LT3496 Triple Output LED Driver Features Description n True Color PWM™ Dimming Delivers Up to 3000:1 The LT®3496 is a triple output DC/DC converter designed Dimming Ratio to operate as a constant-current source and is ideal for n Built-In Gate Driver for PMOS LED Disconnect driving LEDs. The LT3496 works in buck, boost or buck- n Three Independent Driver Channels with 750mA, boost mode. The LT3496 uses a fixed frequency, current 45V Internal Switches mode architecture resulting in stable operation over a n Operates in Buck, Boost, Buck-Boost Modes wide range of supply and output voltages. A frequency n CTRL Pin Accurately Sets LED Current Sense adjust pin allows the user to program switching frequency Threshold Over a Range of 10mV to 100mV between 330kHz and 2.1MHz to optimize efficiency and n Adjustable Frequency: 330kHz to 2.1MHz external component size. n Open LED Protection The LT3496 supports 3000:1 dimming control on each n Wide V Supply Range: IN channel. Each of the three regulators is independently Operation from 3V to 30V operated by that channel’s PWM signal. The PWM feature Transient Protection to 40V allows precise adjustment of the color mixing or dimming n Surface Mount Components ratio of the LED source. Each of the three channels has n 28-Lead (4mm × 5mm) QFN and TSSOP Packages a built-in gate driver to drive an external LED-disconnect P-channel MOSFET, allowing high dimming range. The applications output current range of each channel of the LT3496 is programmed with an external sense resistor. n RGB Lighting n Billboards and Large Displays The CTRL pins are used to adjust the LED currents either n Automotive and Avionic Lighting for analog dimming or overtemperature protection. n Constant-Current Sources L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and ThinSOT and True Color PWM are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 7199560, 7321203, and others pending. typical application High Dimming Ratio Triple Output LED Power Supply PVIN 42V CAP1 CAP2 CAP3 1µF (cid:115)3 200mΩ 200mΩ 200mΩ 3000:1 PWM Dimming at 120Hz LED1 LED2 LED3 TG1 TG2 TG3 PWM 5V/DIV 7 LEDs 0.5A 0.5A 0.5A IL 0.5A/DIV 0.47µF 0.47µF 0.47µF ILED 18µH 18µH 18µH 0.5A/DIV 0.5µs/DIV 3496 TA01b SW1 SW2 SW3 TG1, TG2, TG3 CAP1, CAP2, CAP3 VC1, VC2, VC3 3V TO 2V4IVN LVEIND1, LED2, LED3 LT3496 CTRL1, CTRL2, CTVRRLE3F 22k PWM1, PWM2, PWM3 PWM1, PWM2, PWM3 fADJ 470pF 1µF SHDN SHDN GND OVP1, OVP2, OVP3 3496 TA01a 3496ff 

LT3496 absolute MaxiMuM ratings (Note 1) V (Note 4) ...............................................................40V Operating Junction Temperature Range (Notes 2, 6) IN SW1, SW2, SW3, LED1, LED2, LED3, LT3496E ............................................–40°C to 125°C CAP1, CAP2, CAP3....................................................45V LT3496I .............................................–40°C to 125°C TG1, TG2, TG3 ....................................CAP – 10V to CAP LT3496H ............................................–40°C to 150°C PWM1, PWM2, PWM3 ..............................................20V Storage Temperature Range V , CTRL1, CTRL2, CTRL3, f , VC1, VC2, VC3, QFN ....................................................–65°C to 150°C REF ADJ OVP1, OVP2, OVP3 ..................................................2.5V TSSOP .................................................65°C to 125°C SHDN (Note 4) ...........................................................V Lead Temperature (Soldering, 10 sec) IN TSSOP ..............................................................300°C pin conFiguration TOP VIEW SHDN 1 28 VIN TOP VIEW PPWWMM32 23 2276 TLGED33 PWM2 PWM3 SHDN VIN TG3 LED3 28 27 26 25 24 23 PWM1 4 25 CAP3 PWM1 1 22 CAP3 VREF 5 24 SW3 VREF 2 21 SW3 CTRL3 6 23 SW2 CTRL3 3 20 SW2 CTRL2 7 22 CAP2 CTRL2 4 19 CAP2 29 29 CTRL1 8 21 LED2 CTRL1 5 18 LED2 fADJ 9 20 TG2 fADJ 6 17 TG2 VC3 10 19 SW1 VC3 7 16 SW1 VC2 11 18 CAP1 VC2 8 15 CAP1 VC1 12 17 LED1 9 10 11 12 13 14 1 3 2 1 1 1 OVP3 13 16 TG1 VC VP VP VP TG ED O O O L OVP2 14 15 OVP1 UFD PACKAGE 28-LEAD (4mm (cid:115) 5mm) PLASTIC QFN 28-LEAFDE PPLAACSKTAIGCE TSSOP EXPOSED PAD (PθINJA 2=9 3) 4IS°C G/WND, θ, JMC U=S 2T. 7B°EC /SWO LDERED TO PCB θJA = 30°C/W, θJC = 10°C/W EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB orDer inForMation LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3496EFE#PBF LT3496EFE#TRPBF 3496FE 28-Lead Plastic TSSOP –40°C to 125°C LT3496IFE#PBF LT3496IFE#TRPBF 3496FE 28-Lead Plastic TSSOP –40°C to 125°C LT3496EUFD#PBF LT3496EUFD#TRPBF 3496 28-Lead (4mm × 5mm) Plastic QFN –40°C to 125°C LT3496IUFD#PBF LT3496IUFD#TRPBF 3496 28-Lead (4mm × 5mm) Plastic QFN –40°C to 125°C LT3496HUFD#PBF LT3496HUFD#TRPBF 3496 28-Lead (4mm × 5mm) Plastic QFN –40°C to 150°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. *For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 3496ff 

