LT3518 - Full-Featured LED Driver with 2.3A Switch …

1 LT351813518ffFor more information Full-Featured LED Driver with Switch CurrentThe LT 3518 is a current mode DC/DC converter with an internal , 45V Switch specifically designed to drive LEDs. The LT3518 operates as a LED Driver in boost, buck mode and buck-boost mode. It combines a traditional voltage loop and a unique current loop to operate as a constant-current source or constant-voltage source. Pro-grammable switching frequency allows optimization of the external components for efficiency or component size. The switching frequency of the LT3518 can be synchronized to an external clock signal. The LED current is externally programmable with a 100mV sense resistor. The external PWM input provides 3000:1 LED dimming. The CTRL pin provides further 10:1 dimming ratio. The LT3518 is available in the tiny footprint 16-lead QFN (4mm 4mm) and the 16-pin TSSOP package. The LT3518 provides a complete solution for both constant-voltage and constant-current applications.

2 N3000:1 True Color PWM Dimming Ratio , 45V Internal Switch n100mV High Side Current Sense nOpen LED Protection nAdjustable Frequency: 250kHz to nWide Input Voltage Range: nOperation from 3V to 30V nTransient Protection to 40V nOperates in Boost, Buck Mode and Buck-Boost Mode nGate Driver for PMOS LED Disconnect nConstant-Current and Constant-Voltage Regulation nCTRL Pin Provides 10:1 Analog Dimming nLow Shutdown Current: <1 A nAvailable in (4mm 4mm) 16-Lead QFN and 16-Pin TSSOP Packages nDisplay Backlighting nAutomotive and Avionic Lighting nIllumination Buck Mode LED DriverEfficiencyL, LT, LTC and LTM are registered trademarks and True Color PWM is a trademark of Analog Devices Inc. All other trademarks are the property of their respective owners. Protected by Patents, including 7199560, 7321203, 7746300. Patent Pending. F15 F68m DUTY CYCLE (%)040 EFFICIENCY (%)5060708090100204060803518 TA01b100 CTRL = VREF typical applicationLT351823518ffFor more information MaxiMuM ratingsVIN, SHDN, PWM, TGEN (Note 3).

3 40 VSW, ISP, ISN, TG ..45 VTG Pin Below ISP Pin ..10 VFB, SYNC, SS, CTRL ..6 VVC, RT, VREF ..3 VOperating Junction Temperature Range (Notes 2, 4) LT3518E .. 40 C to 125 C LT3518I .. 40 C to 125 C LT3518H .. 40 C to 150 C(Note 1)161514135678 TOP VIEW17UF PACKAGE16-LEAD (4mm 4mm) PLASTIC QFN91011124321 SWSWVINSHDNFBVCCTRLPWMTGISPISNTGENVREFRT SYNCSS TJMAX = 150 C, JA = 36 C/WEXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCBFE PACKAGE16-LEAD PLASTIC TSSOP12345678 TOP VIEW161514131211109 VINSHDNVREFRTSYNCSSPWMCTRLSWSWTGISPISNTG ENFBVC17 GND TJMAX = 150 C, JA = 40 C/W, JC(PAD) = 10 C/Wpin conFigurationorDer inForMationLEAD FREE FINISHTAPE AND REELPART MARKING*PACKAGE DESCRIPTIONTEMPERATURE RANGELT3518 EUF#PBFLT3518 EUF#TRPBF351816-Lead (4mm 4mm) Plastic QFN 40 C to 125 CLT3518 IUF#PBFLT3518 IUF#TRPBF351816-Lead (4mm 4mm) Plastic QFN 40 C to 125 CLT3518 HUF#PBFLT3518 HUF#TPBF351816-Lead (4mm 4mm) Plastic QFN 40 C to 150 CLT3518 EFE#PBFLT3518 EFE#TRPBF3518FE16-Lead Plastic TSSOP 40 C to 125 CLT3518 IFE#PBFLT3518 IFE#TRPBF3518FE16-Lead Plastic TSSOP 40 C to 125 CLT3518 HFE#PBFLT3518 HFE#TRPBF3518FE16-Lead Plastic TSSOP 40 C to 150 CConsult LTC Marketing for parts specified with wider operating temperature ranges.

4 *The temperature grade is identified by a label on the shipping 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: Some packages are available in 500 unit reels through designated sales channels with #TRMPBF Temperature Range QFN .. 65 C to 150 C TSSOP .. 65 C to 150 CLead Temperature (Soldering, 10 sec) TSSOP ..300 #orderinfoLT351833518ffFor more information characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C. (Note 2) VIN = 5V, SHDN = 5V, PWM = 5V unless otherwise VIN Operating Voltage3 VMaximum VIN Operating VoltageContinuous Operation (Note 3)30 VCurrent Sense Voltage (VISP VISN)VCTRL = 2V, VISP = 24V, VC = 1V VCTRL = 2V, VISP = 0V, VC = 1Vl96100 100103mV mV10% Scale Current Sense Voltage (VISP VISN)VCTRL = 100mV, VISP = 24V, VC = 1V9mV Current Sense Voltage Line Regulation2V < VISP < Supply CurrentPWM > , VC = 0V PWM = 0V SHDN = 0V6 1mA mA ASwitching FrequencyRT = RT = RT = 270 MHz MHz kHzRT Voltage1 VSoft-Start Pin CurrentSS = , Out of Pin6912 ASYNC Pull-Down Current (Into the Pin)VSYNC = 2V60 ASYNC Input Input Duty CycleRT = (250kHz) SYNC = 300kHz Clock Signal, RT = RT = (1 MHz) RT = ( )

5 L95 94 8597 96 90 74% % % % Switch Current VCESATISW = Leakage CurrentVSW = 45V, PWM = 0V2 ACTRL Input Bias CurrentCurrent Out of Pin, VCTRL = Amplifier Transconductance550 SVC Output Impedance1000k VC Idle Input Bias CurrentPWM = 0, VC = 1V 20020nAFB Pin Input Bias CurrentCurrent Out of Pin, VFB = Pin , ISN Idle Input Bias CurrentPWM = 0V300nAISP , ISN Full-Scale Input Bias CurrentISP Tied to ISN, VISP = 24V, VCTRL = 2V20 ASHDN Voltage Voltage Low 40 C TJ 125 C 125 C < TJ 150 VSHDN Pin Bias Current60100 APWM Input High Input Low Voltage 40 C TJ 125 C 125 C < TJ 150 VPWM Pin Bias Current60120 ALT351843518ffFor more information characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C.

