LT3486 Dual 1.3A White LED Step-Up Converters with Wide Dimming U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Wide (1000:1) PWM Dimming Range with No ColorShift Independent Dimming and Shutdown Control of the LED Drivers Drives Up to 16 White LEDs at 25mA (8 per Driver) from a Single Li-Ion Cell Drives Up to 16 White LEDs at 100mA (8 per Driver) from 12V Supply ±3% LED Current Programming Accuracy Open LED Protection: 36V Clamp Voltage Fixed Frequency Operation: Up to 2MHz Wide Input Voltage Range: 2.5V to 24V Low Shutdown Current: ICC < 1µA Overtemperature Protection Available in (5mm × 3mm × 0.75mm) 16-Pin DFN and 16-Pin Thermally Enhanced TSSOP Packages U APPLICATIO S ■ ■ ■ 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 operating frequency can be set with an external resistor over a 200kHz to 2MHz 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 is available in a space saving 16-pin DFN (5mm × 3mm × 0.75mm) and 16-pin thermally enhanced TSSOP packages. Notebook PC Display LED Camera Light for Cell Phones Car Dashboard Lighting Avionics Displays , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Patent Pending. U ■ 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. TYPICAL APPLICATIO Li-Ion Powered Driver for Camera Flash and LCD Backlighting VIN 3V TO 4.2V Efficiency vs VIN 10µF SW1 LED1 AOT3218 L2 10µH OVP2 OVP1 DIMMING 1 CTRL1 CTRL2 OFF ON SHDN REF LT3486 RT VC1 100k 25mA RFB1 0.62Ω 75 70 VC2 63.4k 0.1µF FLASH MODE ILED1 = 320mA 80 0.1µF FB2 FB1 OFF ON DIMMING 2 PWM2 PWM1 85 8 LEDs SW2 VIN MOVIE MODE ILED1 = 175mA 2.2µF EFFICIENCY (%) L1 10µH 2.2µF 90 2.8k 4.7nF RFB2 8.06Ω 3486 TA01a 65 8 LEDS/25mA 3 3.2 3.4 3.6 VIN (V) 3.8 4 4.2 3486 TA01b 3486f 1 LT3486 U W W W ABSOLUTE AXI U RATI GS (Note 1) Input Voltage (VIN) ...................................................25V ⎯S⎯H⎯D⎯N Voltage ..........................................................25V SW1, SW2 Voltages .................................................40V OVP1, OVP2 Voltages ...............................................40V CTRL1, CTRL2 Voltages ...........................................10V PWM1, PWM2 Voltages ...........................................10V FB1, FB2 Voltages .....................................................10V Operating Temperature Range (Note 2) ...–40°C to 85°C Storage Temperature Range DFN ...................................................–65°C to 125°C TSSOP ............................................... –65°C to 150°C Maximum Junction Temperature .......................... 125°C Lead Temperature (Soldering, 10sec, TSSOP) ...... 