LT3496 electrical characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C. V = 5V, V = 5V, CAP1, CAP2, CAP3 = 5V, PWM1, PWM2, PWM3 = 5V, A IN SHDN f = 0.5V, CTRL1, CTRL2, CTRL3 = 1.5V, OVP1, OVP2, OVP3 = 0V, unless otherwise noted. ADJ PARAMETER CONDITIONS MIN TYP MAX UNITS V Operation Voltage (Note 4) 3 30 V IN V Undervoltage Lockout 2.1 2.4 V IN Full-Scale LED Current Sense Voltage CAP1, CAP2, CAP3 = 24V 98 100 103 mV (V , V , V ) l 97 104 mV CAP1-LED1 CAP2-LED2 CAP3-LED3 One-Tenth Scale LED Current Sense Voltage CTRL1, CTRL2, CTRL3 = 100mV, CAP1, CAP2, CAP3 = 24V (V , V , V ) H-Grade l 7.5 10 13.5 mV CAP1-LED1 CAP2-LED2 CAP3-LED3 E-Grade, I-Grade l 7.5 10 12.5 mV CAP1, CAP2, CAP3 Operating Voltage 0V ≤ V ≤ 104mV 2.5 45 V CAP1-LED1 0V ≤ V ≤ 104mV CAP2-LED2 0V ≤ V ≤ 104mV CAP3-LED3 V Output Voltage I = 200µA, Current Out of Pin l 1.96 2 2.04 V REF REF V Line Regulation 3V ≤ V ≤ 40V, I = 10µA 0.03 %/V REF IN REF Quiescent Current in Shutdown SHDN = 0V 0.1 10 µA Quiescent Current Idle PWM1, PWM2, PWM3 = 0V 6 7.5 mA Quiescent Current Active (Not Switching) 11 14 mA Switching Frequency f = 1.5V 1900 2100 2300 kHz ADJ f = 0.5V 1300 kHz ADJ f = 0.1V 330 kHz ADJ Maximum Duty Cycle f = 1.5V (2.1MHz) l 70 78 % ADJ f = 0.5V (1.3MHz) 87 % ADJ f = 0.1V (330kHz) 97 % ADJ CTRL1, CTRL2, CTRL3 Input Bias Current Current Out of Pin, CTRL1, CTRL2, CTRL3 = 0.1V 20 100 nA f Input Bias Current Current Out of Pin, f = 0.1V 20 100 nA ADJ ADJ OVP1, OVP2, OVP3 Input Bias Current Current Out of Pin, OVP1, OVP2, OVP3 = 0.1V 10 100 nA OVP1, OVP2, OVP3 Threshold 0.95 1 1.05 V VC1, VC2, VC3 Idle Input Bias Current PWM1, PWM2, PWM3 = 0V –20 0 20 nA VC1, VC2, VC3 Output Impedance CAP1, CAP2, CAP3 = 24V 10 MΩ EAMP gm (ΔIVC/ΔVCAP-LED) CAP1, CAP2, CAP3 = 24V 200 µS SW1, SW2, SW3 Current Limit (Note 3) 750 1000 1250 mA SW1, SW2, SW3 V I = 500mA (Note 3) 260 mV CESAT SW SW1, SW2, SW3 Leakage Current SHDN = 0V, SW = 5V 2 µA CAP1, CAP2, CAP3 Input Bias Current 180 250 µA CAP1, CAP2, CAP3, LED1, LED2, LED3 Idle Input PWM1, PWM2, PWM3 = 0V 1 µA Bias Current CAP1, CAP2, CAP3, LED1, LED2, LED3 Input Bias SHDN = 0V 1 µA Current in Shutdown 3496ff 

LT3496 electrical characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C. V = 5V, V = 5V, CAP1, CAP2, CAP3 = 5V, PWM1, PWM2, PWM3 = 5V, A IN SHDN f = 0.5V, CTRL1, CTRL2, CTRL3 = 1.5V, OVP1, OVP2, OVP3 = 0V, unless otherwise noted. ADJ PARAMETER CONDITIONS MIN TYP MAX UNITS SHDN Input Low Voltage 0.4 V SHDN Input High Voltage 1.5 V SHDN Pin Current V = 5V, Current Into Pin 65 100 µA SHDN PWM1, PWM2, PWM3 Input Low Voltage 0.4 V PWM1, PWM2, PWM3 Input High Voltage 1.2 V PWM1, PWM2, PWM3 Pin Current Current Into Pin 160 210 µA Gate Off Voltage CAP1, CAP2, CAP3 = 40V, 0.1 0.3 V (CAP1 – TG1, CAP2 – TG2, CAP3 – TG3) PWM1, PWM2, PWM3 = 0V Gate On Voltage CAP1, CAP2, CAP3 = 40V 5.5 6.5 7.5 V (CAP1 – TG1, CAP2 – TG2, CAP3 – TG3) Gate Turn-On Delay C = 300pF, CAP1, CAP2, CAP3 = 40V (Note 5) 110 ns LOAD Gate Turn-Off Delay C = 300pF, CAP1, CAP2, CAP3 = 40V (Note 5) 110 ns LOAD Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 3: Current flows into pin. Current limit and switch V is CESAT may cause permanent damage to the device. Exposure to any Absolute guaranteed by design and/or correlation to static test. Maximum Rating condition for extended periods may affect device Note 4: Absolute maximum voltage at the V and SHDN pins is 40V for IN reliability and lifetime. nonrepetitive 1 second transients, and 30V for continuous operation. Note 2: The LT3496E is guaranteed to meet performance specifications Note 5: Gate turn-on/turn-off delay is measured from 50% level of PWM from 0°C to 125°C junction temperature. Specifications over the –40°C voltage to 90% level of gate on/off voltage. to 125°C operating junction temperature range are assured by design, Note 6: The LT3496 includes overtemperature protection that is intended characterization and correlation with statistical process controls. The to protect the device during momentary overload conditions. Junction LT3496I is guaranteed over the full –40°C to 125°C operating junction temperature will exceed the maximum operating junction temperature temperature range. The LT3496H is guaranteed over the full –40°C to when overtemperature protection is active. Continuous operating above 150°C operating junction temperature range. High junction temperatures the specified maximum operating junction temperature may impair device degrade operating lifetimes. Operating lifetime is derated at junction reliability. temperatures greater than 125°C. 3496ff 

