LT3486 AOT3218 LT3486E LT3486I 16-LEAD LT3486EDHC LT3486EFE 3486EFE LT3486IFE

Dual 1.3A White LED Step-Up Converters with Wide Dimming Description Features Wide (1000:1) PWM Dimming Range with No ColorShift

LT3486 LT3486 Dual 1.3A White LED Step-Up Converters with Wide Dimming Description Features Wide (1000:1) PWM Dimming Range with No ColorShift n Independent Dimming and Shutdown Control of the LED Drivers n Drives Up to 16 White LEDs at 25mA (8 per Driver) from a Single Li-Ion Cell n Drives Up to 16 White LEDs at 100mA (8 per Driver) from 12V Supply n ±3% LED Current Programming Accuracy n Open LED Protection: 36V Clamp Voltage n Fixed Frequency Operation: Up to 2.5MHz n Wide Input Voltage Range: 2.5V to 24V n Low Shutdown Current: ICC < 1µA n Overtemperature Protection n Available in (5mm × 3mm × 0.75mm) 16-Pin DFN and 16-Pin Thermally Enhanced TSSOP Packages n Applications The LT ®3486 is a dual step-up DC/DC converter specifically designed to drive up to 16 White LEDs (8 in series per converter) at constant current from a single Li-Ion cell. Series connection of the LEDs provides identical LED currents resulting in uniform brightness. The two independent converters are capable of driving asymmetric LED strings. The dimming of the two LED strings can be controlled independently via the respective CTRL pins. An internal dimming system allows the dimming range to be extended up to 1000:1 by feeding a PWM signal to the respective PWM pins. The LT3486 LT3486 operating frequency can be set with an external resistor over a 200kHz to 2.5MHz range. A low 200mV feedback voltage (±3% accuracy) minimizes power loss in the current setting resistor for better efficiency. Additional features include output voltage limiting when LEDs are disconnected and overtemperature protection. The LT3486 LT3486 is available in a space saving 16-pin DFN (5mm × 3mm × 0.75mm) and 16-pin thermally enhanced TSSOP packages. Notebook PC Display n LED Camera Light for Cell Phones n Car Dashboard Lighting n Avionics Displays n L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Typical Application Li-Ion Powered Driver for Camera Flash and LCD Backlighting VIN 3V TO 4.2V Efficiency vs VIN 10µF SW1 LED1 AOT3218 AOT3218 L2 10µH SW2 VIN CTRL1 CTRL2 SHDN OFF ON REF LT3486 LT3486 RFB1 0.62 0.1µF GND RT 75 VC2 63.4k 0.1µF FLASH MODE ILED1 = 320mA 80 70 FB2 FB1 VC1 DIMMING 2 PWM2 PWM1 OFF ON 25mA MOVIE MODE ILED1 = 175mA 85 8 LEDs OVP2 OVP1 DIMMING 1 100k 2.2µF EFFICIENCY (%) L1 10µH 2.2µF 90 2.8k 4.7nF RFB2 8.06 3486 TA01a 65 8 LEDS/25mA 3 3.2 3.4 3.6 VIN (V) 3.8 4 4.2 3486 TA01b 3486fd LT3486 LT3486 Absolute Maximum Ratings (Note 1) Input Voltage (VIN). 25V SHDN Voltage. 25V SW1, SW2 Voltages . 40V OVP1, OVP2 Voltages. 40V CTRL1, CTRL2 Voltages. 10V PWM1, PWM2 Voltages. . 10V . FB1, FB2 Voltages. 10V Operating Junction Temperature Range (Note 2) LT3486E LT3486E.40°C to 85°C LT3486I LT3486I.40°C to 125°C Storage Temperature Range DFN .65°C to 125°C TSSOP.65°C to 150°C Maximum Junction Temperature. 125°C Lead Temperature (Soldering, 10 sec, TSSOP). 300°C pin configuration TOP VIEW TOP VIEW SW1 1 16 SW2 VIN 2 15 REF OVP1 3 14 OVP2 RT 4 VC1 5 12 VC2 FB1 6 11 FB2 CTRL1 7 10 CTRL2 PWM1 8 9 17 SW1 1 16 SW2 VIN 2 15 REF OVP1 3 13 SHDN RT 4 14 OVP2 17 13 SHDN VC1 5 12 VC2 FB1 6 11 FB2 CTRL1 7 10 CTRL2 PWM1 8 PWM2 9 PWM2 DHC PACKAGE 16-LEAD 16-LEAD (5mm 3mm) PLASTIC DFN EXPOSED PAD (PIN 17) IS GND MUST BE SOLDERED TO PCB FE PACKAGE 16-LEAD 16-LEAD PLASTIC TSSOP EXPOSED PAD IS GND (PIN 17) MUST BE SOLDERED TO PCB TJMAX = 125°C, JA = 43°C/W, JC = 4°C/W TJMAX = 125°C, JA = 38°C/W, JC = 10°C/W order information LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3486EDHC LT3486EDHC#PBF LT3486EDHC LT3486EDHC#TRPBF 3486 16-Lead (5mm × 3mm) Plastic DFN 40°C to 85°C LT3486EFE LT3486EFE#PBF LT3486EFE LT3486EFE#TRPBF 3486EFE 3486EFE 16-Lead Plastic TSSOP 40°C to 85°C LT3486IFE LT3486IFE#PBF LT3486IFE LT3486IFE#TRPBF 3486IFE 3486IFE 16-Lead Plastic TSSOP 40°C to 125°C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3486EDHC LT3486EDHC LT3486EDHC LT3486EDHC#TR 3486 16-Lead (5mm × 3mm) Plastic DFN 40°C to 85°C LT3486EFE LT3486EFE LT3486EFE LT3486EFE#TR 3486EFE 3486EFE 16-Lead Plastic TSSOP 40°C to 85°C LT3486IFE LT3486IFE LT3486IFE LT3486IFE#TR 3486IFE 3486IFE 16-Lead Plastic TSSOP 40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. 