SWITCHING FREQUENCY (MHz)
SWITCH FREQUENCY (MHz)
2.43 3.65 4.87 6.81 10.2 17.4 43.2
3477
Figure Switch Frequency
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LT3477 APPLICATIONS INFORMATION
Dimming applications where wide dimming range required, competing methods available: analog dimming dimming. easiest method simply vary current through LED-analog dimming-but changing current also changes chromaticity, undesirable many applications. better method dimming, which switches off, using duty cycle control average current. dimming offers several advantages over analog dimming method preferred manufacturers. modulating duty cycle signal, average current changes proportionally illustrated Figure chromaticity LEDs remains unchanged this scheme since current either zero programmed current. Another advantage dimming over analog dimming that wider dimming range possible. LT3477 DC/DC converter that ideally suited applications. LT3477, analog dimming offers dimming ratio about 10:1; whereas, dimming with addition external components results wider dimming range 500:1. technique requires logic signal applied gate both NMOS (refer Figure When signal taken high part runs normal operation ILED 100mV/RSENSE runs
through LEDs. When input taken low, LEDs disconnected turn off. This unique external circuitry produces fast rise time current, resulting wide dimming range 500:1 frequency 100Hz. current controlled feeding signal with broad range frequencies. Dimming below 80Hz possible, desirable, perceptible flashing LEDs lower frequencies. current controlled higher frequencies, dimming range decreases with increasing frequency, seen Figure dimming used boost (shown Figure buck mode (shown Figure buck-boost mode (shown Figure typical boost topology, efficiency exceeds 80%. Buck mode used increase power handling capability higher current applications. buck-boost driver works best applications where input voltage fluctuates higher lower than total voltage drop. high temperature applications, leakage Schottky diode increases, which turn, discharges output capacitor during time. This results smaller effective dimming ratio. Consequently, dimming range decreases about 200:1 85°C.
1000
6.81k
6.81k
CURRENT (mA)
DIMMING RANGE:
BOOST LEDs FREQUENCY 100Hz DUTY CYCLE
3477
0.01
3477
FREQUENCY (kHz)
Figure Current Duty Cycle Wide Dimming Range (500:1)
Figure Dimming Range Frequency
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LT3477 APPLICATIONS INFORMATION
2.0H 3.3F LT3477 VREF ISP2 ISN2 100Hz 100k NMOS1 2.4k 10nF
3477 F07a
ISP1 IADJ1 IADJ2 SHDN
ISN1
33nF
RSENSE 0.33 LED1 6.81k LED2 LED3 LED4 NMOS2 300mA
TAIYO YUDEN EMK316BJ335ML TAIYO YUDEN UDK325BJ106MM TOKO D53LC (PN# A915AY-2ROM) ZETEX ZLLS1000 DIODES 1N4148 NMOS1: ZETEX 2N7002 NMOS2: FAIRCHILD FDG327N LED1 LED4: LUMILEDS LXHL-BW02
Figure White LEDs: Boost With Dimming
EFFICIENCY
CURRENT BOOST LEDs, 300mA FREQUENCY 100Hz DUTY CYCLE