LT3496 typical perForMance characteristics (T = 25°C unless otherwise noted) A Switch Current Limit Quiescent Current Switch On Voltage vs Duty Cycle 14 500 1000 PWM1, PWM2, PWM3 = 5V 12 400 A) 800 m INPUT CURRENT (mA) 14806 PWM1, PWM2, PWM3 = 0V SWITCH VOLTAGE (mV) 230000 WITCH CURRENT LIMIT ( 460000 100 S 200 2 VC = GND, NOT SWITCHING 0 0 0 0 10 20 30 40 0 200 400 600 800 1000 0 20 40 60 80 100 VIN (V) SWITCH CURRENT (mA) DUTY CYCLE (%) 3496 G01 3496 G02 3496 G03 Switch Current Limit vs Reference Voltage Temperature vs Temperature Switch Frequency vs f ADJ 1200 2.04 2250 2.03 2000 1000 A) 2.02 kHz)1750 NT LIMIT (m 680000 V (V)REF 22..0001 REQUENCY (111025050000 CURRE 400 11..9989 WITCH F 750 S 500 200 1.97 250 0 1.96 0 –50 –25 0 25 50 75 100 125 150 –50 –25 0 25 50 75 100 125 150 0 0.2 0.4 0.6 0.8 1.0 1.2 TEMPERATURE (°C) TEMPERATURE (°C) fADJ (V) 3496 G04 3496 G05 3496 G06 3496ff 

LT3496 typical perForMance characteristics (T = 25°C unless otherwise noted) A Switch Frequency vs Temperature VCAP-LED Threshold vs CTRL VCAP-LED Threshold vs VCAP 2.4 120 103 fADJ = 1.2V VCAP = 24V CTRL = 1.2V 2.3 100 102 Hz) mV) mV) CY (M 2.2 OLD ( 80 OLD (101 N H H QUE 2.1 RES 60 HES100 WITCH FRE 2.0 THCAP-LED 40 TRCAP-LED 99 S V V 1.9 20 98 1.8 0 97 –50 –25 0 25 50 75 100 125 150 0 0.2 0.4 0.6 0.8 1 1.2 0 10 20 30 40 50 TEMPERATURE (°C) CTRL (V) VCAP (V) 3496 G07 3496 G08 3496 G09 V Threshold vs CAP-LED Temperature PMOS Turn On Waveforms PMOS Turn Off Waveforms 103 CTRL = 1.2V VCAP = 24V V) 102 5V 5V D (m 101 PWM PWM OL 0V 0V H S RE 100 H TD 40V 40V P-LE 99 TG TG A VC 30V 30V 98 97 –50 –25 0 25 50 75 100 125 150 VCAP = 40V 200ns/DIV 3496 G11 VCAP = 40V 200ns/DIV 3496 G12 TEMPERATURE (°C) 3496 G10 3496ff 

LT3496 pin Functions PWM1, PWM2, PWM3: Pulse Width Modulated Inputs. When the PWM pin is low, the TG pin pulls up to CAP to Signal low turns off the respective converter, reduces turn off the external MOSFET. When the PWM pin is high, quiescent supply current and causes the VC pin for that the external MOSFET turns on. Respective CAP-TG is converter to become high impedance. PWM pin must not limited to 6.5V to protect the MOSFET. Leave open if the be left floating; tie to V if not used. external MOSFET is not used. REF V : Reference Output Pin. Can supply up to 200µA. The LED1, LED2, LED3: Noninverting Inputs of Current Sense REF nominal Output Voltage is 2V. Error Amplifiers. Connect directly to LED current sense resistor terminal for current sensing of the respective CTRL1, CTRL2, CTRL3: LED Current Adjustment Pins. Sets converter voltage across external sense resistor between CAP and LED pins of the respective converter. Setting CTRL voltage CAP1, CAP2, CAP3: Inverting Inputs of Current Sense Error to be less than 1V will control the current sense voltage to Amplifiers. Connect directly to other terminal of LED current be one-tenth of CTRL voltage. If CTRL voltage is higher than sense resistor terminal of the respective converter. 1V, the default current sense voltage is 100mV. The CTRL SW1, SW2, SW3: Switch Pins. Collector of the internal pin must not be left floating. NPN power switch of the respective converter. Connect f : Switching Frequency Adjustment Pin. Setting f to external inductor and anode of external Schottky recti- ADJ ADJ voltage to be less than 1V will adjust switching frequency fier of the respective converter. Minimize the metal trace up to 2.1MHz. If f voltage is higher than 1V, the default area connected to this pin to minimize electromagnetic ADJ switching frequency is 2.1MHz. The f pin must not be interference. ADJ left floating. V : Input Supply Pin. Must be locally bypassed. Powers IN VC1, VC2, VC3: Error Amplifier Compensation Pins. Con- the internal control circuitry. nect a series RC from these pins to GND. SHDN: Shutdown Pin. Used to shut down the switching OVP1, OVP2, OVP3: Open LED Protection Pins. A voltage regulator and the internal bias circuits for all three convert- higher than 1V on OVP turns off the internal main switch ers. Tie to 1.5V or greater to enable the device. Tie below of the respective converter. Tie to ground if not used. 0.4V to turn off the device. TG1, TG2, TG3: The Gate Driver Output Pins for Dis- Exposed Pad: Signal Ground and Power Ground. Solder connnect P-Channel MOSFETs. One for each converter. paddle directly to ground plane. 3496ff 