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/ 3486fd LT3486 LT3486 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3V, VCTRL1 = 3V, VCTRL2 = 3V, VPWM1 = 3V, VPWM2 = 3V, VSHDN = 3V, unless otherwise noted. PARAMETER CONDITIONS MIN Minimum Operating Voltage TYP MAX UNITS 2.5 V Maximum Operating Voltage 24 Feedback Voltage (FB1, FB2) l 194 200 V 206 mV Offset between FB1 and FB2 VOS = |FB1-FB2| 0 3 6 mV Feedback Pin Bias Current (FB1, FB2) VFB1 = VFB2 = 0.2V (Note 3) 10 45 100 nA Quiescent Current VFB1 = VFB2 = 1V SHDN = 0V, CTRL1 = CTRL2 = 0V 9 0.1 14 1 mA µA Switching Frequency RT = 53.6k RT = 20.5k 1 2.2 1.25 2.7 MHz MHz 2500 kHz Oscillator Frequency Range (Typical Value) (Note 4) Nominal RT Pin Voltage RT = 53.6k RT = 20.5k RT = 309k 0.75 1.7 RT = 53.6k Maximum Duty Cycle l 200 0.54 Switch Current Limit (SW1, SW2) Switch VCESAT 90 96 90 98 % % % 1 l V 1.3 ISW1 = ISW2 = 0.75A 1.6 300 Switch Leakage Current VSW1 = VSW2 = 10V 0.1 Error Amplifier Transconductance I = ±5µA A mV 220 5 µA µA/V Error Amplifier Voltage Gain 120 VC1, VC2 Switching Threshold 0.85 V VC1, VC2 Clamp Voltage 1.5 V VC1, VC2 Source Current VFB1 = VFB2 = 0V 25 µA VC1, VC2 Sink Current VFB1 = VFB2 = 1V 25 µA VC1, VC2 Pin Leakage Current VC1 = VC2 = 1V, VPWM1 = VPWM2 = 0V 1 OVP1, OVP2 Overvoltage Threshold Voltage 34 CTRL1, CTRL2 Voltages to Turn Off LED1, 2 Currents 35 10 nA 36 V 75 l mV CTRL1, CTRL2 Voltages to Turn On LED1, 2 Currents 150 mV CTRL1, CTRL2 Voltages for Full LED1, 2 Currents 1.8 V l 20 PWM1, PWM2 Voltage High l 0.9 PWM1, PWM2 Voltage Low l CTRL1, CTRL2 Pin Bias Current PWM1, PWM2 Pin Bias Current VCTRL1 = VCTRL2 = 3V µA V 1 µA V 0.1 SHDN Voltage High 40 0.4 VPWM1 = VPWM2 = 3V 30 1.6 V SHDN Voltage Low 0.4 SHDN Pin Bias Current VSHDN = 3V REF Voltage IREF = 10µA REF Source Current Note 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 lifetime. Note 2: The LT3486E LT3486E is guaranteed to meet specified performance from 0°C to 85°C and is designed, characterized and expected to meet 20 1.2 l 1.25 50 80 V µA 1.3 V µA these extended temperature limits, but is not tested at 40°C and 85°C. The LT3486I LT3486I specifications are guaranteed over the 40°C to 125°C temperature range. Note 3: Current flows out of the pin. Note 4: Guaranteed by design and test correlation, not production tested. 3486fd LT3486 LT3486 Typical Performance Characteristics Switching Waveforms PWM Dimming Wavforms ILED 200mA/DIV VSW2 50V/DIV IL2 500mA/DIV IL 500mA/DIV VSW1 10V/DIV IL1 1A/DIV PWM 5V/DIV LED Current vs PWM Duty Cycle Wide Dimming Range (1000:1) 250 1 0.1 1 10 0.1 PWM DUTY CYCLE (%) ± 5mV 200 150 100 50 0 100 250 VIN = 3.6V TA = 25°C FEEDBACK VOLTAGE (mV) FEEDBACK VOLTAGE (mV) 1 0.5 1.5 CONTROL VOLTAGE (V) 0 3486 G01 37 VIN = 3.6V TA = 50°C 100 TA = 25°C 80 TA = 100°C OUTPUT CLAMP VOLTAGE (V) SHDN PIN BIAS CURRENT (µA) 100 50 60 40 1 0.5 1.5 CONTROL VOLTAGE (V) 0 Open-Circuit Output Clamp Voltage vs VIN 37 VIN = 3.6V RT = 63.4k 36 2 3486 G04 Open-Circuit Output Clamp Voltage vs Temperature 120 TA = 25°C TA = 50°C 150 3486 G03 SHDN Pin Bias Current (CTRL1 = CTRL2 = 3V) 140 TA = 85°C 200 0 2 OUTPUT CLAMP VOLTAGE (V) ILED (mA) 10 0.01 0.01 VFB vs VCTRL (Temperature Variation) VFB vs VCTRL VIN = 12V 8/8 LEDs PWM FREQ = 100Hz 3486 G18 VIN = 12V 0.2ms/DIV 8/8 LEDs PWM FREQ = 1kHz 3486 G17 0.5µs/DIV VIN = 3.6V 8 LEDs/25mA 2 LEDs/320mA CIRCUIT OF FRONT PAGE APPLICATION 100 TA = 25°C unless otherwise specified. VOUT2 VOUT1 35 34 VIN = 3.6V RT = 63.4k 36 VOUT1 VOUT2 35 34 20 0 0 4 16 12 8 SHDN PIN VOLTAGE (V) 20 24 3486 G05 33 50 25 75 0 25 50 TEMPERATURE (°C) 100 125 3486 G06 33 2 4 6 8 10 12 14 16 18 20 22 24 VIN (V) 3486 G07 3486fd LT3486 LT3486 Typical Performance Characteristics TA = 25°C RT = 63.4k 1000 RT vs Oscillator Frequency Oscillator Frequency vs VIN 1100 15 RT (k) INPUT CURRENT (mA) 20 OSCILLATOR FREQUENCY (kHz) Input Current with Output 1 and Output 2 Open Circuit TA = 25°C unless otherwise specified. 10 100 5 0 4 2 6 10 8 10 12 14 16 18 20 22 24 VIN (V) 0 500 1000 1500 2000 OSCILLATOR FREQUENCY (kHz) Oscillator Frequency vs Temperature 900 2500 RT = 309k 25 100 8 6 4 0 125 VIN = 3.6V 1300 SHDN = 3V CTRL1 = CTRL2 = 3V 2 0 4 6 PWM 1 0.5 0 40 50 60 70 80 DUTY CYCLE (%) 90 100 3486 G14 10 REF Voltage Load Regulation VIN = 3.6V TA = 50°C 1.25 1.20 REF VOLTAGE (V) REF VOLTAGE (V) 30 6 8 4 PWM PIN VOLTAGE (V) 3486 G13 1.26 1.24 TA = 85°C 1.15 TA = 25°C 1.10 1.05 1.00 0.95 20 2 1.30 1.22 900 PWM 2 0 1.0 8 10 12 14 16 18 20 22 24 VIN (V) 1.28 1000 VIN = 3.6V 0.5 REF Voltage vs Temperature 1.30 1100 8 10 12 14 16 18 20 22 24 VIN (V) 3486 G12 Switch Current Limit vs Duty Cycle 1200 6 UVLO 3486 G11 1400 4 PWM Pin Input Bias Current 1.0 2 0 25 50 75 TEMPERATURE (°C) 2 3486 G10 PWM PIN CURRENT (µA) QUIESCENT CURRENT (mA) OSCILLATOR FREQUENCY (kHz) RT = 53.6k 1000 950 Quiescent Current vs VIN 10 100 50 CURRENT LIMIT (mA) 1000 12 10000 800 1050 3486 G09 3486 G08 RT = 22.1k RT = 53.6k 1.20 50 25 50 0 75 25 TEMPERATURE (°C) 100 125 0.90 VIN = 3.6V TA = 25°C 0 20 40 60 80 100 120 140 160 180 200 REF LOAD CURRENT (µA) 3468 G16 3486 G15 3486fd LT3486 LT3486 Pin Functions SW1, SW2 (Pins 1, 16): The SW Pins are the Collectors of the Internal Power Transistors. Connect the inductors and Schottky diodes to these pins. Minimize trace area at these pins to minimize EMI. VIN (Pin 2): Input Supply Pin. Must be locally bypassed with an X5R or X7R type ceramic capacitor. OVP1, OVP2 (Pins 3, 14): Output Overvoltage Protection Pins. Connect these pins to the output capacitors. The on-chip voltage detectors monitor the voltages at these pins and limit it to 36V (typ) by turning off the respective switcher and pulling its VC pin low. RT (Pin 4): Timing Resistor to Program the Switching Frequency. The switching frequency can be programmed from 200kHz to 2.5MHz. VC1, VC2 (Pins 5, 12): The VC Pins are the Outputs of the Internal