6 (Note 2) VIN = 5V, SHDN = 5V, PWM = 5V unless otherwise 1: 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 LT3518E is 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 LT3518I is guaranteed over the full 40 C to 125 C operating junction temperature range. The LT3518H is guaranteed over the full 40 C to 150 C operating junction temperature range. Operating lifetime is derated at junction temperatures greater than 125 C. Note 3: Absolute maximum voltage at VIN, SHDN, PWM and TGEN pins is 40V for nonrepetitive 1 second transients and 30V for continuous 4: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions.

7 Junction temperature will exceed the maximum operating junction temperature when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device Input High Input Low Pin Bias CurrentTGEN = 5V100200 AVREF Pin VoltageIREF = 100 Pin Voltage Line Regulation3V < VIN < Turn-On DelayCLOAD = 1nF Between ISP and TG200nsGate Turn-Off DelayCLOAD = 1nF Between ISP and TG200nsTop Gate Drive VGS (VISP VTG)VISP = 24V, TGEN = 5V PWM = 0V7 0 V VLT351853518ffFor more information perForMance characteristicsVISP VISN Threshold vs VCTRLS witch Current Limit vs Duty CycleOscillator Frequency vs RTVISP VISN Threshold vs TemperatureSwitch Current Limit vs TemperatureOscillator Frequency vs TemperatureVCTRL (V)00 VISP VISN THRESHOLD (mV) = 5 VVISP = 24 VVC = 1 VTA = 25 CDUTY CYCLE (%)00 CURRENT LIMIT (A) G02100TA = 25 CRT (k )1100 OSCILLATOR FREQUENCY (kHz)100010000101003518 G03TA = 25 CTEMPERATURE ( C) 40 VISP VISN THRESHOLD (mV)

8 103203518 G0410098 20 04097961041021019960 80 100 120 140 160 VIN = 5 VVISP = 24 VVC = 1 VVCTRL = 2 VTEMPERATURE ( C) 40 LIMIT (A) 1060853518 135 160 VIN = 5 VTEMPERATURE ( C) 40 FREQUENCY (MHz) 120 140 VIN = 5 VRT = Voltage vs TemperatureVISP VISN Threshold vs VISPVISP (V)0 VISP VISN THRESHOLD (mV)101103105403518 G07999710010210498969510203050 VCTRL = 2 VVIN = 5 VTA = 25 CVC = 1 VTEMPERATURE ( C) (V) 20 020 403518 G0860 80 100 120 140 160 VIN = 5 VQuiescent Current vs VINVIN (V)0 VIN CURRENT (mA)456403518 G09320102030187TA = 25 CVC = 0 VLT351863518ffFor more information perForMance characteristicsFB Pin Threshold vs TemperaturePMOS Turn-OnPMOS Turn-Offpin FunctionsSW: Switch Pin. Minimize trace at this pin to reduce : Input Supply Pin. Must be locally : Shutdown Pin. Tie to or higher to enable device or or less to disable device. VREF: Reference Output Pin.

9 This pin can supply up to 100 A. RT: Switching Frequency Adjustment Pin. Set switching frequency using a resistor to GND (see Typical Performance Characteristics for values). For SYNC function, choose the resistor to program a frequency 20% slower than the SYNC pulse frequency. Do not leave this pin : Frequency Synchronization Pin. Tie an external clock signal here. RT resistor should be chosen to pro-gram a switching frequency 20% slower than SYNC pulse frequency. Synchronization (power Switch turn-on) occurs a fixed delay after the rising edge of SYNC. Tie the SYNC pin to ground if this feature is not used. SS: Soft-Start Pin. Place a soft-start capacitor here. Leave the pin open if not in use. PWM: Pulse Width Modulated Input Pin. Signal low turns off channel, disables the main Switch and makes the TG pin high. Tie the PWM pin to SHDN pin if not used. There is an equivalent 50k resistor from PWM pin to ground : LED Current Adjustment Pin.

10 Sets voltage across sense resistor between ISP and ISN. Connect directly to VREF for full-scale threshold of 100mV, or use signal values between GND and 1V to modulate LED current. Tie the CTRL pin to the VREF pin if not : gm Error Amplifier Output Pin. Stabilize the loop with an RC network or compensating C. FB: Voltage Loop Feedback Pin. Works as overvoltage protection for LED drivers. If FB is higher than 1V, the main Switch is turned : Top Gate Enable Input Pin. Tie to or higher to enable the PMOS Driver function. Tie the TGEN pin to ground if TG function is not used. There is an equivalent 40k resistor from TGEN pin to ground : Current Sense ( ) Pin. The inverting input to the current sense : Current Sense (+) Pin. The noninverting input to the current sense amplifier. Also serves as positive rail for TG pin Driver . TG: Top Gate Driver Output. An inverted PWM sig-nal drives series PMOS device between VISP and (VISP 7V).