3477 F07c
EFFICIENCY
5V/DIV
1A/DIV
ILED 200mA/DIV
3477 F07b
LEDs 300mA
10s/DIV FREQ 100Hz BOOST
Figure Dimming Waveforms
Figure Efficiency Current Duty Cycle
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LT3477 APPLICATIONS INFORMATION
PVIN 2.2F RSENSE 0.33 LED1
300mA NIPPON NTS40X5R1H225M TAIYO YUDEN GMK316BJ105ML TAIYO YUDEN LMK316BJ335KL TOKO D53LC (PN# A915AY-100M) ZETEX ZLLS400 DIODES 1N4148 NMOS1, NM0S2: ZETEX 2N7002 PMOS: SILICONIX Si2303BDS LED1 LED6: LUMILEDS LXHL-BW02
LED6 NMOS2
PMOS
280k
ISP1 3.3V 3.3F IADJ1 IADJ2 SHDN 33nF
ISN1
LT3477
VREF ISP2 ISN2
100Hz 100k 0.1F NMOS1
3477 F08a
6.81k
Figure White LEDs: Buck Mode With Dimming
5V/DIV
500mA/DIV ILED 500mA/DIV
3477 F08b
2ms/DIV PVIN LEDs 300mA FREQUENCY 100Hz BUCK MODE
Figure Dimming Waveforms
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LT3477 APPLICATIONS INFORMATION
TAIYO YUDEN LMK316BJ335ML TAIYO YUDEN UDK325BJ106MM TOKO D53LC (PN# A915AY-4R7M) ZETEX ZLLS1000 DIODES 1N4148 NMOS1, NMOS2: ZETEX 2N7002 PMOS: SILICONIX Si2303BDS LED1, LED2: LUMILEDS LXHL-BW02 NMOS2 LED2 PMOS 300mA LED1
4.7H
RSENSE 0.33
3.3F
ISP1 IADJ1 IADJ2 SHDN
ISN1
VREF
49.9k
LT3477 33nF 100Hz 100k NMOS1 1.5k 10nF
3477 F09a
ISP2 ISN2 6.81k
Figure White LEDs: Buck-Boost Mode With Dimming
10V/DIV
1A/DIV ILED 500mA/DIV
3477 F09b
LEDs 300mA
2ms/DIV FREQUENCY 100Hz BUCK-BOOST MODE
Figure Dimming Waveforms
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LT3477 TYPICAL APPLICATIONS
5.5V SEPIC Converter With Short-Circuit Protection
0.04 3.3F ISP1 IADJ1 IADJ2 SHDN SHDN LT3477 ISN1 4.7H
Efficiency
0.15
5.5V 670mA 34.8k
EFFICIENCY
4.7H
ISP2 ISN2 33nF 18.2k
3477 TA02a
VREF 4.7nF
IOUT
3477 TA02b
TAIYO YUDEN LMK316BJ335ML TAIYO YUDEN LMK325BJ106MN TAIYO YUDEN LMK316BJ106ZL DIODES INC. DFLS130L TOKO FDV0630-4R7M
800mA, Boost Converter With Accurate Input Current Limit
0.033 2.2F ISP1 IADJ1 IADJ2 SHDN SHDN VREF 4.7nF TAIYO YUDEN LMK316BJ225MD 1206YD106MAT DIODES INC. B320A TOKO FDV0630-4R7M 10nF 17.8k
3477 TA04a
Efficiency
EFFICIENCY
4.7H
0.8A ISP2 23.2k 200k
ISN1
IOUT
LT3477 ISN2
3477 TA04b
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LT3477 TYPICAL APPLICATIONS
Efficient, Driver
0.05 3.3F 200k LT3477 ISP2 ISN2 33nF LED1 LED2 LED3 LED4
3477 TA03a
Efficiency
3.3F
EFFICIENCY
ISP1 IADJ1 IADJ2
ISN1
IOUT
3477 TA01b
330mA
SHDN
SHDN
VREF 4.7nF
TAIYO YUDEN LMK316BJ335ML TAIYO YUDEN TMK325BJ335MN DIODES INC. DFLS120L TOKO A915AY-100M
Buck Mode High Current Driver
PVIN LED1 LED4 2.2F
Efficiency
STRING
EFFICIENCY
280k
CURRENT
3477 TA05b
ISP1 3.3V 3.3F SHDN IADJ1 IADJ2 SHDN
ISN1
LT3477 ISP2 ISN2 33nF
3477 TA05a
4.7nF VREF
NIPPON UNITED CHEMICON NTS40X5R1H225M TAIYO YUDEN GMK316BJ105ML TAIYO YUDEN LMK316BJ475 TOKO A814AY-330M DIODES DFLS140
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LT3477 TYPICAL APPLICATIONS
Buck-Boost Mode Driver
LED2 LED1 4.7H 3.3F 200k
2.7V
ISP1 IADJ1 IADJ2 SHDN
ISN1
BRIGHTNESS CONTROL 650mV SHDN
