LTC3490 Single Cell 350mA LED Driver U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO 350mA Constant Current Output 2.8V to 4V Output Compliance 1- or 2-Cell NiMH or Alkaline Input Synchronous Rectification: Up to 90% Efficiency Fixed Frequency Operation: 1.3MHz Low Quiescient Current: <1mA Very Low Shutdown Current: <50µA Open LED Output Limited to 4.7V VIN Range: 1V to 3.2V Dimming Control Undervoltage Lockout to Protect Batteries Low Profile (0.75mm) 3mm × 3mm Thermally Enhanced 8-Lead DD and S8 Packages U APPLICATIO S ■ ■ Portable Lighting Rechargeable Flashlights The LTC®3490 provides a constant current drive for 1W LED applications. It is a high efficiency boost converter that operates from 1 or 2 NiMH or alkaline cells and generates 350mA of constant current with up to 4V of compliance. It contains a 100mΩ NFET switch and a 130mΩ PFET synchronous rectifier. The fixed switching frequency is internally set to 1.3MHz. The LTC3490 limits the output voltage to 4.7V if the output load is disconnected. It also features an analog dimming capability that reduces the drive current proportional to the CTRL/SHDN pin voltage. A low-battery logic output signals when the battery has dropped below 1V/cell. An undervoltage lockout circuit shuts down the LTC3490 when the battery voltage drops below 0.85V/cell. The feedback loop is internally compensated to minimize component count. , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. U TYPICAL APPLICATIO Efficiency vs VIN at VLED = 3.5V Single Cell Minimum Component LED Driver 100 3.3µH IOUT = 350mA 90 80 SW ON/OFF 1 NiMH OR ALKALINE CELL LTC3490 + CTRL/SHDN LED CELLS 1M 70 CAP LOBAT GND 350mA 4.7µF HIGH CURRENT LED EFFICIENCY (%) VIN 60 50 40 30 20 10 3490 TA01 0 1 1.5 2 VIN (V) 2.5 3 3490 TA02 3490f 1 LTC3490 W W W AXI U U ABSOLUTE RATI GS (Note 1) Supply Voltage (VIN) ................................... – 0.3V to 6V Input Voltages (CTRL/SHDN, CELLS) ......... – 0.3V to 6V Output Voltages (CAP, LED, SW) ................ – 0.3V to 6V Operating Temperature Range (Note 2) .. – 40°C to 85°C Storage Temperature Range ................. – 65°C to 125°C Lead Temperature (Soldering, 10 sec, S8) .......... 300°C U U W PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW CELLS 1 8 CTRL/SHDN VIN 2 7 LOBAT 6 CAP 5 LED SW 3 9 GND 4 DD PACKAGE 8-LEAD (3mm × 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 43°C/ W (NOTE 4) EXPOSED PAD (PIN 9) IS GND MUST BE SOLDERED TO PCB (NOTE 5) LTC3490EDD ORDER PART NUMBER TOP VIEW CELLS 1 8 CTRL/SHDN VIN 2 7 LOBAT SW 3 6 CAP GND 4 5 LED DD PART MARKING LBRQ LTC3490ES8 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO 3490 TJMAX = 125°C, θJA = 150°C/ W (NOTE 4) Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 2.5V unless otherwise specified. SYMBOL PARAMETER VIN Input Supply Range CONDITIONS VIN(START) Minimum Start-Up Voltage (Note 3) ILED(MAX) LED Drive Current VCTRL/SHDN = VIN, DD Package 25°C to 85°C – 40°C to <25°C VCTRL/SHDN = VIN, S8 Package 25°C to 85°C – 40°C to <25°C MIN TYP MAX UNITS 3.2 V 0.9 1 V 330 310 350 350 370 385 mA mA 337 325 350 345 363 365 mA mA 0.1 1 µA 4 V 1 ILED(SHDN) LED Drive Current in Shutdown VLED Output Compliance Voltage VLED(OVL) Output Voltage Overvoltage Limit Open LED 4.7 V IIN(SHDN) Input Current, Shutdown VCTRL/SHDN = 0V, Excluding Switch Leakage 20 50 µA IIN(ACTIVE) Input Current, Active Excluding Load Power 20 30 mA fSW Switching Frequency 1.3 1.6 MHz IL(NMOS) Leakage Current, NMOS Switch 0.1 RON(NMOS) On Resistance, NMOS Switch 0.1 Ω IL(PMOS) Leakage Current, PMOS Switch 0.1 µA RON(PMOS) On Resistance, PMOS Switch 0.13 Ω VIH Input High (CELLS) VIN • 0.9 V Input High (SHDN) VIL VCTRL/SHDN = 0V ● 2.8 ● 4.2 ● 1.0 VIN – 0.4 V Input Low (CELLS) Input Low (SHDN) µA 0.4 VIN • 0.2 V V 3490f 2 LTC3490 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 2.5V unless otherwise specified. SYMBOL IIN PARAMETER Input Current (CTRL/SHDN, CELLS) CONDITIONS MIN KCTRL Control Gain, ILED/VCTRL Scales Linearity with VIN, VIN = 1V RON(LOBAT) On Resistance, LOBAT Output VIN Below UVLO Threshold ● VIN(LOBAT1) Input Voltage, Low Battery, 1 Cell VCELLS = 0V ● VIN(LOBAT2) Input Voltage, Low Battery, 2 Cells VCELLS = VIN ● VIN(UVLO2) Input Voltage, Undervoltage Lockout, VCELLS = VIN 2 Cells VIN(UVLO1) Input Voltage, Undervoltage Lockout, VCELLS = 0 V 1 Cell TYP 0.01 MAX UNITS µA 500 mA/V 300 Ω 0.8 1.12 V 1.8 2.24 V ● 1.4 1.8 V ● 0.7 0.9 V Note 4: This device includes overtemperature protection intended to protect the device during momentary overload conditions. The maximum junction temperature may be exceeded when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may result in device degradation or failure. Note 5: The Exposed Pad of the DFN package must be soldered to a PCB pad for optimum thermal conductivity. This pad must be connected to ground. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC3490 is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C range are assured by design, characterization and correlation with statistical process controls. Note 3: The LTC3490 input voltage may drop below the minimum start-up voltage once the LED voltage has risen above 2.3V. U W TYPICAL PERFOR A CE CHARACTERISTICS Oscillator Frequency vs Temperature ILED vs VCTRL 1.400 ILED vs VIN 375 400 VLED = 3.5V 350 350 1.360 1.280 250 ILED (mA) 1.320 ILED (mA) FREQUENCY (MHz) 300 MAXIMUM 200 150 325 300 MINIMUM 100 275 1.240 50 1.200 –50 50 0 TEMPERATURE (°C) 100 3490 G01 0 250 0 0.2 0.4 0.6 VCTRL/VIN (V) 0.8 1 3490 G02 1 1.5 2 VIN (V) 2.5 3 3490 G03 3490f 3 LTC3490 U W TYPICAL PERFOR A CE CHARACTERISTICS ILED vs VLED 360 Efficiency vs ILED 100 VIN = 2.4V 358 356 80 EFFICIENCY (%) 354 ILED (mA) VIN = 2.4V 90 352 350 348 50 40 346 30 344 20 342 10 340 VIN = 1.2V 70 60 0 3 2.8 3.2 3.4 3.6 VLED (V) 3.8 4 3490 G04 0 100 200 ILED (mA) 400 300 3490 G05 U U U PI FU CTIO S CELLS (Pin 1): A logic input to set the low-battery and undervoltage shutdown thresholds. A logic low (tied to GND) will set the thresholds for 1 cell. A logic high (tied to VIN) will set the thresholds for 2 cells. VIN (Pin 2): Supply Voltage. SW (Pin 3): Switch Input. Connect this pin to an external inductor from VIN. GND (Pin 4): Circuit Ground. LED (Pin 5): Output Drive Current to LED. CAP (Pin 6): Filter Capacitor. A 4.7µF low ESR capacitor should be tied to this pin. CTRL/SHDN (Pin 8): Analog Control Voltage and Shutdown. When VIN • 0.2 < VCTRL < VIN • 0.9, the LED drive current varies according to the formula: ⎛V ⎞ ILED = 500 • ⎜ CTRL – 0.2⎟ mA ⎝ VIN ⎠ When VCTRL > VIN • 0.9, the LED drive current is clamped at 350mA. When VCTRL < VIN • 0.2, then the part is in low power shutdown. Exposed Pad (Pin 9, DD Package): Ground. This pin must be soldered to the PCB to provide both electrical contact to ground and good thermal contact to the PCB. LOBAT (Pin 7): Low active, open-drain logic output indicating a low-battery condition. 3490f 4 LTC3490 W FU CTIO AL DIAGRA U 3 SW – 2 P BODY CONTROL + VIN CAP 6 GATE CONTROL AND DRIVERS SENSE AMP LIMIT 19.2Ω + – OVERVOLTAGE DETECT LED 5 250k – PWM LOGIC 0.1Ω 40k VREF/2 + OSCILLATOR START-UP – 8 CTRL/ SHDN DIMMING AMP + LOBAT IREF 1 BATTERY MONITOR CELLS 7 SHUTDOWN GND 4 3490 FD 3490f 5 U LTC3490 U OPERATIO The LTC3490 is a high efficiency, constant current source for 1W high intensity white LEDs. These high intensity LEDs require a fixed current of 350mA with a voltage compliance of 2.8V to 4V. The LTC3490 operates with 1 or 2 NiMH or alkaline cells. It functions as a boost converter with a current sense resistor providing the control feedback. If the battery voltage is greater than the required LED compliance, it will cycle off periodically to maintain the correct average current. It features a low voltage start-up circuit that will start with an input voltage of only 1V. Once the drive voltage exceeds 2.3V, the circuit operates from the drive voltage. to the battery voltage. The LED drive current is given by the formula: ⎛V ⎞ ILED = 500 • ⎜ CTRL – 0.2⎟ mA ⎝ VIN ⎠ When VCTRL > VIN • 0.9, the LED drive current is clamped at 350mA. Open-Circuit Protection All of the loop compensation is internal; only the main filter capacitor is needed for stable operation. Since this is a boost converter attempting to drive a current into the load, an open or high impedance load will cause the regulator loop to increase the output voltage in an effort to achieve