LT3496 block DiagraM D1 +VSENSE– ILED M1 LED1 C2 L1 VIN RSENSE 0.2Ω C1 CAP1 LED1 TG1 PWM1 SW1 R3 A7 OVP1 MOSFET DRIVER R4 VC1 – RC EAMP + PWM1 A6 NPN CC A1 1V + DRIVER + V1 – – A4 A5 Q1 R1 2k 1V + VC – SR LAA3TCH CTRL1 + A8 Q3 A2 R Q – + S CTRL SLOPE PWM ISENS2 BUFFER COMPARATOR + A10 R2 GND 20k – REPLICATED FOR EACH CHANNEL VIN VIN INTERNAL C3 SHDN REGULATOR VIN AND UVLO ISRC 200µA VREF RAMP GENERATOR – A9 Q2 OSCILLATOR 2V + REFERENCE fADJ R5 SHARED COMPONENTS 3496 BD C4 R6 Figure 1. LT3496 Block Diagram Working in Boost Configuration 3496ff 

LT3496 applications inForMation Operation the PWM1 pin is pulled low, Q1 is turned off. Converter 1 stops operating, M1 is turned off, disconnects LED1 and The LT3496 uses a fixed frequency, current mode control stops current draw from output capacitor C2. The VC1 scheme to provide excellent line and load regulation. Op- pin is also disconnected from the internal circuitry and eration can be best understood by referring to the Block draws minimal current from the compensation capacitor Diagram in Figure 1. The oscillator, ramp generator, refer- C . The VC1 pin and the output capacitor store the state ence, internal regulator and UVLO are shared among the C of the LED1 current until PWM1 is pulled up again. This three converters. The control circuitry, power switch etc., leads to a highly linear relationship between pulse width are replicated for each of the three converters. Figure 1 and output light, and allows for a large and accurate dim- shows the shared circuits and only converter 1 circuits. ming range. A P-channel MOSFET with smaller total gate If the SHDN pin is tied to ground, the LT3496 is shut charge (Q ) improves the dimming performance, since G down and draws minimal current from VIN. If the SHDN it can be turned on and off faster. Use a MOSFET with a pin exceeds 1.5V, the internal bias circuits turn on. The Q lower than 10nC, and a minimum V of –1V to –2V. G TH switching regulators start to operate when their respective Don’t use a Low V PMOS. To optimize the PWM control TH PWM signal goes high. of all the three channels, the rising edge of all the three PWM signals should be synchronized. The main control loop can be understood by following the operation of converter 1. The start of each oscillator cycle In the applications where high dimming ratio is not required, sets the SR latch, A3, and turns on power switch Q1. The M1 can be omitted to reduce cost. In these conditions, signal at the noninverting input (SLOPE node) of the PWM TG1 should be left open. The PWM dimming range can be comparator A2 is proportional to the sum of the switch further increased by using CTRL1 pin to linearly adjust the current and oscillator ramp. When SLOPE exceeds VC1 current sense threshold during the PWM1 high state. (the output of the error amplifier A1), A2 resets the latch and turns off the power switch Q1 through A4 and A5. Loop Compensation In this manner, A10 and A2 set the correct peak current Loop compensation determines the stability and transient level to keep the output in regulation. Amplifier A8 has performance. The LT3496 uses current mode control to two noninverting inputs, one from the 1V internal voltage regulate the output, which simplifies loop compensation. reference and the other one from the CTRL1 pin. Whichever To compensate the feedback loop of the LT3496, a series input is lower takes precedence. A8, Q3 and R1 force V1, resistor-capacitor network should be connected from the the voltage across R1, to be one tenth of either 1V or the VC pin to GND. For most applications, the compensation voltage of CTRL1 pin, whichever is lower. V is the SENSE capacitor should be in the range of 100pF to 1nF. The com- voltage across the sensing resistor, R , which is con- SENSE pensation resistor is usually in the range of 5k to 50k. nected in series with the LEDs. V is compared to V1 SENSE by A1. If V is higher than V1, the output of A1 will To obtain the best performance, tradeoffs should be made SENSE decrease, thus reducing the amount of current delivered to in the compensation network design. A higher value of LEDs. In this manner the current sensing voltage V compensation capacitor improves the stability and dim- SENSE is regulated to V1. ming range (a larger capacitance helps hold the VC voltage when the PWM signal is low). However, a large compen- Converters 2 and 3 are identical to converter 1. sation capacitor also increases the start-up time and the PWM Dimming Control time to recover from a fault condition. Similarly, a larger compensation resistor improves the transient response LED1 can be dimmed with pulse width modulation us- but may reduce the phase margin. A practical approach ing the PWM1 pin and an external P-channel MOSFET, is to start with one of the circuits in this data sheet that M1. If the PWM1 pin is pulled high, M1 is turned on by is similar to your application and tune the compensation internal driver A7 and converter 1 operates nominally. network to optimize the performance. The stability, PWM A7 limits CAP1-TG1 to 6.5V to protect the gate of M1. If 3496ff 