LT3477
ISP2 ISN2
VREF 10nF TAIYO YUDEN LMK316BJ335ML MURATA GRM31CR71E475KA88L DIODES, INC. B320A TOKO FDV0630-4R7M
33nF
4.7F
3477 TA06a
Efficiency
4.2V IOUT
3477 TA06b
IOUT 0.57 0.74 0.83 0.93
EFFICIENCY
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LT3477 PACKAGE DESCRIPTION
Package 20-Lead Plastic (4mm 4mm)
(Reference 05-08-1710)
0.70 ±0.05 4.50 0.05 3.10 0.05 2.45 0.05 SIDES)
PACKAGE OUTLINE 0.25 ±0.05 0.50 RECOMMENDED SOLDER PITCH DIMENSIONS BOTTOM VIEW-EXPOSED 4.00 0.10 SIDES) MARK (NOTE 2.45 0.10 (4-SIDES) 0.75 0.05 0.115 0.38 0.10 NOTCH 0.30
(UF20) 10-04
0.200 0.00 0.05 NOTE: DRAWING PROPOSED MADE JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGD-1)-TO APPROVED DRAWING SCALE DIMENSIONS MILLIMETERS DIMENSIONS EXPOSED BOTTOM PACKAGE INCLUDE MOLD FLASH. MOLD FLASH, PRESENT, SHALL EXCEED 0.15mm SIDE EXPOSED SHALL SOLDER PLATED SHADED AREA ONLY REFERENCE LOCATION BOTTOM PACKAGE
0.25 0.05 0.50
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LT3477 PACKAGE DESCRIPTION
Package 20-Lead Plastic TSSOP (4.4mm)
(Reference 05-08-1663)
Exposed Variation
3.86 (.152)
6.40 6.60* (.252 .260) 3.86 (.152) 1918
6.60 ±0.10 4.50 ±0.10
NOTE
2.74 (.108) 0.45 ±0.05 1.05 ±0.10 0.65
6.40 2.74 (.252) (.108)
RECOMMENDED SOLDER LAYOUT
1.20 (.047)
4.30 4.50* (.169 .177)
0.25
0.09 0.20 (.0035 .0079)
0.50 0.75 (.020 .030)
0.65 (.0256)
NOTE: CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS DIMENSIONS (INCHES) DRAWING SCALE
0.195 0.30 (.0077 .0118)
0.05 0.15 (.002 .006)
FE20 (CB) TSSOP 0204
RECOMMENDED MINIMUM METAL SIZE EXPOSED ATTACHMENT *DIMENSIONS INCLUDE MOLD FLASH. MOLD FLASH SHALL EXCEED 0.150mm (.006") SIDE
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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.
LT3477 TYPICAL APPLICATION
Buck Mode High Current Driver
PVIN LED1 LED4 2.2F
Efficiency
EFFICIENCY
STRING
280k
ISP1 3.3V 3.3F SHDN IADJ1 IADJ2 SHDN
ISN1
LT3477 ISP2 ISN2 33nF
3477 TA07
CURRENT
3477 TA05b
4.7nF VREF
NIPPON UNITED CHEMICON NTS40X5R1H225M TAIYO YUDEN GMK316BJ105ML TAIYO YUDEN LMK316BJ475 TOKO A814AY-330M DIODES DFLS140
RELATED PARTS
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Constant Current, Constant Voltage 1.4MHz, High Efficiency Boost Regulator
(ISW 800kHz, Step-Up DC/DC Converter VIN: 25V, VOUT(MAX) 34V, 0.9mA, TSSOP16E Package Synchronous Buck-Boost High Power White VIN: 2.7V 5.5V, VOUT(MAX) 5.5V, 2.5mA, QFN16 Package Driver Dual Constant Current, 2MHz, High Efficiency White Boost Regulator With Integrated Schottky Diode Full Featured Boost/Inverter Converter With Soft-Start Single Cell 350mA, 1.3MHz Driver VIN: 2.7V 24V, VOUT(MAX) 40V, 5mA, 16A, Package
LT3479 LTC3490
VIN: 2.5V 24V, VOUT(MAX) 40V, 5mA, DFN/TSSOP Packages VIN: 3.2V, VOUT(MAX) 4.7V, DFN/SO8 Packages
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Linear Technology Corporation
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