300°C U W U PACKAGE/ORDER I FOR ATIO SW1 1 16 SW2 VIN 2 15 REF OVP1 14 OVP2 3 RT 4 VC1 5 12 VC2 FB1 6 11 FB2 CTRL1 7 10 CTRL2 PWM1 8 9 17 ORDER PART NUMBER LT3486EDHC 13 SHDN PWM2 DHC PACKAGE 16-LEAD (5mm × 3mm) PLASTIC DFN EXPOSED PAD (PIN 17) IS GND MUST BE SOLDERED TO PCB TJMAX = 125°C, θJA = 43°C/W, θJC = 4°C/W SW1 1 16 SW2 VIN 2 15 REF OVP1 3 RT 4 DHC PART MARKING 3486 ORDER PART NUMBER TOP VIEW LT3486EFE 14 OVP2 17 13 SHDN VC1 5 12 VC2 FB1 6 11 FB2 CTRL1 7 10 CTRL2 PWM1 8 9 PWM2 FE PART MARKING FE PACKAGE 16-LEAD PLASTIC TSSOP EXPOSED PAD IS GND (PIN 17) MUST BE SOLDERED TO PCB 3486EFE TJMAX = 125°C, θJA = 38°C/W, θJC = 10°C/W Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● 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 Minimum Operating Voltage Maximum Operating Voltage Feedback Voltage (FB1, FB2) Offset between FB1 and FB2 Feedback Pin Bias Current (FB1, FB2) Quiescent Current Switching Frequency Oscillator Frequency Range Nominal RT Pin Voltage CONDITIONS MIN TYP MAX UNITS 200 3 45 9 0.1 1 24 206 6 100 14 1 1.25 2000 V V mV mV nA mA µA MHz kHz V 2.5 ● VOS = |FB1-FB2| VFB1 = VFB2 = 0.2V (Note 3) VFB1 = VFB2 = 1V ⎯S⎯H⎯D⎯N = 0V, CTRL1 = CTRL2 = 0V RT = 53.6k (Note 4) RT = 53.6k 194 0 10 0.75 200 0.54 3486f 2 LT3486 ELECTRICAL CHARACTERISTICS The ● 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 Maximum Duty Cycle RT = 53.6k RT = 20.5k RT = 309k Switch Current Limit (SW1, SW2) Switch VCESAT Switch Leakage Current Error Amplifier Transconductance Error Amplifier Voltage Gain VC1, VC2 Switching Threshold VC1, VC2 Clamp Voltage VC1, VC2 Source Current VC1, VC2 Sink Current VC1, VC2 Pin Leakage Current OVP1, OVP2 Overvoltage Threshold Voltage CTRL1, CTRL2 Voltages to Turn Off LED1, 2 Currents CTRL1, CTRL2 Voltages to Turn On LED1, 2 Currents CTRL1, CTRL2 Voltages for Full LED1, 2 Currents CTRL1, CTRL2 Pin Bias Current PWM1, PWM2 Voltage High PWM1, PWM2 Voltage Low PWM1, PWM2 Pin Bias Current SHDN Voltage High SHDN Voltage Low SHDN Pin Bias Current REF Voltage REF Source Current ● MIN TYP 90 96 90 98 1.3 300 0.1 220 120 0.85 1.5 1 ISW1 = ISW2 = 0.75A VSW1 = VSW2 = 10V ∆I = ±5µA VFB1 = VFB2 = 0V VFB1 = VFB2 = 1V VC1 = VC2 = 1V, VPWM1 = VPWM2 = 0V 34 25 25 1 36 ● VCTRL1 = VCTRL2 = 3V ● ● 150 1.8 20 0.9 5 10 38 75 40 0.1 0.4 1 1.6 0.4 VSHDN = 3V IREF = 10µA Note 1: Absolute maximum ratings are those beyond which the life of a device may be impaired. Note 2: The LT3486E is guaranteed to meet specified performance from 0°C to 70°C and is designed, characterized and expected to meet these extended temperature limits, but is not tested at –40°C and 85°C. ● 1.2 50 20 1.25 80 UNITS % % % A mV µA µA/V V V 30 ● VPWM1 = VPWM2 = 3V MAX 1.3 µA µA nA V mV mV V µA V V µA V V µA V µA Note 3: Current flows out of the pin. Note 4: Guaranteed by design and test correlation, not production tested. 