Error Amplifier. The voltages at these pins control the peak switch currents. Connect a resistor and capacitor compensation network from these pin to ground. FB1, FB2 (Pins 6, 11): The LT3486 LT3486 regulates the voltage at each feedback pin to 200mV. Connect the cathode of the lowest LED in the string and the feedback resistor (RFB) to the respective feedback pin. The LED current in each string can be programmed by: ILED @ 200mV/RFB, when VCTRL > 1.8V ILED @ VCTRL/(5RFB), when VCTRL < 1V CTRL1, CTRL2 (Pins 7, 10): The CTRL pins are used to provide dimming and shutdown control for the individual switching converters. Connecting these to ground shuts down the respective converter. As the voltages on these pins is ramped from 0V to 1.8V, the LED current in each converter ramps from 0 to ILED = (200mV/RFB). Any voltage above 1.8V does not affect the LED current. PWM1, PWM2 (Pins 8, 9): The PWM control pins can be used to extend the dimming range for the individual switching converter. The LED current in each string can be controlled down to µA levels by feeding a PWM signal to these pins. When the PWM pin voltage is taken below 0.4V, the respective converter is turned off and its VC pin is disconnected from the internal circuitry. Taking it higher than 0.9V resumes normal operation. Connect these pins to 0.9V supply or higher, if not in use. SHDN (Pin 13): Shutdown Pin for the Device. Connect it to 1.6V or higher to enable device; 0.4V or less to disable device. REF (Pin 15): The internal bandgap reference (1.25V) is available at this pin. Bypass with a 0.1µF X5R or X7R ceramic capacitor. Draw no more than 50µA from this pin. Exposed Pad (Pin 17): Ground. The exposed pad of the package provides an electrical contact to ground and good thermal connection to the printed circuit board (PCB). Solder the exposed pad to the PCB system ground. 3486fd LT3486 LT3486 Block Diagram RT VIN 4 SW1 1 2 SW2 16 14 OVP2 OVP1 3 OVERVOLT DETECTION OV1 EN1 CONVERTER1 OVERVOLT DETECTION CONVERTER2 OSC Q1 OSC A3 + + + 0.2V + + EN1 8 REF 1.25V 0.2V + + A2 EA VC1 5 A1 12 VC2 7 80k START-UP CONTROL 20k OV2 EN2 SHDN PWM1 CTRL1 PWM COMP + EA A1 CONVERTER1 CONTROL OSC RSNS2 A2 OV1 EN2 + A3 RSNS1 PWM COMP PWM LOGIC Q2 RAMP GEN + OV2 DRIVER OSC PWM LOGIC 20k 6 13 15 11 FB1 SHDN REF FB2 80k CONVERTER 2 CONTROL 10 9 CTRL2 PWM2 17 3486 F01 EXPOSED PAD Figure 1. LT3486 LT3486 Block Diagram 3486fd LT3486 LT3486 Operation Main Control Loop The LT3486 LT3486 uses a constant frequency, current mode control scheme to provide excellent line and load regulation. It incorporates two identical, but fully independent PWM converters. Operation can be best understood by referring to the block diagram in Figure 1. The oscillator, start-up bias and the bandgap reference are shared between the two converters. The control circuitry, power switch, dimming control etc., are all identical for both converters. At power-up, the output capacitors of both converters are charged up to VIN (input supply voltage) via their respective inductor and the Schottky diode. If the SHDN pin is taken above 1.6V, the bandgap reference, start-up bias and the oscillator are turned on. Grounding the SHDN pin shuts down the part. The CTRL1 and CTRL2 pins perform independent dimming and shutdown control for the two converters. Taking the CTRL pins high, enables the respective converters. Connecting these pins to ground, shuts down each converter by pulling their respective VC pin low. Working of the main control loop can be understood by following the operation of converter 1. At the start of each oscillator cycle, the power switch Q1 is turned on. A voltage proportional to the switch current is added to a stabilizing ramp and the resulting sum is fed into the positive terminal of the PWM comparator A2. When this voltage exceeds the level at the negative input of A2, the PWM logic turns off the power switch. The level at the negative input of A2 is set by the error amplifier A1, and is simply an amplified version of the difference between the feedback voltage and the 200mV reference voltage. In this manner, the error amplifier A1 regulates the feedback voltage to 200mV reference voltage. The output of the error amplifier A1 sets the correct peak current level in inductor L1 to keep the output in regulation. The CTRL1 pin voltage is used to adjust the reference voltage. The PWM1, 2 control pins are used to extend the dimming range for the individual converter. The LED current in each string can be controlled down to µA levels by feeding a PWM signal to these pins. Refer to the Applications Information section for more detail. If only one of the converters is turned on, the other converter will stay off and its output will remain charged up to VIN (input supply voltage). Minimum Output Current The LT3486 LT3486 can drive an 8-LED string at 4mA LED current without pulse skipping. As current is further reduced, the device may begin skipping pulses. This will result in some low frequency ripple, although the LED current remains regulated on an average basis down to zero. The photo in Figure 2 shows circuit operation