LT3496 applications inForMation dimming waveforms and the start-up time should be Input Capacitor Selection checked across all operating conditions. For proper operation, it is necessary to place a bypass capacitor to GND close to the V pin of the LT3496. A Open-LED Protection IN 1µF or greater capacitor with low ESR should be used. A The LT3496 has open-LED protection for all the three ceramic capacitor is usually the best choice. converters. As shown in Figure 1, the OVP1 pin receives In the buck mode configuration, the capacitor at PV has the output voltage (the voltage across the output capacitor) IN large pulsed currents due to the current returned though feedback signal from an external resistor divider. OVP1 the Schottky diode when the switch is off. For the best voltage is compared with a 1V internal voltage reference by reliability, this capacitor should have low ESR and ESL comparator A6. In the event the LED string is disconnected and have an adequate ripple current rating. The RMS or fails open, converter 1 output voltage will increase, caus- input current is: ing OVP1 voltage to increase. When OVP1 voltage exceeds 1V, the power switch Q1 will turn off, and cause the output I =I • (1–D)•D voltage to decrease. Eventually, OVP1 will be regulated to IN(RMS) LED 1V and the output voltage will be limited. In the event one where D is the switch duty cycle. A 1µF ceramic type ca- of the converters has an open-LED protection, the other pacitor placed close to the Schottky diode and the ground converters will continue functioning properly. plane is usually sufficient for each channel. Switching Frequency and Soft-Start Output Capacitor Selection The LT3496 switching frequency is controlled by f pin ADJ The selection of output filter capacitor depends on the load voltage. Setting f voltage to be less than 1V will reduce ADJ and converter configuration, i.e., step-up or step-down. switching frequency. For LED applications, the equivalent resistance of the LED If f voltage is higher than 1V, the default switching is typically low, and the output filter capacitor should be ADJ frequency is 2.1MHz. In general, a lower switching fre- large enough to attenuate the current ripple. quency should be used where either very high or very To achieve the same LED ripple current, the required filter low switch duty cycle is required or higher efficiency is capacitor value is larger in the boost and buck-boost mode desired. Selection of a higher switching frequency will applications than that in the buck mode applications. For the allow use of low value external components and yield a LED buck mode applications, a 0.22µF ceramic capacitor smaller solution size and profile. is usually sufficient for each channel. For the LED boost Connecting f pin to a lowpass filter (R5 and C4 in and buck-boost applications, a 1µF ceramic capacitor is ADJ Figure 1) from the REF pin provides a soft-start function. usually sufficient for each channel. If higher LED current During start-up, f voltage increases slowly from 0V to ripple can be tolerated, a lower output capacitance can be ADJ the setting voltage. As a result, the switching frequency selected to reduce the capacitor’s cost and size. increases slowly to the setting frequency. This function Use only ceramic capacitors with X7R or X5R dielectric, limits the inrush current during start-up. as they are good for temperature and DC bias stability of the capacitor value. All ceramic capacitors exhibit loss of Undervoltage Lockout capacitance value with increasing DC voltage bias, so it The LT3496 has an undervoltage lockout circuit that may be necessary to choose a higher value capacitor to get shuts down all the three converters when the input volt- the required capacitance at the operation voltage. Always age drops below 2.4V. This prevents the converter from check that the voltage rating of the capacitor is sufficient. switching in an erratic mode when powered from a low Table 1 shows some recommended capacitor vendors. supply voltage. 3496ff 0

LT3496 applications inForMation Table 1. Ceramic Capacitor Manufacturers Table 2. Surface Mount Inductors VENDOR TYPE SERIES VALUE DCR SIZE Taiyo Yuden Ceramic X5R, X7R PART NUMBER (µH) (Ω MAX) IRMS (A) W × L × H (mm3) Sumida AVX Ceramic X5R, X7R CMD4D06 2.2 0.116 0.95 3.5 × 4.3 × 0.8 Murata Ceramic X5R, X7R 3.3 0.174 0.77 Kemet Ceramic X5R, X7R CDRH3D16 2.2 0.072 1.20 3.8 × 3.8 × 1.8 Inductor Selection 3.3 0.085 1.10 4.7 0.105 0.90 Several inductors that work well with the LT3496 are listed CDRH4D28 10 0.128 1.00 5.0 × 5.0 × 3.0 in Table 2. However, there are many other manufacturers 15 0.149 0.76 and devices that can be used. Consult each manufacturer CDRH5D28 22 0.122 0.9 6.0 × 6.0 × 3.0 for more detailed information and their entire range of 33 0.189 0.75 parts. Ferrite core inductors should be used to obtain the CooperET best efficiency. Choose an inductor that can handle the necessary peak current without saturating, and ensure that SD3112 2.2 0.140 0.97 3.1 × 3.1 × 1.2 the inductor has a low DCR (copper-wire resistance) to 3.3 0.165 0.90 minimize I2R power losses. An inductor with a magnetic 4.7 0.246 0.74 shield should be used to prevent noise radiation and cross SD14 10 0.2058 1.1 5.0 × 5.0 × 1.4 coupling among the three channels. SD20 15 0.1655 1.25 5.0 × 5.0 × 2.0 22 0.2053 1.12 Diode Selection SD25 33 0.2149 1.11 5.0 × 5.0 × 2.5 The Schottky diode conducts current during the interval Taiyo Yuden when the switch is turned off. Select a diode V rated NR3015 2.2 0.06 1.48 3.0 × 3.0 × 1.5 R for the maximum SW voltage. It is not necessary that 4.7 0.12 1.02 the forward current rating of the diode equal the switch NP04SZB 4.7 0.075 1.6 4.0 × 4.0 × 1.8 current limit. The average current, I , through the diode 10 0.100 1.2 F is a function of the switch duty cycle. Select a diode with 15 0.180 0.95 forward current rating of: 22 0.210 0.77 I = I • (1 – D) F L Table 3. Schottky Diodes where I is the inductor current. L PART NUMBER V (V) I (A) PACKAGE R F If using the PWM feature for dimming, it is important to ZETEX consider diode leakage, which increases with the tem- ZLLS350 40 0.38 SOD523 perature from the output during the PWM low interval. ZLLS400 40 0.52 SOD323 Therefore, choose the Schottky diode with sufficient low leakage current. Table 3 shows several Schottky diodes that work well with the LT3496. 3496ff 