3486f 3 LT3486 U W TYPICAL PERFOR A CE 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 0.5µs/DIV VIN = 3.6V 8 LEDs/25mA 2 LEDs/320mA CIRCUIT OF FRONT PAGE APPLICATION LED Current vs PWM Duty Cycle Wide Dimming Range (1000:1) VFB vs VCTRL (Temperature Variation) 250 250 VIN = 12V 8/8 LEDs PWM FREQ = 100Hz FEEDBACK VOLTAGE (mV) VIN = 3.6V TA = 25°C 1 0.1 ± 5mV 200 150 100 1 10 0.1 PWM DUTY CYCLE (%) 0 100 100 2 37 TA = 25°C 80 TA = 100°C OUTPUT CLAMP VOLTAGE (V) VIN = 3.6V 60 40 37 VIN = 3.6V RT = 63.4k VIN = 3.6V RT = 63.4k 36 2 Open-Circuit Output Clamp Voltage vs VIN OUTPUT CLAMP VOLTAGE (V) 140 100 1 0.5 1.5 CONTROL VOLTAGE (V) 0 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) SHDN PIN BIAS CURRENT (µA) 200 0 1 0.5 1.5 CONTROL VOLTAGE (V) 0 3486 G01 TA = 50°C TA = 85°C 50 50 0.01 0.01 3486 G18 VIN = 12V 0.2ms/DIV 8/8 LEDs PWM FREQ = 1kHz VFB vs VCTRL 10 ILED (mA) 3486 G17 FEEDBACK VOLTAGE (mV) 100 TA = 25°C unless otherwise specified. VOUT2 VOUT1 35 34 36 VOUT1 VOUT2 35 34 20 0 0 4 16 12 8 SHDN PIN VOLTAGE (V) 20 24 3486 G05 33 –50 33 –25 75 0 25 50 TEMPERATURE (°C) 100 125 3486 G06 2 4 6 8 10 12 14 16 18 20 22 24 VIN (V) 3486 G07 3486f 4 LT3486 U W TYPICAL PERFOR A CE CHARACTERISTICS Input Current with Output 1 and Output 2 Open Circuit RT vs Oscillator Frequency OSCILLATOR FREQUENCY (kHz) TA = 25°C RT = 63.4k 15 10 100 5 10 0 4 2 6 8 10 12 14 16 18 20 22 24 VIN (V) 500 1000 1500 2000 OSCILLATOR FREQUENCY (kHz) RT = 309k 100 –50 6 4 8 10 12 14 16 18 20 22 24 VIN (V) VIN = 3.6V 0.5 PWM 1 PWM 2 0 –0.5 2 0 25 50 75 TEMPERATURE (°C) 100 125 SHDN = 3V CTRL1 = CTRL2 = 3V 0 2 4 6 –1.0 8 10 12 14 16 18 20 22 24 VIN (V) Switch Current Limit vs Duty Cycle VIN = 3.6V TA = –50°C 1.25 1.28 1.20 REF VOLTAGE (V) REF VOLTAGE (V) 10 1.30 VIN = 3.6V 1700 1400 6 8 4 PWM PIN VOLTAGE (V) REF Voltage Load Regulation REF Voltage vs Temperature 1500 2 3486 G13 1.30 1600 0 3486 G12 3486 G11 1800 6 UVLO 8 0 –25 4 PWM Pin Input Bias Current 1.0 PWM PIN CURRENT (µA) QUIESCENT CURRENT (mA) RT = 53.6k 2 3486 G10 Quiescent Current vs VIN 10 1000 950 2500 12 10000 OSCILLATOR FREQUENCY (kHz) 1000 3486 G09 Oscillator Frequency vs Temperature RT = 22.1k RT = 53.6k 1050 900 0 3486 G08 CURRENT LIMIT (mA) Oscillator Frequency vs VIN 1100 1000 RT (kΩ) INPUT CURRENT (mA) 20 TA = 25°C unless otherwise specified. 1.26 1.24 TA = 85°C 1.15 TA = 25°C 1.10 1.05 1.00 1.22 1300 0.95 1200 20 30 40 50 60 70 80 DUTY CYCLE (%) 90 100 3486 G14 1.20 –50 VIN = 3.6V TA = 25°C 0.90 –25 50 25 0 75 TEMPERATURE (°C) 100 125 0 20 40 60 80 100 120 140 160 180 200 REF LOAD CURRENT (µA) 3468 G16 3486 G15 3486f 5 LT3486 U U U PI FU CTIO S 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 2MHz. 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 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): 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. 