LT3755/LT3755-1/LT3755-2 40V , 75V LED Controllers

1 LT3755/LT3755-1/LT3755-2 37551fdTypical applicaTionFeaTuresapplicaTionsDescripTi on40 VIN, 75 VOUT LED ControllersThe LT 3755, LT3755-1 and LT3755-2 are DC/DC control-lers designed to operate as a constant - current source for driving high current LEDs. They drive a low side external N-channel power MOSFET from an internal regulated supply. The fixed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. A ground referenced voltage FB pin serves as the input for several LED protection features, and also makes it possible for the converter to operate as a constant -voltage source. A frequency adjust pin allows the user to program the frequency from 100kHz to 1 MHz to optimize efficiency, performance or external component size. The LT3755/LT3755-1/LT3755-2 sense output current at the high side of the LED string. High side current sensing is the most flexible scheme for driving LEDs, allowing boost, buck mode or buck-boost mode configuration.

2 The PWM input provides LED dimming ratios of up to 3000:1, and the CTRL input provides additional analog dimming capability. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by Patents including 7199560, White Automotive LED Headlamp Drivern 3000:1 True Color PWM Dimmingn Wide Input Voltage Range: to 40Vn Output Voltage Up to 75Vn constant - current and constant -Voltage Regulationn 100mV High Side current Sensen Drives LEDs in Boost, Buck Mode, Buck-Boost Mode, SEPIC or Flyback Topologyn Adjustable Frequency: 100kHz to 1 MHzn Open LED Protectionn Programmable Undervoltage Lockout with Hysteresisn Improved Open LED Status Pin (LT3755-2)n Frequency Synchronization (LT3755-1)n PWM Disconnect Switch Drivern CTRL Pin Provides Analog Dimmingn Low Shutdown current .

3 <1 An Programmable Soft-Startn Thermally Enhanced 16-Lead QFN (3mm 3mm) and MSOP Packagesn High Power LEDn Battery Chargersn Accurate current Limited Voltage RegulatorsVINLT3755-222 FVIN8V F50 WLEDSTRING37551 TA01aOPENLEDPWMSSRTISNGATESENSEPWMOUTE fficiency vs VINVIN (V)01080 EFFICIENCY (%)8488929610020304037551 TA01bLT3755/LT3755-1/LT3755-2 37551fdabsoluTe MaxiMuM raTingsVIN ..40 VSHDN/UVLO (Note 3) ..40 VISP, ISN ..75 VINTVCC .. VIN + , 8 VGATE, PWMOUT (Note 4) .. INTVCC + , PWM, OPENLED ..12 VVC, VREF, SS, FB ..3 VSYNC ..8V(Note 1)orDer inForMaTion161514135678 TOP VIEW17 GNDUD PACKAGE16-LEAD (3mm s 3mm) PLASTIC QFN91011124321 VREFPWMSYNC OR OPENLEDSSFBPWMOUTGATESENSECTRLVCISPISNRTSHDN/UVLOINTVCCVIN TJMAX = 125 C, JA = 68 C/W, JC = C/WEXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB12345678 PWMOUTFBISNISPVCCTRLVREFPWM161514131211109 GATESENSEVININTVCCSHDN/UVLORTSSSYNC OR OPENLEDTOP VIEWMSE PACKAGE16-LEAD PLASTIC MSOP17 GND TJMAX = 125 C (E, I GRADES), TJMAX = 150 C (H GRADE), JA = 43 C/W, JC = 4 C/WEXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCBpin conFiguraTionRT.

4 Junction Temperature Range (Notes 2, 5) LT3755E/LT3755I .. 40 C to 125 C LT3755H .. 40 C TO 150 CStorage Temperature Range .. 65 C to 150 CLead Temperature (Soldering, 10 sec) MSOP .. 300 CLEAD FREE FINISHTAPE AND REELPART MARKING*PACKAGE DESCRIPTIONTEMPERATURE RANGELT3755 EUD#PBFLT3755 EUD#TRPBFLDGC16-Lead (3mm 3mm) Plastic QFN 40 C to 125 CLT3755 IUD#PBFLT3755 IUD#TRPBFLDGC16-Lead (3mm 3mm) Plastic QFN 40 C to 125 CLT3755 EUD-1#PBFLT3755 EUD-1#TRPBFLDMS16-Lead (3mm 3mm) Plastic QFN 40 C to 125 CLT3755 IUD-1#PBFLT3755 IUD-1#TRPBFLDMS16-Lead (3mm 3mm) Plastic QFN 40 C to 125 CLT3755 EUD-2#PBFLT3755 EUD-2#TRPBFLFJZ16-Lead (3mm 3mm) Plastic QFN 40 C to 125 CLT3755 IUD-2#PBFLT3755 IUD-2#TRPBFLFJZ16-Lead (3mm 3mm) Plastic QFN 40 C to 125 CLT3755 EMSE#PBFLT3755 EMSE#TRPBF375516-Lead Plastic MSOP 40 C to 125 CLT3755 IMSE#PBFLT3755 IMSE#TRPBF375516-Lead Plastic MSOP 40 C to 125 CLT3755 EMSE-1#PBFLT3755 EMSE-1#TRPBF3755116-Lead Plastic MSOP 40 C to 125 CLT3755 IMSE-1#PBFLT3755 IMSE-1#TRPBF3755116-Lead Plastic MSOP 40 C to 125 CLT3755 EMSE-2#PBFLT3755 EMSE-2#TRPBF3755216-Lead Plastic MSOP 40 C to 125 CLT3755 IMSE-2#PBFLT3755 IMSE-2#TRPBF3755216-Lead Plastic MSOP 40 C to 125 CLT3755 HMSE-2#PBFLT3755 HMSE-2#TRPBF3755216-Lead Plastic MSOP 40 C to 150 CConsult LTC Marketing for parts specified with wider operating temperature ranges.