with 8 white LEDs at 4mA current driven from 3.6V supply. Peak inductor current is less than 200mA and the regulator operates in discontinuous mode implying that the inductor current reached zero during the discharge phase. After the inductor current reaches zero, the switch pin exhibits ringing due to the LC tank circuit formed by the inductor in combination with switch and diode capacitance. This ringing is not harmful; far less spectral energy is contained in the ringing than in the switch transitions. The ringing can be damped by application of a 300 resistor across the inductors, although this will degrade efficiency. VOUT2 10mV/DIV VSW2 20V/DIV IL2 200mA/DIV VIN = 3.6V 0.5µs/DIV ILED2 = 4mA (8 LEDs) CIRCUIT OF FRONT PAGE APPLICATION 3486 F02 Figure 2. Switching Waveforms Open-Circuit Protection The LT3486 LT3486 has internal open-circuit protection for both the converters. Connect the overvoltage protection pins (OVP1, OVP2) to the output of the respective converter. When the LEDs are disconnected from the circuit or fail open, the on-chip voltage detectors monitor the voltages at the OVP1 and OVP2 pins and limits these voltages to 36V (typ) by turning off the respective switcher. The converter will then switch at a very low frequency to minimize the input current. Output voltage and input current during 3486fd LT3486 LT3486 Operation output open circuit are shown in the Typical Performance Characteristics graphs. eight LEDs at 25mA. Converter 1 starts switching at a very low frequency, reducing its input current. Figure 3a shows the transient response of switcher 1 with the LEDs disconnected from the output. When the LED1 string is disconnected from the output, the voltage at the feedback pin (FB1) drops to 0V. As a result, the error amplifier charges up the VC node to the clamp voltage level of 1.5V (typ). The converter starts switching at peak current limit and ramps up the output voltage. When the output voltage reaches the OVP clamp voltage level of 36V (typ), the LT3486 LT3486 shuts off the converter by pulling the VC node to ground. The converter then regulates the output voltage at 36V (typ) by switching at a very low frequency. Soft-Start In the event one of the converters has an output opencircuit, its output voltage will be clamped at 36V (typ). However, the other converter will continue functioning properly. The photo in Figure 3b shows circuit operation with converter 1 output open-circuit and converter 2 driving IL1 1A/DIV The LT3486 LT3486 has a separate internal soft-start circuitry for each converter. Soft-start helps to limit the inrush current during start-up. Soft-start is achieved by clamping the output of the error amplifier during the soft-start period. This limits the peak inductor current and ramps up the output voltage in a controlled manner. The converter enters into soft-start mode whenever the respective CTRL pin is pulled from low to high. Figure 4 shows the start-up waveforms with converter 2 driving eight LEDs at 25mA. The filtered input current, as shown in Figure 4, is well controlled. The soft-start circuit is more effective when driving a smaller number of LEDs. Undervoltage Lockout The LT3486 LT3486 has an undervoltage lockout circuit which shuts down both the converters when the input voltage drops below 2.1V (typ). This prevents the converter to operate in an erratic mode when powered from low supply voltages. Overtemperature Protection VOUT1 20V/DIV VC1 2V/DIV VIN = 3.6V CIRCUIT OF FRONT PAGE APPLICATION 100µs/DIV 3486 F03a LED1 DISCONNECTED AT THIS INSTANT Figure 3a. Transient Response of Switcher 1 with LED1 Disconnected from the Output The maximum allowable junction temperature for LT3486 LT3486 is 125°C. In normal operation, the IC's junction temperature should be kept below 125°C at an ambient temperature of 85°C or less. If the junction temperature exceeds 150°C, the internal thermal shutdown circuitry kicks in and turns-off both the converters. The converters will remain off until the die temperature falls below 150°C. IIN 200mA/DIV IL1 1A/DIV VOUT2 10V/DIV VOUT1 1V/DIV AC COUPLED VFB2 200mV/DIV IL2 500mA/DIV CTRL2 5V/DIV VIN = 3.6V 2ms/DIV CIRCUIT OF FRONT PAGE APPLICATION LED1 DISCONNECTED 3486 F03b Figure 3b. Switching Waveforms with Output 1 Open Circuit VIN = 3.6V 0.5ms/DIV 8 LEDs, 25mA CIRCUIT OF FRONT PAGE APPLICATION 3486 F04 Figure 4. Start-Up Waveforms 3486fd LT3486 LT3486 Applications Information Duty Cycle Operating Frequency Selection The duty cycle for a step-up converter is given by: The choice of operating frequency is determined by several factors. There is a trade-off between efficiency and component size. Higher switching frequency allows the use of smaller inductors albeit at the cost of increased switching losses and decreased efficiency. D= VOUT + VD VIN VOUT + VD VCESAT where: VOUT = Output voltage VD = Schottky forward voltage drop VCESAT = Saturation voltage of the switch VIN = Input battery voltage The maximum duty cycle achievable for LT3486 LT3486 is 96% (typ) when running at 1MHz switching frequency. It increases to 98% (typ) when run at 200kHz and