LT3755 LINER [Linear Technology], LT3755 Datasheet
LT3755
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LT3755 Summary of contents
Page 1
... A frequency adjust pin allows the user to program the frequency from 100kHz to 1MHz to optimize effi ciency, performance or external component size. The LT3755/LT3755-1 sense output current at the high side of the LED string. High side current sensing is the most fl exible scheme for driving LEDs, allowing boost, buck mode or buck-boost mode confi ...
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... LT3755EUD-1#TRPBF LT3755IUD-1#PBF LT3755IUD-1#TRPBF LT3755EMSE#PBF LT3755EMSE#TRPBF LT3755IMSE#PBF LT3755IMSE#TRPBF LT3755EMSE-1#PBF LT3755EMSE-1#TRPBF LT3755IMSE-1#PBF LT3755IMSE-1#TRPBF Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi label on the shipping container. Consult LTC Marketing for information on non-standard lead based fi nish parts. ...
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... ISP PWM = 0V (Standby 48V ISP V – 100mV ISP ISN 1V < V < PWM = ISP ISN ISP ISN Current Out of Pin OPENLED Falling (LT3755 Only) PWMOUT Falling R = 100k 10k T LT3755/LT3755-1 MIN TYP MAX UNITS 4.5 V 0.1 1 μA 5 μA 1.4 1 1.965 2 ...
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... C = 3300pF L Note 2: The LT3755E and LT3755E-1 are guaranteed to meet performance specifi cations from 0°C to 125°C junction temperature. Specifi cations over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3755I and LT3755I-1 are guaranteed to meet performance specifi ...
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... Switching Frequency vs Temperature 1400 R = 10k T 1300 1200 1100 1000 900 800 700 600 100 – –25 TEMPERATURE (°C) LT3755/LT3755 25°C, unless otherwise noted – V Threshold ISP ISN vs Temperature 103 CTRL 102 101 100 –50 ...
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... LT3755/LT3755-1 TYPICAL PERFORMANCE CHARACTERISTICS Quiescent Current 2.0 PWM = 0V 1.5 1.0 0 (V) IN 37551 G10 INTV Voltage (V) IN 37551 G13 SENSE Current Limit Threshold vs Duty Cycle 110 105 100 DUTY CYCLE (%) ...
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... PWM (Pin 8/Pin 2): A signal low turns off switcher, idles oscillator and disconnects VC pin from all internal loads. PWMOUT pin follows PWM pin. PWM has an internal pull-down resistor. If not used, connect to INTV OPENLED (Pin 9/Pin 3, LT3755 Only): An open-drain = 100mV/R when LED pull-down on OPENLED asserts if the FB input is greater ) ...
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... LT3755/LT3755-1 PIN FUNCTIONS (MSOP/QFN) SYNC (Pin 9/Pin 3, LT3755-1 Only): The SYNC pin is used to synchronize the internal oscillator to an external logic level signal. The R resistor should be chosen to program T an internal switching frequency 20% slower than the SYNC pulse frequency. Gate turn-on occurs a fi xed delay after the rising edge of SYNC ...
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... SSCLAMP 50k 50KHz TO 1MHz OSCILLATOR FAULT 10μA + LOGIC 1.25V + – FREQ TSD PROG SS LT3755/LT3755-1 PWM V IN LDO – 1.25V A8 + INTV 7V CC GATE R Q DRIVER S I SENSE SENSE + A4 – GND RAMP OPENLED – 1.2V OPTION FOR + FB LT3755 OPTION FOR RT SYNC LT3755-1 37551 BD 37551fa 9 ...
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... LED current loop entirely, the ISP and ISN should be tied together and the CTRL input tied to V Two LED specifi c functions featured on the LT3755 are controlled by the voltage feedback pin. First, when the FB pin exceeds a voltage 50mV lower (–4%) than the FB regulation voltage, the pull-down driver on the OPENLED pin is activated ...
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... Place the capacitor close to the IC to minimize the trace length to the INTV pin and also to the IC ground internal current limit on the INTV the LT3755 from excessive on-chip power dissipation. The minimum value of this current should be considered when choosing the switching NMOS and the operating frequency. I ...
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... Dimming Control There are two methods to control the current source for dimming using the LT3755. One method uses the CTRL pin to adjust the current regulated in the LEDs. A second method uses the PWM pin to modulate the current source ...