LT3496 applications inForMation Programming the LED Current voltages to ensure that a junction temperature of 125°C is not exceeded. This is especially important when operat- The LED current of each channel is programmed by con- ing at high ambient temperatures. The exposed pad on necting an external sense resistor R in series with SENSE the bottom of the package must be soldered to a ground the LED load, and setting the voltage regulation threshold plane. This ground should then be connected to an internal across that sense resistor using CTRL input. If the CTRL copper ground plane with thermal vias placed directly voltage, V , is less than 1V, the LED current is: CTRL under the package to spread out the heat dissipated by V the LT3496. I = CTRL LED 10•R SENSE Board Layout If V is higher than 1V, the LED current is: CTRL The high speed operation of the LT3496 demands careful 100mV attention to board layout and component placement. The I = LED exposed pad of the package is the only GND terminal of R SENSE the IC and is important for thermal management of the The CTRL pins should not be left open. The CTRL pin IC. Therefore, it is crucial to achieve a good electrical can also be used in conjunction with a PTC thermistor to and thermal contact between the exposed pad and the provide overtemperature protection for the LED load as ground plane of the board. Also, in boost configuration, shown in Figure 2. the Schottky rectifier and the capacitor between GND and the cathode of the Schottky are in the high frequency switching path where current flow is discontinuous. These 2V VREF elements should be placed so as to minimize the path 45k 50k between SW and the GND of the IC. To reduce electro- CTRL1 to CTRL3 magnetic interference (EMI), it is important to minimize the area of the SW node. Use the GND plane under SW 5k PTC to minimize interplane coupling to sensitive signals. To 3496 F02 obtain good current regulation accuracy and eliminate sources of channel to channel coupling, the CAP and LED Figure 2 inputs of each channel of the LT3496 should be run as separate lines back to the terminals of the sense resistor. Thermal Considerations Any resistance in series with CAP and LED inputs should The LT3496 is rated to a maximum input voltage of 30V be minimized. Finally, the bypass capacitor on the V sup- IN for continuous operation, and 40V for nonrepetitive one ply to the LT3496 should be placed as close as possible second transients. Careful attention must be paid to the to the V terminal of the device. IN internal power dissipation of the LT3496 at higher input 3496ff 

LT3496 typical applications Minimum BOM Buck Mode LED Driver PVIN C1-C3 42V CAP1 CAP2 CAP3 1µF 330mΩ 330mΩ 330mΩ (cid:115)3 LED1 LED2 LED3 7 LEDs 0.3A 0.3A 0.3A C4 C5 C6 0.22µF 0.22µF 0.22µF L1 L2 L3 15µH D1 D2 15µH 15µH D3 SW1 SW2 SW3 TG1, TG2, TG3 OPEN CAP1, CAP2, CAP3 VC1, VC2, VC3 V3IVN LVEIND1, LED2, LED3 LT3496 CTRL1, CTRL2, CTVRRLE3F 22k PWM1, PWM2, PWM3 PWM1, PWM2, PWM3 fADJ 470pF C7 1µF SHDN SHDN GND OVP1, OVP2, OVP3 3496 TA07a C1-C3, C7: MURATA GRM31MR71H105KA88 C4-C6: MURATA GRM21BR71H224KA01 D1-D3: DIODES DFLS160 L1-L3: TAIYO YUDEN NP04SZB 150M 300:1 PWM Dimming at 120Hz Efficiency 100 PWM = 3V PWM CTRL = 0V TO 1.2V 5V/DIV 95 IL %) 0.5A/DIV Y ( 90 C N E 0.5A/IDLEIVD FFICI 85 E 5µs/DIV 3496 TA07b 80 75 0 50 100 150 200 250 300 ILED (mA) 3496 TA07c 3496ff 

LT3496 typical applications Triple Boost 100mA × 10 LED Driver PVIN 12V C1 L1 2.2µF L2 L3 10µH 10µH 10µH D1 D2 D3 CAP1 CAP2 CAP3 C2 C3 C4 1µF 1Ω 1µF 1Ω 1µF 1Ω LED1 LED2 LED3 TG1 M1 TG2 M2 TG3 M3 825k 825k 825k OVP1 OVP2 OVP3 10 LEDs 100mA 10 LEDs 100mA 10 LEDs 100mA 20k 20k 20k SW1 SW2 SW3 TG1, TG2, TG3 CAP1, CAP2, CAP3 OVP1, OVP2, OVP3 LED1, LED2, LED3 VC1, VC2, VC3 V3IVN VIN LT3496 VREF 10k C5 PWM1, PWM2, PSWHMDN3 PSWHDMN1, PWM2, PWM3 GND CTRL1, CTRL2, CTfRALD3J 470pF 1µF C1: MURATA GRM31MR71C225KA35 3496 TA03a C2-C5: MURATA GRM31MR71H105KA88 D1-D3: DIODES DFLS160 L1-L3: TAIYO YUDEN NP04SZB 100M M1-M3: ZETEX ZXMP6A13F 3000:1 PWM Dimming at 120Hz Efficiency vs PWM Duty Cycle 95 CTRL = 2V 90 PWM 5V/DIV 85 %) 80 Y ( 75 IL NC 0.5A/DIV CIE 70 FI EF 65 ILED 0.1A/DIV 60 55 0.5µs/DIV 3496 TA03b 50 0 20 40 60 80 100 PWM DUTY CYCLE (%) 3496 TA03d 3496ff 