drops to 90% (typ) at 2MHz. Always ensure that the converter is not duty-cycle limited when powering the LEDs at a given switching frequency. Another consideration is the maximum duty cycle achievable. In certain applications the converter needs to operate at the maximum duty cycle in order to light up the maximum number of LEDs. The LT3486 LT3486 has a fixed oscillator off-time and a variable on-time. As a result, the maximum duty cycle increases as the switching frequency is decreased. The circuit of Figure 6a is operated with different values of timing resistor (RT). RT is chosen so as to run the converters at 800kHz (RT = 63.4k), 1.25MHz (RT = 39.1k) and 2MHz (RT = 21.5k). The CTRL pins are used to provide dimming for the respective LED strings. The efficiency comparison for different RT values is shown in Figure 6b. Setting the Switching Frequency The LT3486 LT3486 uses a constant frequency architecture that can be programmed over a 200kHz to 2.5MHz range with a single external timing resistor from the RT pin to ground. The nominal voltage on the RT pin is 0.54V, and the current that flows into the timing resistor is used to charge and discharge an internal oscillator capacitor. A graph for selecting the value of RT for a given operating frequency is shown in the Figure 5. 5V CIN 10µF D1 D2 L1 10µH COUT1 2.2µF SW1 COUT2 2.2µF VIN SW2 OVP1 OVP2 CTRL1 25mA CTRL2 OFF ON REF PWM1 1.25V CREF 0.1µF LT3486 LT3486 FB2 FB1 GND VC1 RT (k) 2.8k 8.06 100 25mA PWM2 SHDN REF 1000 L2 10µH 4.7nF RT VC2 RT 2.8k 4.7nF CIN: 10V, X7R COUT1, COUT2: 35V, X5R D1, D2: ZETEX ZHCS400 ZHCS400 L1, L2: TOKO D53LC D53LC TYPE A 8.06 3486 F06a Figure 6a. 5V to 8/8 White LEDs 10 0 500 1000 1500 2000 OSCILLATOR FREQUENCY (kHz) 2500 3486 G09 Figure 5. Timing Resistor (RT) Value 3486fd 10 LT3486 LT3486 Applications Information 90 Several inductors that work well with the LT3486 LT3486 are listed in Table 1. Consult each manufacturer for more detailed information and for their entire selection of related parts. VIN = 5V 8/8 LEDs 80 EFFICIENCY (%) RT = 63.4k 70 Table 1. Recommended Inductors RT = 21.5k MAX DCR () CURRENT RATING (A) LQH55DN150M LQH55DN150M LQH55DN220M LQH55DN220M 15 22 0.150 0.190 1.40 1.20 Murata (814) 237-1431 www.murata.com A915AY-4R7M A915AY-4R7M A915AY-6R8M A915AY-6R8M A915AY-100M A915AY-100M A918CY-100M A918CY-100M A918CY-150M A918CY-150M 4.7 6.8 10 10 15 0.045 0.068 0.090 0.098 0.149 2.49 2.01 1.77 1.22 0.94 Toko (847) 297-0070 www.toko.com CDRH4D28-100 CDRH4D28-100 CDRH5D18-150 CDRH5D18-150 10 15 0.048 0.145 1.30 0.97 Sumida (847) 956-0666 www.sumida.com PART 50 40 30 L (µH) RT = 39.1k 60 0 5 10 15 LED CURRENT (mA) 25 20 3486 F06b Figure 6b. Efficiency Comparison for Different RT Resistors Inductor Selection The choice of the inductor will depend on the selection of switching frequency of LT3486 LT3486. The switching frequency can be programmed from 200kHz to 2.5MHz. Higher switching frequency allows the use of smaller inductors albeit at the cost of increased switching losses. The inductor current ripple (IL), neglecting the drop across the Schottky diode and the switch, is given by: I = VIN(MIN) · (VOUT (MAX) VIN(MIN) ) L VOUT (MAX) · f · L where: L = Inductor VENDOR Capacitor Selection The small size of ceramic capacitors make them ideal for LT3486 LT3486 applications. Use only X5R and X7R types because they retain their capacitance over wider voltage and temperature ranges than other types such as Y5V or Z5U. A 4.7µF or larger input capacitor is sufficient for most applications. Always use a capacitor with sufficient voltage rating. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information on their entire selection of ceramic parts. Table 2. Ceramic Capacitor Manufacturers Taiyo Yuden (408) 573-4150 www.t-yuden.com VIN(MIN) = Minimum input voltage AVX VOUT(MAX) = Maximum output voltage (803) 448-9411 www.avxcorp.com Murata (714) 852-2001 www.murata.com f = Operating frequency The IL is typically set to 20% to 40% of the maximum inductor current. The inductor should have a saturation current rating greater than the peak inductor current required for the application. Also, ensure that the inductor has a low DCR (copper wire resistance) to minimize I2R power losses. Recommended inductor values range from 4.7µH to 22µH. Diode Selection Schottky diodes with their low forward voltage drop and fast reverse recovery, are the ideal choices for LT3486 LT3486 applications. The diode conducts current only during the switch off time. The peak reverse voltage that the diode must withstand is equal to the regulator output voltage. 3486fd 11 LT3486 LT3486 Applications Information The average forward current in normal operation is equal to the output current, and the peak current is equal to the peak inductor current. A Schottky diode rated at 1A is sufficient for most LT3486 LT3486 applications. Some recommended Schottky diodes are listed in Table 3. 