3486f 6 LT3486 W BLOCK DIAGRA SW1 1 RT VIN 4 2 SW2 16 14 OVP2 OVP1 3 OVERVOLT DETECTION CONVERTER1 OVERVOLT DETECTION CONVERTER2 OSC OV2 DRIVER OV1 EN1 OSC PWM LOGIC Q1 Q2 RAMP GEN + OSC + + + EA – A1 VC1 5 + – + REF 1.25V EN1 8 0.2V 0.2V + – + – EA 12 VC2 7 PWM1 CTRL1 OV2 EN2 START-UP CONTROL 20k A2 A1 SHDN 80k PWM COMP + A2 CONVERTER1 CONTROL OSC RSNS2 – – OV1 EN2 + A3 A3 RSNS1 PWM COMP 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 Block Diagram 3486f 7 LT3486 U OPERATIO Main Control Loop The 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 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 300Ω 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 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 3486f 8 LT3486 U OPERATIO 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 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 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 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 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 3486f 9 LT3486 U W U U APPLICATIO S I FOR ATIO 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 tradeoff 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 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. Setting the 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 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. The LT3486 uses a constant frequency architecture that can be programmed over a 200kHz to 2MHz 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. D1 D2 L1 10µH COUT1 2.2µF SW1 L2 10µH VIN COUT2 2.2µF SW2 OVP1 OVP2 CTRL1 CTRL2 25mA 1000 25mA OFF ON SHDN REF PWM1 LT3486 CREF 0.1µF FB2 RT 2.8k 8.06Ω 1.25V REF PWM2 FB1 VC1 RT (kΩ) CIN 10µF 5V 4.7nF VC2 RT 2.8k 4.7nF CIN: 10V, X7R COUT1, COUT2: 35V, X5R D1, D2: ZETEX ZHCS400 L1, L2: TOKO D53LC TYPE A 100 8.06Ω 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 3486f 10 LT3486 U U W U APPLICATIO S I FOR ATIO 90 Several inductors that work well with the 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 Table 1. Recommended Inductors 70 RT = 21.5k 50 40 30 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. The switching frequency can be programmed from 200kHz to 2MHz. Higher switching frequency allows the use of smaller inductors albeit at the cost of increased switching losses. The inductor current ripple (ΔIL), neglecting the drop across the Schottky diode and the switch, is given by: ∆IL = PART LQH55DN150M LQH55DN220M L (µH) 15 22 MAX DCR (Ω) 0.150 0.190 CURRENT RATING (A) 1.40 1.20 A915AY-4R7M A915AY-6R8M A915AY-100M A918CY-100M A918CY-150M CDRH4D28-100 CDRH5D18-150 4.7 6.8 10 10 15 10 15 0.045 0.068 0.090 0.098 0.149 0.048 0.145 2.49 2.01 1.77 1.22 0.94 1.30 0.97 RT = 39.1k 60 VIN(MIN) • (VOUT (MAX) – VIN(MIN) ) VOUT (MAX) • f • L where: L = Inductor The small size of ceramic capacitors make them ideal for 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 (803) 448-9411 www.avxcorp.com VOUT(MAX) = Maximum output voltage Murata (714) 852-2001 www.murata.com 