LT3496 typical applications Dual Boost LED Driver PVIN 12V C1 L1 2.2µF L2 L3 10µH 10µH 10µH D1 D2 D3 CAP1 CAP2 CAP3 C2 C3 C4 1µF 1Ω 1µF 1Ω 1µF 1Ω LED1 LED2 LED3 M1 M2 825k 825k 10 LEDs 100mA OVP1 10 LEDs 200mA OVP2-3 20k 20k SW1 TG1 SW2 SW3 TG2 OVP1, OVP2, OVP3 CAP1, CAP2, CAP3 TG3 OPEN 3V TO 1V2IVN LVEIND1, LED2, LED3 LT3496 VC1, VC2,V VRCE3F 10k C5 SPHWDMN PSWHDMN1, PWM2, PWM3 GND CTRL1, CTRL2, CTfRALD3J 470pF 1µF C1: MURATA GRM31MR71C225KA35 3496 TA04 C2-C5: MURATA GRM31MR71H105KA88 D1-D3: DIODES DFLS160 L1-L3: TAIYO YUDEN NP04SZB 100M M1, M2: ZETEX ZXMP6A13F Triple Boost 20mA × 8 LED Driver PVIN 5V C1 L1 2.2µF L2 L3 22µH 22µH 22µH D1 D2 D3 CAP1 CAP2 CAP3 C2 C3 C4 1µF 5Ω 1µF 5Ω 1µF 5Ω LED1 LED2 LED3 TG1 M1 TG2 M2 TG3 M3 825k 825k 825k OVP1 OVP2 OVP3 8 LEDs 20mA 8 LEDs 20mA 8 LEDs 20mA 20k 20k 20k SW1 SW2 SW3 TG1, TG2, TG3 CAP1, CAP2, CAP3 OVP1, OVP2, OVP3 LED1, LED2, LED3 VC1, VC2, VC3 V5IVN VIN LT3496 VREF 10k PWM1, PWM2, PWM3 PWM1, PWM2, PWM3 CTRL1, CTRL2, CTRL3 82k C5 1µF SHDN SHDN GND fADJ 470pF C1: MURATA GRM31MR71C225KA35 20k C2-C5: MURATA GRM31MR71H105KA88 D1-D3: ZETEX ZLLS350 3496 TA08a L1-L3: TAIYO YUDEN NP04SZB 220M M1-M3: ZETEX ZXMP6A13F 3496ff 

LT3496 typical applications Buck-Boost Mode 300mA × 6 LED Driver PVIN 10V TO 16V C1 2.2µF 300mA 6 LEDs L1 L2 L3 10µH 10µH 10µH 825k M1 OVP1-3 LED1 LED2 LED3 20k 1Ω 1Ω 1Ω CAP1 CAP2 CAP3 D1 D2 D3 C2 C3 C4 C5 C6 C7 0.1µF 1µF 0.1µF 1µF 0.1µF 1µF PVIN PVIN PVIN SW1 SW2 SW3 TG1 OVP1, OVP2, OVP3 CAP1, CAP2, CAP3 TG1, TG2, TG3 OPEN LED1, LED2, LED3 LT3496 VC1, VC2, VC3 3V TO 1V6IVN VIN VREF 10k PWM PWM1, PWM2, PWM3 fADJ C8 SHDN SHDN GND CTRL1, CTRL2, CTRL3 470pF 1µF C1: MURATA GRM31MR71E225KA93 3496 TA05 C2, C4, C6: MURATA GRM21BR71H104KA01B C3, C5, C7: MURATA GRM31MR71H105KA88 C8: MURATA GRM31MR71E105KA93 D1-D3: DIODES DFLS160 L1-L3: TAIYO YUDEN NP04SZB 100M M1: ZETEX ZXMP6A13F Triple Buck Mode LED Driver with Open LED Protection PVIN C1-C3 12V TO 40V CAP1 CAP2 CAP3 1µF 200mΩ 200mΩ 200mΩ (cid:115)3 LED1 LED2 LED3 TG1 M1 TG2 M2 M3 TG3 20k 20k 20k 0.5A 0.5A 0.5A C4 C5 C6 0.47µF 0.47µF 0.47µF 5.6k 5.6k 5.6k M4 M5 M6 OVP1 L1 L2 OVP2OVP1 L3 2k 10µH D1 D2 10µH 2k 2k 10µH D3 SW1 SW2 SW3 TG1, TG2, TG3 CAP1, CAP2, CAP3 OVP1, OVP2, OVP3 LED1, LED2, LED3 VC1, VC2, VC3 3V TO 2V4IVN VIN LT3496 VREF 22k C7 PWM1, PWM2, PWM3 PWM1, PWM2, PWM3 fADJ SHDN SHDN GND CTRL1, CTRL2, CTRL3 470pF 1µF C1-C3, C7: MURATA GRM31MR71H105KA88 3496 TA02 C4-C6: MURATA GRM188R71C474KA88 D1-D3: DIODES DFLS160 L1-L3: TAIYO YUDEN NP04SZB 100M M1-M3: ZETEX ZXMP6A13F M4-M6: PHILIPS BC858B 3496ff 

LT3496 package Description FE Package 28-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) exposed pad Variation EB 4.75 9.60 – 9.80* (.187) (.378 – .386) 4.75 (.187) 28 2726252423222120 19181716 15 6.60(cid:112)(cid:0)0.10 2.74 EXPOSED 4.50(cid:112)(cid:0)0.10 (.108) PAD HEAT SINK SEE NOTE 4 ON BOTTOM OF 6.40 0.45(cid:112)(cid:0)0.05 PACKAGE (2.1.7048) (.252) BSC 1.05(cid:112)(cid:0)0.10 0.65 BSC RECOMMENDED SOLDER PAD LAYOUT 1 2 3 4 5 6 7 8 9 10 11 12 1314 1.20 4.30 – 4.50* (.047) (.169 – .177) 0.25 MAX REF 0(cid:111) – 8(cid:111) 0.65 0.09 – 0.20 0.50 – 0.75 (.0256) 0.05 – 0.15 (.0035 – .0079) (.020 – .030) BSC (.002 – .006) 0.195 – 0.30 (.0077 – .0118) FE28 (EB) TSSOP 0204 TYP NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 4. RECOMMENDED MINIMUM PCB METAL SIZE 2. DIMENSIONS ARE INMILLIMETERS FOR EXPOSED PAD ATTACHMENT (INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH 3. DRAWING NOT TO SCALE SHALL NOT EXCEED 0.150mm (.006") PER SIDE 3496ff 