200mV ILED1 200mV RFB2 = ILED2 Table 3. Recommended Schottky Diodes Table 4. RFB Value Selection PART NUMBER RFB1 = VR (V) IAVG (A) MANUFACTURER ILED (mA) RFB () MBR0530 MBR0530 MBRM120E MBRM120E 30 20 0.5 1 On Semiconductor www.onsemi.com 5 40.2 ZLLS400 ZLLS400 ZLLS1000 ZLLS1000 ZHCS400 ZHCS400 ZHCS1000 ZHCS1000 40 40 40 40 0.4 1 0.4 1 Zetex www.zetex.com 10 20.0 15 13.3 20 10.0 25 8.06 When the LT3486 LT3486 is set up for PWM dimming operation, choose a Schottky diode with low reverse leakage current. During PWM dimming operation, the output capacitor is required to hold up the charge in the PWM "off" period. A low reverse leakage Schottky helps in that mode of operation. The Zetex ZLLS400 ZLLS400 and ZLLS1000 ZLLS1000 are available in a small surface mount package and are a good fit for this application. MOSFET Selection The power MOSFET used in LT3486 LT3486 applications with wide dimming range requirements should be chosen based on the maximum drain-source voltage. The maximum drain current ID(MAX) and gate-to-source voltages should also be considered when choosing the FET. Choose a MOSFET with maximum VDS (drain source) voltage greater than the output clamp voltage i.e., 36V (typ). Fairchild Semiconductor's FDN5630 FDN5630 (60V, 1.7A Nchannel FET) is a good fit for most LT3486 LT3486 applications. For dimming low current LEDs (~25mA), Fairchild 2N7002 2N7002 is a good alternative. Programming LED Current The current in each LED string can be set independently by the choice of resistors RFB1 and RFB2 respectively (see front page application). The feedback reference is 200mV. In order to have accurate LED current, precision resistors are preferred (1% is recommended). Most low power white LEDs are driven at maximum currents of 15mA to 25mA. The LT3486 LT3486 can be used to power high power LEDs as well. Refer to the Typical Applications for more detail. Dimming Control The dimming of the two LED strings can be controlled independently by modulating the respective CTRL and PWM pins. There are two ways to control the intensity of the LEDs. Adjusting the LED Current Value Controlling the current flowing through the LEDs controls the intensity of the LEDs.This is the easiest way to control the intensity of the LEDs. The LED forward current can be controlled by modulating the DC voltage at the respective CRTL pin. The PWM pins are not in use when appying this scheme. They must be connected to a 0.9V supply or higher. The DC voltage at the CTRL pin can be modulated in two ways. (a) Using a DC Voltage Source For some applications, the preferred method of brightness control is a variable DC voltage fed to the CTRL pins. The CTRL1, CTRL2 pin voltage can be modulated to set the dimming of the respective LED string. As the voltage on the CTRL1, CTRL2 pin increases from 0V to 1.8V, the LED current increases from 0 to ILED. As the CTRL1, CTRL2 pin voltage increases beyond 1.8V, it has no effect on the LED current. 3486fd 12 LT3486 LT3486 Applications Information The LED current can be set by: Pulse-Width Modulation (PWM) ILED (200mV/RFB), when VCTRL > 1.8V Adjusting the forward current flowing in the LEDs changes the intensity of the LEDs, as explained in the previous section. However, a change in forward current also changes the color of the LEDs. The chromaticity of the LEDs changes with the change in forward current. Many applications cannot tolerate any shift in the color of the LEDs. Controlling the intensity of the LEDs via applying a PWM signal allows dimming of the LEDs without changing the color. ILED (VCTRL/5 · RFB), when VCTRL < 1V Feedback voltage variation versus control voltage is given in the Typical Performance Characteristics graphs. (b) Using a Filtered PWM Signal A variable duty cycle PWM can be used to control the brightness of the LED string. The PWM signal is filtered (Figure 7) by an RC network and fed to the CTRL1, CTRL2 pins. Dimming the LEDs via a PWM signal essentially involves turning the LEDs on and off at the PWM frequency. The human eye has a limit of 60 frames per second. By increasing the PWM frequency to say, 80Hz, the eye can be deceived into believing that the pulsed light source is continously on. Additionally by modulating the duty cycle (amount of "on-time"), the intensity of the LEDs can be controlled. The color of the LEDs remains unchanged in this scheme since the LED current value is either zero or a constant value. The corner frequency of R1, C1 should be much lower than the frequency of the PWM signal. R1 needs to be much smaller than the internal impedance in the CTRL pins, which is 100k. LT3486 LT3486 R1 10k PWM 10kHz TYP CTRL1,2 C1 1µF Figure 8(a) shows a 12V to 8/8 white LED driver. The PWM dimming control method requires an external NMOS tied to the cathode of the lowest LED in the string, as shown in 3486 F07 Figure 7. Dimming Control Using a Filtered PWM Signal 12V (TYP) 9V TO 15V L1 10µH COUT1 2.2µF L2 10µH 5V D1 D2 C1 1µF SW1 LUXEON LEDs LXCL-PWF1 CIN 10µF VIN SW2 OVP1 CTRL1 CTRL2 OFF ON SHDN PWM2 RT VC1 100k 2.2nF 100mA 21.5k RFB1 COUT1, COUT2: 35V, X5R OR X7R 2 CIN: 25V, X5R OR X7R C1: 10V, X5R OR X7R CREF: 6.3V, X5R OR X7R 3.65k 2.2nF D1, D2: ZETEX ZLLS1000 ZLLS1000 L1, L2: TOKO D53LC D53LC (TYPE A) Q1, Q2: FAIRCHILD FDN5630 FDN5630 ILED 200mA/DIV IL 500mA/DIV PWM 5V/DIV VC2 22pF 