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. Sumida (847) 956-0666 www.sumida.com Capacitor Selection f = Operating frequency The ΔIL is typically set to 20% to 40% of the maximum inductor current. VENDOR Murata (814) 237-1431 www.murata.com Toko (847) 297-0070 www.toko.com Diode Selection Schottky diodes with their low forward voltage drop and fast reverse recovery, are the ideal choices for 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. 3486f 11 LT3486 U W U U APPLICATIO S I FOR ATIO 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 applications. Some recommended Schottky diodes are listed in Table 3. Table 3. Recommended Schottky Diodes PART NUMBER 200mV ILED1 200mV RFB2 = ILED2 RFB1 = Table 4. RFB Value Selection VR (V) IAVG (A) MANUFACTURER MBR0530 MBRM120E 30 20 0.5 1 On Semiconductor www.onsemi.com ZLLS400 ZLLS1000 ZHCS400 ZHCS1000 40 40 40 40 0.4 1 0.4 1 Zetex www.zetex.com When the 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 and 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 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 (60V, 1.7A N-channel FET) is a good fit for most LT3486 applications. For dimming low current LEDs (~25mA), Fairchild 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). ILED (mA) 5 10 15 20 25 RFB (Ω) 40.2 20.0 13.3 10.0 8.06 Most low power white LEDs are driven at maximum currents of 15mA to 25mA. The 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. 3486f 12 LT3486 U U W U APPLICATIO S I FOR ATIO 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 100kΩ. 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 OVP2 VIN CTRL1 CTRL2 OFF ON SHDN 100mA PWM2 CREF 0.1µF RT VC1 3.65k PWM 5V/DIV VC2 2.2nF 2.2nF RFB1 COUT1, COUT2: 35V, X5R OR X7R D1, D2: ZETEX ZLLS1000 2Ω CIN: 25V, X5R OR X7R L1, L2: TOKO D53LC (TYPE A) Q1, Q2: FAIRCHILD FDN5630 C1: 10V, X5R OR X7R CREF: 6.3V, X5R OR X7R VIN = 12V 0.2ms/DIV 8/8 LEDs PWM FREQ = 1kHz DIMMING INPUT 2 3.65k 21.5k Q1 IL 500mA/DIV 100mA 22pF DIMMING INPUT 1 ILED 200mA/DIV FB2 FB1 100k LUXEON LEDs LXCL-PWF1 VIN REF LT3486 PWM1 PWM FREQ 1kHz COUT2 2.2µF PWM FREQ 1kHz Q2 RFB2 2Ω 3486 G18 Figure 8b. PWM Dimming Waveforms 100k 3486 TA10a Figure 8a. 12V to 8/8 White LEDs 3486f 13 LT3486 U W U U APPLICATIO S I FOR ATIO the figure. A PWM logic input is applied to the gate of the NMOS and the PWM pin of the 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 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 1 SW1 1 16 2 15 3 14 4 FB1 0.1 0.01 0.01 PWM FREQ = 100Hz PWM FREQ = 1kHz PWM FREQ = 25kHz 1 10 0.1 PWM DUTY CYCLE (%) LED1 CTRL1 100 Figure 9. LED Current Variation vs PWM Duty Cycle VC2 VIN 13 5 12 6 11 7 10 8 9 CTRL2 LED2 VIN PWM1 3486 F09 17 SW2 VIAs TO VIN PLANE FB2 PWM2 3486 F10 VIAs TO GROUND PLANE Figure 10. Recommended Layout for LT3486 3486f 14 LT3486 U TYPICAL APPLICATIO S