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... When calculating the operating limits, the typical values for on/off-time in the datasheet should be increased by 300 C 250 200 150 100 50 0 –50 100 37551 F04 Figure 5. Typical Minimum On and Off T Pulse Width vs Temperature LT3755/LT3755-1 Value (1% Resistors (kΩ 28.7 53.6 100 = 3300pF GATE MINIMUM ON-TIME MINIMUM OFF-TIME –25 0 ...
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... PWM control latitude, GATE rise/fall times and SW node rise/fall times. Thermal Considerations The LT3755 and LT3755-1 are rated to a maximum input voltage of 40V. Careful attention must be paid to the internal power dissipation of the IC at higher input voltages to en- sure that a junction temperature of 125° ...
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... V of switch on-resistance, R cause switching losses dominate power loss. The INTV regulator on the LT3755 has a fi xed current limit to protect the IC from excessive power dissipation at high V FET should be chosen so that the product of Q switching frequency does not exceed the INTV limit ...
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... SENSE,BOOST V • I LED LED 16 The placement of R the NMOS FET and GND of the LT3755. The SENSE input WEB to LT3755 should be a Kelvin connection to the positive www.vishay.com terminal of R www.fairchildsemi.com www.irf.com Inductor Selection The inductor used with the LT3755 should have a saturation ...
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... GND should be minimized. The ground points of these two switching current traces should come to a common point then connect to the ground plane under the LT3755. Likewise, the ground terminal of the bypass capacitor for the INTV the GND of the switching path. Typically this requirement ...
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... I L1 2A/DIV I LED 500mA/DIV 37551 TA02b 50μs/DIV 18 50W White LED Headlamp Driver L1 22μ SHDN/UVLO FB V ISP 187k REF 16.9k LT3755 CTRL ISN 100k CC NTC M1 GATE RT1 100k SENSE OPENLED 0.015Ω PWM SS RT PWMOUT 0.01μF V GND INTV ...
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... PWM 1k OPENLED SS RT GATE V GND INTV SENSE C CC 28.7k 47k C2 400kHz 4.7μF 0.001μF 100 37551 TA03b 80 15 LT3755/LT3755 249k 14V 4.7μF – 0.068Ω 1.4A 100k Q1 22. LUXEON K2 - WHITE L1 33μ 4.7μF 0.033Ω 37551 TA03a Effi ciency vs V ...
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... PWM Dimming at 100Hz I LED 500mA/DIV PWM 10μs/DIV 20 Buck Mode 1.5A LED Driver with PWM Dimming C1 1μF 510k V ISP IN SHDN/UVLO V ISN REF CTRL PWMOUT Q1 LT3755 PWM 1k OPENLED SS GATE SENSE RT INTV V GND 28.7k 400kHz 15k 4.7μF 2200pF 37551 TA06b 0.068Ω ...
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... ISP 100k ISN OPENLED SS V GND RT C 28.7K 4.7k 0.01μF 400KHz 4700pF 10k Buck-Boost Mode LED Current vs Input Voltage 37551 TA07b LT3755/LT3755-1 0.1k M2 100V 21.5V 2.2μ 1. 100k Q2 PWM 1k 37551 TA07a M1: VISHAY SILICONIX SI7850DP M2: VISHAY SILICONIX SI2319DS Q1: ZETEX FMMT558 Q2: MMBTA42 D1: DIODES INC. PDS560 L1: SUMIDA CDRH127/LD-150 1 ...
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... LT3755/LT3755-1 PACKAGE DESCRIPTION 3.835 0.102 (.151 .004) 5.23 (.206) MIN 0.305 0.038 (.0120 .0015) TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) GAUGE PLANE 0.18 (.007) NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006" ...
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... Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691) 0.70 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC 0.75 ± 0.05 (4 SIDES) 1.45 ± 0.10 (4-SIDES) 0.200 REF 0.00 – 0.05 LT3755/LT3755-1 BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP R = 0.115 OR 0.25 × 45° CHAMFER TYP 15 16 0.40 ± 0. (UD16) QFN 0904 0.25 ± 0.05 ...
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... Buck-Boost LED Driver for Automotive 4.7μF 36V x2 LTC4440-5 INTV V BOOST CC CC GND TG TS INP SHDN/UVLO V GATE REF 330k 383k LT3755 SENSE CTRL INTV CC 47k FB 100k ISP OPENLED D2 PWM SS ISN RT PWMOUT 0.01μF V GND INTV C CC 28.7k INTV 400kHz 10k 10k 1% 0.01μ ...