3.65k Q1 CREF 0.1µF FB2 FB1 PWM FREQ 1kHz VIN REF LT3486 LT3486 PWM1 DIMMING INPUT 1 LUXEON LEDs LXCL-PWF1 OVP2 VIN 100mA COUT2 2.2µF Q2 RFB2 2 DIMMING INPUT 2 PWM FREQ? 1kHz 100k VIN = 12V 0.2ms/DIV 8/8 LEDs PWM FREQ = 1kHz 3486 G18 Figure 8b. PWM Dimming Waveforms 3486 TA10a Figure 8a. 12V to 8/8 White LEDs 3486fd 13 LT3486 LT3486 Applications Information the figure. A PWM logic input is applied to the gate of the NMOS and the PWM pin of the LT3486 LT3486. When the PWM input is taken high, the LEDs are connected to the RFB resistor and a current ILED = 200mV/RFB flows through the LEDs. When the PWM input is taken low, the LEDs are disconnected and turn off. The low PWM input applied to the LT3486 LT3486 ensures that the respective converter turns off and its VC pin goes high impedance. This ensures that the capacitor connected to the VC pin retains its voltage which in turn allows the LEDs to turn on faster, as shown in Figure 8(b). The CTRL pin is not used to modulate the LED current in the scheme. It can be connected to a supply voltage greater than 1.8V. The dimming control pins (PWM1, PWM2) can be used to extend the dimming range for the individual switching converters. The LED current can be controlled down to µA levels by feeding a PWM signal with frequencies in the range of 80Hz to 50kHz. The LED current can be controlled by PWM frequencies above 50kHz but the controllable current decreases with increasing frequency. Pulling the PWM pins below 0.4V disables the respective switcher. Taking it higher than 0.9V resumes normal operation. Connect these pins to 0.9V or higher if not in use. Figure 9 shows the LED current variation vs PWM duty cycle. The LED current is controlled by applying a PWM of frequency 100Hz, 1kHz and 25kHz to the circuit of Figure 8a. As seen in the curves, the LED string is able to get a wide (1000:1) dimming range with PWM frequency of 100Hz. The dimming range decreases as PWM frequency goes up. Board Layout Consideration As with all switching regulators, careful attention must be paid to the PCB board layout and component placement. To prevent electromagnetic interference (EMI) problems, proper layout of high frequency switching paths is essential. Minimize the length and area of all traces connected to the switching node pins (SW1 and SW2). Keep the feedback pins (FB1 and FB2) away from the switching nodes. The DFN and FE packages both have an exposed paddle that must be connected to the system ground. The ground connection for the feedback resistors should be tied directly to the ground plane and not shared with any other component, except the RT resistor, ensuring a clean, noise-free connection. Recommended component placement for the DFN package is shown in the Figure 10. VIAs TO VIN PLANE VOUT1 VOUT2 OVP1 100 REF RT OVP2 SHDN LED CURRENT (mA) 10 VC1 VIN SW1 1 16 2 17 13 5 0.01 0.01 PWM FREQ = 100Hz PWM FREQ = 1kHz PWM FREQ = 25kHz 1 10 0.1 PWM DUTY CYCLE (%) 100 3486 F09 Figure 9. LED Current Variation vs PWM Duty Cycle LED1 11 7 CTRL1 12 6 0.1 VC2 VIN 14 4 FB1 SW2 15 3 1 10 8 9 CTRL2 LED2 VIN PWM1 VIAs TO VIN PLANE FB2 PWM2 3486 F10 VIAs TO GROUND PLANE Figure 10. Recommended Layout for LT3486 LT3486 3486fd 14 LT3486 LT3486 Typical Applications Li-Ion Cell Powered Driver for Camera Flash and LCD Backlighting VIN 3V TO 5V CIN 10µF D1 D2 L1 10µH COUT1 2.2µF LED1 AOT3218 AOT3218 SW1 L2 10µH COUT2 2.2µF SW2 VIN OVP1 320mA CTRL1 DIMMING 1 OFF ON OVP2 CTRL2 SHDN LT3486 LT3486 OFF ON RT VC1 Q1 2.8k 4.7nF 0.1µF RFB2 8.06 3486 TA02a CIN: 6.3V, X5R OR X7R DIELECTRIC COUT1, COUT2: 35V, X5R OR X7R D1: ZETEX ZHCS1000 ZHCS1000 D2: ZETEX ZHCS400 ZHCS400 L1, L2: TOKO D53LC D53LC (TYPE A) Q1: FAIRCHILD FDN5630 FDN5630 Efficiency vs VIN 90 MOVIE MODE ILED1 = 175mA 85 EFFICIENCY (%) 100k CREF 0.1µF VC2 63.4k RFB1 0.62 25mA FB2 FB1 0V REF PWM2 PWM1 5V DIMMING 2 FLASH MODE ILED1 = 320mA 80 75 70 65 8 LEDS/25mA 3 3.2 3.4 3.6 VIN (V) 3.8 4 4.2 3486 TA01b 3486fd 15 LT3486 LT3486 Typical Applications 1 Li-Ion Cell to 8/8 White LEDs 3V TO 5V CIN 10µF D1 D2 L1 10µH COUT1 2.2µF SW1 8 LEDs L2 10µH VIN COUT2 2.2µF SW2 OVP1 VIN CTRL2 OFF ON 25mA CTRL1 SHDN LT3486 LT3486 RT VC1 2.8k 100k 4.7nF Q1 CREF 0.1µF 25mA VC2 2.8k 63.4k COUT1, COUT2: 35V, X5R OR X7R CIN: 10V, X5R OR X7R 8.06 REF FB2 FB1 PWM1 100Hz VIN PWM2 PWM1 5V 8 LEDs OVP2 4.7nF PWM2 100Hz Q2 D1, D2: ZETEX ZLLS400 ZLLS400 L1, L2: TOKO D53LC D53LC (TYPE A) Q1, Q2: FAIRCHILD 2N7002 2N7002 8.06 100k 3486 TA05A TA05A Wide (250:1) Dimming Range (LED Current 0.1mA to 25mA) LED Current and Efficiency vs PWM Duty Cycle 80 EFFICIENCY (%) 25 EFFICIENCY 70 20 65 15 LED CURRENT 60 10 55 50 VIN = 3.6V 8/8 LEDs PWM FREQ = 100Hz 30 10 LED CURRENT (mA) 75 100 35 VIN = 3.6V 8/8 LEDs LED CURRENT (mA) 85 1 0.10 5 0 20 40 60 0 100 80 0.01 0.1 PWM DUTY CYCLE (%) 1 10 DUTY CYCLE (%) 100 3486 TA05d 3486 TA05b PWM Dimming Waveforms LED CURRENT 20mA/DIV IL 200mA/DIV PWM 5V/DIV VIN = 3.6V CTRL1 = 3.6V 8 LEDs/25mA PWM FREQ = 100Hz 2ms/DIV 3486 TA05c 3486fd 16 LT3486 LT3486 Typical Applications 5V to 16/16 White LEDs 5V D5 C3 1µF CIN 1µF D3 16 LEDs D6 L1 15µH C1 0.1µF L2 15µH D2 SW1 SW2 VIN OVP1 