Li-Ion Cell Powered Driver for Camera Flash and LCD Backlighting VIN 3V TO 5V CIN 10mF D1 D2 L1 10mH COUT1 2.2mF LED1 AOT3218 SW1 L2 10mH COUT2 2.2mF SW2 VIN OVP1 OVP2 CTRL1 CTRL2 25mA 320mA DIMMING 1 OFF ON SHDN LT3486 REF FB2 FB1 Q1 OFF ON RT VC1 0V VC2 63.4k 2.8k 0.1mF 4.7nF RFB2 8.06W 3486 TA02a CIN: 6.3V, X5R OR X7R DIELECTRIC COUT1, COUT2: 35V, X5R OR X7R D1: ZETEX ZHCS1000 D2: ZETEX ZHCS400 L1, L2: TOKO D53LC (TYPE A) Q1: FAIRCHILD FDN5630 Efficiency vs VIN 90 MOVIE MODE ILED1 = 175mA 85 EFFICIENCY (%) 100k RFB1 0.62W CREF 0.1mF 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 3486f 15 LT3486 U TYPICAL APPLICATIO S 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 OVP2 VIN CTRL1 CTRL2 OFF ON SHDN LT3486 RT VC1 2.8k 8.06Ω REF CREF 0.1µF 25mA VC2 2.8k 63.4k 4.7nF Q1 VIN FB2 FB1 5V 8 LEDs PWM2 PWM1 100k SW2 OVP1 25mA PWM1 100Hz COUT2 2.2µF COUT1, COUT2: 35V, X5R OR X7R CIN: 10V, X5R OR X7R 4.7nF PWM2 100Hz Q2 D1, D2: ZETEX ZLLS400 L1, L2: TOKO D53LC (TYPE A) Q1, Q2: FAIRCHILD 2N7002 8.06Ω 100k 3486 TA05A Wide (250:1) Dimming Range (LED Current 0.1mA to 25mA) LED Current and Efficiency vs PWM Duty Cycle 80 EFFICIENCY (%) 70 20 65 15 LED CURRENT 60 10 55 5 50 40 60 10 LED CURRENT (mA) 25 EFFICIENCY 20 VIN = 3.6V 8/8 LEDs PWM FREQ = 100Hz 30 75 0 100 35 VIN = 3.6V 8/8 LEDs LED CURRENT (mA) 85 0.10 0 100 80 1 0.01 0.1 PWM DUTY CYCLE (%) 3486 TA05b 1 10 DUTY CYCLE (%) 100 3486 TA05d 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 3486f 16 LT3486 U TYPICAL APPLICATIO S 5V to 16/16 White LEDs 5V D5 C3 1mF D6 CIN 1mF D3 C4 1mF D4 16 LEDs SW2 VIN OVP1 OVP2 VIN CTRL1 CTRL2 OFF ON SHDN FB2 RT VC1 100k 63.4k 4.7nF Q1 8.06W 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 D1, D2: ZETEX ZLLS400 D3-D6: PHILIPS BAV99W L1, L2: TOKO D53LC (TYPE A) Q1, Q2: FAIRCHILD 2N7002 EFFICIENCY (%) 20 70 15 65 LED CURRENT 60 10 55 5 50 40 60 80 LED CURRENT (mA) 25 EFFICIENCY 20 3486 TA08a PWM Dimming Waveforms ILED 50mA/DIV 30 75 0 100k 35 VIN = 5V 16/16 LEDs 80 PWM FREQ 200Hz Q2 8.06W LED Current and Efficiency vs PWM Duty Cycle 85 25mA CREF 0.1mF PWM2 FB1 4.02k VIN REF LT3486 PWM1 PWM FREQ 200Hz COUT2 2.2mF D2 SW1 16 LEDs C2 0.1mF D1 COUT1 2.2mF 25mA L2 15mH L1 15mH C1 0.1mF IL 500mA/DIV PWM 5V/DIV L = 15µH PWM FREQ = 200Hz 1ms/DIV 3486 TA08c 0 100 PWM DUTY CYCLE (%) 3486 TA08b 3486f 17 LT3486 U PACKAGE DESCRIPTIO DHC Package 16-Lead Plastic DFN (5mm × 3mm) (Reference LTC DWG # 05-08-1706) 0.65 ±0.05 3.50 ±0.05 1.65 ±0.05 2.20 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 4.40 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 5.00 ±0.10 (2 SIDES) R = 0.20 TYP 3.00 ±0.10 (2 SIDES) 9 0.40 ± 0.10 16 1.65 ± 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) PIN 1 NOTCH (DHC16) DFN 1103 8 0.200 REF 1 0.25 ± 0.05 0.50 BSC 0.75 ±0.05 4.40 ±0.10 (2 SIDES) 