5 *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish more information on lead free part marking, go to: For more information on tape and reel specifications, go to: 37551fdelecTrical characTerisTics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C. VIN = 24V, SHDN/UVLO = 24V, CTRL = 2V, PWM = 5V, unless otherwise Minimum Operating VoltageVIN Tied to Shutdown IQSHDN/UVLO = 0V, PWM = 0V SHDN/UVLO = , PWM = 5 A AVIN Operating IQ (Not Switching)PWM = Voltage100 A IVREF 0 Line VIN current Limit Thresholdl98108118mVSENSE Input Bias CurrentCurrent Out of Pin40 ASS Pull-Up CurrentCurrent Out of Pin81013 AError AmplifierISP/ISN Full-Scale current Sense ThresholdFB = 0V, ISP = 48Vl96100103mVISP/ISN Full-Scale current Sense Threshold at CTRL = 0 VCTRL = 0V, FB = 0V, ISP = 48V 12 7mVCTRL Pin Range for current Sense Threshold Input Bias CurrentCurrent Out of Pin50100nALED current Sense Amplifier Input Common Mode Range (VISN) Short-Circuit ThresholdISN = 0V115150200mVISP/ISN Short-Circuit Fault Sensing Common Mode Range (VISN)l03 VISP/ISN Input Bias current (Combined)PWM = 5V (Active), ISP = ISN = 48V PWM = 0V (Standby), ISP = ISN = 48V55 0 A ALED current Sense Amplifier gmV(ISP ISN)

6 = 100mV120 SVC Output Impedance1V < VC < 2V15000k VC Standby Input Bias CurrentPWM = 0V 2020nAFB Regulation Voltage (VFB) ISP = ISN VFB Amplifier gmFB = VFB, ISP = ISN480 SFB Pin Input Bias CurrentCurrent Out of Pin40100nAFB Open LED ThresholdOPENLED Falling (LT3755 and LT3755-2)VFB 65mVVFB 50mVVFB 40mVVFB Overvoltage ThresholdPWMOUT Falling VFB + 50mVVFB + 60mVVFB + 75mVVVC current Mode Gain ( VVC/ VSENSE)4V/VOscillatorSwitching FrequencyRT = 100k RT = 10k l90 925100 1000125 1050kHz kHzMinimum Off-Time170nsLT3755/LT3755-1/LT3755-2 37551fdelecTrical characTerisTics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C. VIN = 24V, SHDN/UVLO = 24V, CTRL = 2V, PWM = 5V, unless otherwise RegulatorINTVCC Regulation (VIN INTVCC)IINTVCC = 10mA, VIN = 7V350mVINTVCC Undervoltage current Limit293440mAINTVCC current in ShutdownSHDN/UVLO = 0V, INTVCC = 7V812 ALogic Inputs/OutputsPWM Input High Input Low Pin Resistance to GND4560 k PWMOUT Output Low (VOL)050mVPWMOUT Output High (VOH)INTVCC Threshold Voltage Falling E-, I-Grades H-Gradel VSHDN/UVLO Rising Hysteresis20mVSHDN/UVLO Input Low VoltageIVIN Drops Below 1 Pin Bias current LowSHDN/UVLO = ASHDN/UVLO Pin Bias current HighSHDN/UVLO = Output Low (VOL)IOPENLED = (LT3755 and LT3755-2)200mVSYNC Pin Resistance to GNDLT3755-1 Only30k SYNC Input HighLT3755-1 Input LowLT3755-1 Drivertr GATE Driver Output Rise TimeCL = 3300pF35nstf GATE Driver Output Fall TimeCL = 3300pF35nsGATE Output Low (VOL) Output High (VOH)INTVCC 1.