CTRL1 CTRL2 OFF ON SHDN REF LT3486 LT3486 RT VC1 100k 63.4k 4.7nF Q1 CREF 0.1µF 8.06 CIN: 6.3V, X5R OR X7R COUT1, COUT2: 35V, X5R OR X7R C1-C4: 50V, X5R OR X7R CREF: 6.3V, X5R OR X7R VC2 22pF 4.02k 4.7nF 35 VIN = 5V 16/16 LEDs 80 EFFICIENCY (%) 20 70 15 65 LED CURRENT 60 10 5 55 50 0 20 40 60 80 LED CURRENT (mA) 25 EFFICIENCY 100k D1, D2: ZETEX ZLLS400 ZLLS400 D3-D6: PHILIPS BAV99W BAV99W L1, L2: TOKO D53LC D53LC (TYPE A) Q1, Q2: FAIRCHILD 2N7002 2N7002 3486 TA08a PWM Dimming Waveforms ILED 50mA/DIV 30 75 PWM FREQ 200Hz Q2 8.06 LED Current and Efficiency vs PWM Duty Cycle 85 25mA FB2 FB1 4.02k VIN PWM2 PWM1 PWM FREQ 200Hz COUT2 2.2µF OVP2 VIN 25mA 16 LEDs C2 0.1µF D1 COUT1 2.2µF C4 1µF D4 IL 500mA/DIV PWM 5V/DIV L = 15µH PWM FREQ = 200Hz 1ms/DIV 3486 TA08c 0 100 PWM DUTY CYCLE (%) 3486 TA08b 3486fd 17 LT3486 LT3486 Package Description DHC Package 16-Lead Plastic DFN (5mm × 3mm) (Reference LTC DWG # 05-08-1706) 5.00 0.10 (2 SIDES) R = 0.20 TYP 0.65 0.05 3.50 0.05 1.65 0.05 (2 SIDES) 3.00 0.10 (2 SIDES) PACKAGE OUTLINE 2.20 0.05 9 R = 0.115 TYP 0.40 1.65 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) PIN 1 NOTCH 8 1 0.25 0.05 0.50 BSC 0.75 0.05 0.200 REF 0.25 0.05 0.50 BSC 0.10 16 4.40 0.05 (2 SIDES) (DHC16 DHC16) DFN 1103 4.40 0.10 (2 SIDES) 0.00 0.05 BOTTOM VIEW-EXPOSED PAD RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJED-1) IN JEDEC PACKAGE OUTLINE MO-229 MO-229 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 FE Package 16-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation BB 4.90 5.10* (.193 .201) 3.58 (.141) 3.58 (.141) 16 1514 13 12 1110 6.60 ±0.10 4.50 ±0.10 9 2.94 (.116) 2.94 6.40 (.116) (.252) BSC SEE NOTE 4 0.45 ±0.05 1.05 ±0.10 0.65 BSC 1 2 3 4 5 6 7 8 RECOMMENDED SOLDER PAD LAYOUT 4.30 4.50* (.169 .177) 0.09 0.20 (.0035 .0079) 0.50 0.75 (.020 .030) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE 0.25 REF 1.10 (.0433) MAX 0° 8° 0.65 (.0256) BSC 0.195 0.30 (.0077 .0118) TYP 0.05 0.15 (.002 .006) FE16 (BB) TSSOP 0204 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE 3486fd 18 LT3486 LT3486 Revision History (Revision history begins at Rev D) REV DATE DESCRIPTION D 03/10 Corrected the Part Number in Description Section and Order Information PAGE NUMBER Updated Typical Value for Switching Frequency Parameter in Electrical Characteristics 1, 2 3 3486fd 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 19 LT3486 LT3486 Typical Application 12V to 8/8 White LEDs 12V (TYP) 9V TO 15V L1 10µH COUT1 2.2µF CIN 10µF L2 10µH LED Current and Efficiency vs PWM Duty Cycle 5V D1 COUT2 2.2µF D2 C1 1µF 90 120 EFFICIENCY SW2 VIN OVP1 VIN 100mA CTRL1 CTRL2 OFF ON SHDN REF LT3486 LT3486 RT VC1 100k 2.2nF 100mA 22pF 21.5k RFB1 COUT1, COUT2: 35V, X5R OR X7R 2 CIN: 25V, X5R OR X7R C1: 10V, X5R OR X7R CREF: 6.3V, X5R OR X7R DIMMING INPUT 2 PWM FREQ? 1kHz 100k 3.65k 2.2nF 80 Q2 D1, D2: ZETEX ZLLS1000 ZLLS1000 L1, L2: TOKO D53LC D53LC (TYPE A) Q1, Q2: FAIRCHILD FDN5630 FDN5630 RFB2 2 80 LED CURRENT 75 60 70 40 65 VC2 3.65k Q1 CREF 0.1µF FB2 FB1 PWM FREQ 1kHz VIN PWM2 PWM1 DIMMING INPUT 1 LUXEON LEDs LXCL-PWF1 OVP2 100 60 VIN = 12V 8/8 LEDs 0 20 LED CURRENT (mA) SW1 LUXEON LEDs LXCL-PWF1 EFFICIENCY (%) 85 20 0 100 40 60 80 PWM DUTY CYCLE (%) 3486 TA10b 3486 TA10a Related Parts PART NUMBER DESCRIPTION COMMENTS LT1618 LT1618 Constant Current, Constant Voltage 1.24MHz, High Efficiency Boost Regulator Up to 16 White LEDs, VIN: 1.6V to 18V, VOUT(MAX) = 34V, IQ = 1.8mA, ISD < 1µA, MS Package LT1932 LT1932 Constant Current, 1.2MHz, High Efficiency White LED Boost Regulator Up to 8 White LEDs, VIN: 1V to 10V, VOUT(MAX) = 34V, IQ = 1.2mA, ISD < 1µA, ThinSOTTM Package LT1937 LT1937 Constant Current, 1.2MHz, High Efficiency White LED Boost Regulator Up to 4 White LEDs, VIN: 2.5V to 10V, VOUT(MAX) = 34V, IQ = 1.9mA, ISD < 1µA, ThinSOT, SC70 Packages LTC3200 LTC3200 Low Noise, 2MHz, Regulated Charge Pump White LED Driver MS Package Up to 6 White LEDs, VIN: 2.7V to 4.5V, IQ = 8mA, ISD < 1µA, LTC3200-5 LTC3200-5 Low Noise, 2MHz, Regulated Charge Pump White LED Driver ThinSOT Package Up to 6 White LEDs, VIN: 2.7V to 4.5V, IQ = 8mA, ISD < 1µA, LTC3201 LTC3201 Low Noise, 1.7MHz, Regulated Charge Pump White LED Driver MS Package Up to 6 White LEDs, VIN: 2.7V to 4.5V, IQ = 6.5mA, ISD < 1µA, LTC3202 LTC3202 Low Noise, 1.5MHz, Regulated Charge Pump White LED Driver MS Package Up to 8 White LEDs, VIN: 2.7V to 4.5V, IQ = 5mA, ISD < 1µA, LTC3205 LTC3205 High Efficiency, Multidisplay LED Controller Up to 4 (Main), 2 (Sub) and RGB, VIN: 2.8V to 4.5V, IQ = 50µA, ISD < 1µA, QFN-24 QFN-24 Package LT3465/LT3465A LT3465/LT3465A Constant Current, 1.2MHz/2.7MHz, High Efficiency White LED Boost Regulator with Integrated Schottky Diode Up to Six White LEDs, VIN: 2.7V to 16V, VOUT(MAX) = 34V, IQ = 1.9mA, ISD < 1µA, ThinSOT Package LT3466 LT3466 Dual Full Function White LED Boost Regulator with Integrated Schottky Diode Drives Up to 20 LEDs, VIN: 2.7V to 24V, VOUT(MAX) = 40V, IQ = 5mA, ISD < 16µA, DFN Package 3486fd 20 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com LT 0310 REV D · PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2008