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJED-1) IN JEDEC PACKAGE OUTLINE 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 3486f 18 LT3486 U PACKAGE DESCRIPTIO 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 9 2.94 (.116) 4.50 ±0.10 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 3486f 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 U TYPICAL APPLICATIO 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 D2 C1 1µF COUT2 2.2µF 90 120 EFFICIENCY 85 OVP1 OVP2 VIN CTRL1 CTRL2 OFF ON SHDN 100mA PWM2 PWM1 RT VC1 100mA VC2 3.65k RFB1 2Ω 75 60 70 40 2.2nF 2.2nF COUT1, COUT2: 35V, X5R OR X7R D1, D2: ZETEX ZLLS1000 L1, L2: TOKO D53LC (TYPE A) CIN: 25V, X5R OR X7R Q1, Q2: FAIRCHILD FDN5630 C1: 10V, X5R OR X7R CREF: 6.3V, X5R OR X7R 60 PWM FREQ 1kHz Q2 RFB2 2Ω 100k 20 VIN = 12V 8/8 LEDs DIMMING INPUT 2 3.65k 21.5k Q1 80 LED CURRENT 65 22pF DIMMING INPUT 1 100k CREF 0.1µF 80 FB2 FB1 PWM FREQ 1kHz VIN REF LT3486 LUXEON LEDs LXCL-PWF1 LED CURRENT (mA) LUXEON LEDs LXCL-PWF1 100 SW2 VIN EFFICIENCY (%) SW1 0 20 40 60 80 PWM DUTY CYCLE (%) 0 100 3486 TA10b 3486 TA10a RELATED PARTS PART NUMBER LT1618 DESCRIPTION Constant Current, Constant Voltage 1.24MHz, High Efficiency Boost Regulator LT1932 Constant Current, 1.2MHz, High Efficiency White LED Boost Regulator LT1937 Constant Current, 1.2MHz, High Efficiency White LED Boost Regulator LTC3200 Low Noise, 2MHz, Regulated Charge Pump White LED Driver MS Package Low Noise, 2MHz, Regulated Charge Pump White LED Driver ThinSOT Package Low Noise, 1.7MHz, Regulated Charge Pump White LED Driver MS Package Low Noise, 1.5MHz, Regulated Charge Pump White LED Driver MS Package High Efficiency, Multidisplay LED Controller LTC3200-5 LTC3201 LTC3202 LTC3205 LT3465/LT3465A Constant Current, 1.2MHz/2.7MHz, High Efficiency White LED Boost Regulator with Integrated Schottky Diode LT3466 Dual Full Function White LED Boost Regulator with Integrated Schottky Diode COMMENTS Up to 16 White LEDs, VIN: 1.6V to 18V, VOUT(MAX) = 34V, IQ = 1.8mA, ISD < 1µA, MS Package Up to 8 White LEDs, VIN: 1V to 10V, VOUT(MAX) = 34V, IQ = 1.2mA, ISD < 1µA, ThinSOTTM Package Up to 4 White LEDs, VIN: 2.5V to 10V, VOUT(MAX) = 34V, IQ = 1.9mA, ISD < 1µA, ThinSOT, SC70 Packages Up to 6 White LEDs, VIN: 2.7V to 4.5V, IQ = 8mA, ISD < 1µA, Up to 6 White LEDs, VIN: 2.7V to 4.5V, IQ = 8mA, ISD < 1µA, Up to 6 White LEDs, VIN: 2.7V to 4.5V, IQ = 6.5mA, ISD < 1µA, Up to 8 White LEDs, VIN: 2.7V to 4.5V, IQ = 5mA, ISD < 1µA, Up to 4 (Main), 2 (Sub) and RGB, VIN: 2.8V to 4.5V, IQ = 50µA, ISD < 1µA, QFN-24 Package Up to Six White LEDs, VIN: 2.7V to 16V, VOUT(MAX) = 34V, IQ = 1.9mA, ISD < 1µA, ThinSOT Package Drives Up to 20 LEDs, VIN: 2.7V to 24V, VOUT(MAX) = 40V, IQ = 5mA, ISD < 16µA, DFN Package 3486f 20 Linear Technology Corporation LT/TP 0705 500 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005