7 Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and 2: The LT3755E, LT3755E-1 and LT3755E-2 are guaranteed to meet performance specifications from 0 C to 125 C junction temperature. Specifications over the 40 C to 125 C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3755I, LT3755I-1 and LT3755I-2 are guaranteed to meet performance specifications over the 40 C to 125 C operating junction temperature range. The LT3755H-2 is guaranteed to meet performance specifications over the full 40 C to 150 C operating junction temperature range. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125 3: For VIN below 6V, the SHDN/UVLO pin must not exceed VIN for proper 4: GATE and PWMOUT pins are driven either to GND or INTVCC by internal switches.

8 Do not connect these pins externally to a power 5: The LT3755 includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed the maximum operating junction temperature when overtemperature protection is active. Continuous operating above the specified maximum operating junction temperature may impair device 37551fdTypical per ForMance characTerisTicsFB Regulation Voltage vs Temperature VREF Voltage vs Temperature VREF Voltage vs VIN Switching Frequency vs RTSwitching Frequency vs TemperatureSHDN/UVLO Hysteresis current vs Temperature V(ISP ISN) Threshold vs VCTRL V(ISP ISN) Threshold vs VISPV(ISP ISN) Threshold vs TemperatureRT (k)SWITCHING FREQUENCY (kHz)37551 G071000010001001010100 VCTRL (V)0 20V(ISP ISN) THRESHOLD (mV) G01 ISP VOLTAGE (V)097V(ISP ISN) THRESHOLD (mV)991011039810010237551 G02 VCTRL = 2V2040806097991011039810010237551 G03V(ISP ISN) THRESHOLD (mV)TEMPERATURE ( C) 5005075 2525100150125 VCTRL = 2V37551 G04 VFB (V)TEMPERATURE ( C) 5005075 G05 VREF (V)TEMPERATURE ( C) 5005075 (V) (V) G0637551 G08 SWITCHING FREQUENCY (kHz)TEMPERATURE ( C) 5005075 2525100150125300350400450500RT = G09 TEMPERATURE ( C) 5005075 ( A)

9 = 25 C, unless otherwise 37551fdTypical per ForMance characTerisTics INTVCC Voltage vs VININTVCC current Limit vs Temperature INTVCC Voltage vs Temperature Quiescent current vs VINSENSE current Limit Threshold vs TemperatureSHDN/UVLO Threshold vs TemperatureVIN (V)0 VIN current (mA) G10010204030 PWM = 0V37551 G11 SENSE THRESHOLD (mV)TEMPERATURE ( C)9010011095105 5005075 252510015012537551 G12 SHDN/UVLO VOLTAGE (V)TEMPERATURE ( C) RISINGSHDN/UVLO FALLING 5005075 2525100150125010204030 VIN (V)0 VINTVCC (V)482637551 G1337551 G14 INTVCC current LIMIT (mA)TEMPERATURE ( C)303440323638 5005075 252510015012537551 G15 INTVCC (V)TEMPERATURE ( C) 5005075 = 25 C, unless otherwise current Limit Threshold vs Duty Cycle V(ISP-ISN) Threshold vs FB VoltageGate Rise/Fall Time vs CapacitanceDUTY CYCLE (%)95 SENSE THRESHOLD (mV)10511510011037551 G160255075100FB VOLTAGE (V)37551 (ISP ISN) THRESHOLD (mV)VCTRL = 2 VCAPACITANCE (nF)37551 G180246108040100206080 TIME (ns)GATE RISETIMEGATEFALL TIME10% TO 90% LT3755/LT3755-1/LT3755-2 37551fdpin FuncTionsPWMOUT (Pin 1/Pin 11): Buffered Version of PWM Signal for Driving LED Load Disconnect NMOS or Level Shift.

10 This pin also serves in a protection function for the FB overvoltage condition will toggle if the FB input is greater than the FB regulation voltage (VFB) plus 60mV (typical). The PWMOUT pin is driven from INTVCC. Use of a FET with gate cut-off voltage higher than 1V is (Pin 2/Pin 12): Voltage Loop Feedback Pin. FB is intended for constant -voltage regulation or for LED protec-tion/open LED detection. The internal transconductance amplifier with output VC will regulate FB to (nominal) through the DC/DC converter. If the FB input is regulating the loop, the OPENLED pull-down is asserted. This ac-tion may signal an open LED fault. If FB is driven above the FB threshold (by an external power supply spike, for example), the OPENLED pull-down will be de-asserted and the PWMOUT pin will be driven low to protect the LEDs from an overcurrent event. Do not leave the FB pin open. If not used, connect to (Pin 3/Pin 13): Connection Point for the Negative Terminal of the current Feedback Resistor.