LT3496 package Description UFD Package 28-Lead Plastic QFN (4mm × 5mm) (Reference LTC DWG # 05-08-1712 Rev B) 0.70(cid:112)(cid:0)0.05 4.50(cid:112) 0.05 3.10(cid:112) 0.05 2.50 REF 2.65(cid:112) 0.05 3.65(cid:112) 0.05 PACKAGE OUTLINE 0.25(cid:112)(cid:0)0.05 0.50 BSC 3.50 REF 4.10(cid:112) 0.05 5.50(cid:112) 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED PIN 1 NOTCH 2.50 REF R = 0.20 OR 0.35 4.00(cid:112) 0.10 0.75(cid:112) 0.05 R =TY 0P.05 RTY =P 0.115 (cid:115) 45(cid:111) CHAMFER (2 SIDES) 27 28 0.40(cid:112) 0.10 PIN 1 TOP MARK (NOTE 6) 1 2 5.00(cid:112) 0.10 3.50 REF (2 SIDES) 3.65(cid:112) 0.10 2.65(cid:112) 0.10 (UFD28) QFN 0506 REV B 0.200 REF 0.25(cid:112) 0.05 0.00 – 0.05 0.50 BSC BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220 VARIATION (WXXX-X). 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 3496ff 

LT3496 revision history (Revision history begins at Rev F) REV DATE DESCRIPTION PAGE NUMBER F 4/10 Added H-Grade and Revised Entire Data Sheet 1 through 20 3496ff Information furnished by Linear Technology Corporation is believed to be accurate and reliable.  However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

LT3496 typical application Triple Buck-Boost Mode 100mA × 6 LED Driver PVIN 10V TO 16V C1 2.2µF 100mA 6 LEDs 100mA 6 LEDs 100mA 6 LEDs 3000:1 PWM Dimming at 120Hz L1 L2 L3 10µH 10µH 10µH PWM TG1 M1 TG2 M2 TG3 M3 5V/DIV 3.9M 3.9M 3.9M LED1 LED2 LED3 OVP1 OVP2 OVP3 1Ω 1Ω 1Ω CAP1 100k CAP2 100k CAP3 100k 0.5A/DIIVL D1 D2 D3 C2 C3 C4 C5 C6 C7 ILED 0.1A/DIV 0.1µF 1µF 0.1µF 1µF 0.1µF 1µF PVIN PVIN PVIN SW1 SW2 SW3 0.5µs/DIV 3496 TA06b TG1, TG2, TG3 CAP1, CAP2, CAP3 OVP1, OVP2, OVP3 3V TO 1V6IVN LVEIND1, LED2, LED3 LT3496 VC1, VC2,V VRCE3F 10k 1Cµ8F SPHWDMN PSWHDMN1, PWM2, PWM3 GND CTRL1, CTRL2, CTfRALD3J 470pF 3496 TA06 C1: MURATA GRM31MR71E225KA93 C2, C4, C6: MURATA GRM21BR71H104KA01B C3, C5, C7: MURATA GRM31MR71H105KA88 C8: MURATA GRM31MR71E105KA93 D1-D3: DIODES DFLS160 L1-L3: TAIYO YUDEN NP04SZB 100M M1-M3: ZETEX ZXMP6A13F relateD parts PART NUMBER DESCRIPTION COMMENTS LT1618 Constant Current, 1.4MHz, 1.5A Boost Converter V : 1.6V to 18V, V = 36V, I = 1.8mA, I < 1µA, IN OUT(MAX) Q SD 10-Pin MS Package LT3453 1MHz, 800mA Synchronous Buck-Boost High Power V : 2.7V to 5.5V, V = 5.5V, I = 2.5mA, I < 6µA, IN OUT(MAX) Q SD LED Driver QFN Package LT3466 Dual Constant Current, 2MHz, High Efficiency White LED V : 2.7V to 24V, V = 40V, I = 5mA, I < 16µA, DFN Package IN OUT(MAX) Q SD Boost Regulator with Integrated Schottky Diode LT3467/LT3467A 1.1A (ISW), 1.3MHz/2.1MHz, High Efficiency Step-Up V : 2.4V to 16V, V = 40V, I = 1.2mA, I < 1µA, IN OUT(MAX) Q SD DC/DC Converters with Integrated Soft-Start ThinSOT™ Package LT3474 Step-Down 1A 2MHz LED Driver V : 4V to 36V, V = 15V, I = 2.6mA, I < 1µA, IN OUT(MAX) Q SD TSSOP Package LT3475 Dual Step-Down 1.5A, 2mV LED Driver V : 4V to 36V, I = 6mA, I < 1µA, 20-Lead TSSOPE Package IN Q SD LT3476 High Current 2MHz Quad 1.5A Output LED Driver V : 2.8V to 16V, V = 33.5V, I = 5.5mA, I < 1µA, IN OUT(MAX) Q SD 38-Lead 5mm × 7mm QFN Package LT3477 3A, 42V, 3MHz Step-Up Regulator with Dual Rail-to-Rail V : 2.5V to 2.5V, V = 40V, I = 5mA, I < 1µA, QFN, 16-Pin IN OUT(MAX) Q SD Current Sense TSSOPE Packages LT3478/LT3478-1 4.5A, 2.25MHz LED Driver with 3000:1 Ture Color PWM™ V : 2.8V to 36V, V = 40V, I = 6.1mA, I < 3µA, 16-Pin IN OUT(MAX) Q SD Dimming TSSOPE Package LT3479 3A, Full-Featured DC/DC Converter with Soft-Start and V : 2.5V to 24V, V = 40V, I = 6.5mA, I < 1µA, IN OUT(MAX) Q SD Inrush Current Protection DFN, TSSOP Packages 3496ff 0 Linear Technology Corporation LT 0510 REV F • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 l FAX: (408) 434-0507 l www.linear.com  LINEAR TECHNOLOGY CORPORATION 2007