regulation. To protect the device, maximum output voltage is limited to 4.7V under all conditions. Dimming Function Undervoltage Sense and Protection During normal operation with the CTRL/SHDN pin connected to VIN, the LED drive current is controlled at 350mA. The drive current can be reduced by changing the voltage on the CTRL/SHDN pin. The undervoltage lockout prevents excessive inductor peak current and protects the batteries from deep discharging which can damage them. The low-battery indicator allows the end user to be made aware that the batteries are nearing the end of their useful life. For VIN • 0.2 < VCTRL < VIN • 0.9, the LED current is proportional to VCTRL/VIN. This allows a simple potentiometer from VIN to control the current without sensitivity 3490f 6 LTC3490 U W U U APPLICATIO S I FOR ATIO The LTC3490 requires only four external components to operate: an inductor, an output capacitor, a switch and a pull-down resistor. The inductor is nominally set at 3.3µH and the capacitor at 4.7µF. Optional components include an input capacitor and dimming resistors. where: VIN = Input Voltage (V) VOUT = Output Voltage (V) IOUT = LED Drive Current (A) IIN = Input Current = VOUT/VIN • IOUT (A) COMPONENT SELECTION RP = RDSON of the PFET Switch (Ω) Inductor Selection RN = RDSON of the NFET Switch (Ω) The high frequency operation of the LTC3490 allows the use of small surface mount inductors. The minimum inductance value is proportional to the operating frequency and is limited by the following constraints: 3 L≥ H f and L≥ ( VIN(MIN) • VOUT(MAX) – VIN(MIN) f • Ripple • VOUT(MAX) )H where: f = Operating Frequency (Hz) Ripple = Inductor Current Ripple (A) VIN(MIN) = Minimum Input Voltage (V) VOUT(MAX) = Maximum Output Voltage (V) The inductor current ripple is typically set to 20% to 40% of the inductor current. The peak inductor current is given by: ILPK = IOUT For high efficiency, choose an inductor with a high frequency core material, such as ferrite, to reduce core losses. The inductor should have low ESR (equivalent series resistance) to reduce the I2R losses and must be able to handle the peak inductor current at full load without saturating. In single cell applications, the inductor ESR must be below 25mΩ to keep the efficiency up and maintain output current regulation. Dual cell applications can tolerate significantly higher ESR (up to 75mΩ) with minimal efficiency degradation. Molded chokes or chip inductors usually do not have enough core to support the peak inductor currents in the 1A to 2A region. If radiated noise is an issue, use a toroid, pot core or shielded bobbin inductor to minimize radiated noise. See Table 1 for a list of suggested inductors. Look closely at the manufacturers data sheets; they specify saturation current differently. Table 1. Inductor Information INDUCTOR PART NUMBER ESR (mΩ) SATURATION CURRENT (A) TOKO A918CY-3R3M 47 1.97 TYCO DN4835-3R3M 58 2.15 TDK SLF7045T-3R3M2R5 20 2.5 ( VOUT + IOUT • RP ) – RN • IIN Output Capacitor Selection VIN – RN • IIN VIN ( VOUT – VIN ) + 2 • L • f • VOUT The output capacitor value and equivalent series resistance (ESR) are the primary factors in the output ripple. The output ripple is not a direct concern for LED drive as the LED will operate at the average current value. However the peak pulsed forward current rating of the LED must not be exceeded to avoid damaging the LED. 3490f 7 LTC3490 U W U U APPLICATIO S I FOR ATIO The output ripple voltage has two primary components. The first is due to the value of the capacitor and is given by: VRCAP ILPK • VIN C • VOUT • f The second is due to the capacitor ESR: VRESR = ILPK • RESR Component values will be calculated for 1 or 2 NiMH cells and assumes the end-of-charge voltage to be 0.9V per cell. The operating frequency is assumed to be 1MHz, the worst-case low frequency. The allowed inductor ripple current is 0.31A. Table 3 shows a summary of the key parameters. Table 3. Summary of Key Parameters PARAMETER The LED current ripple and peak pulsed current are calculated by: • VRESR VR IRLED CAP RSENSE + RLED IR IPPFC = IOUT + LED 2 1-CELL 2-CELL UNITS LMIN 2.2 3.2 µH Choose L 3.3 3.3 µH IIN 1.56 0.78 A ILPK 1.93 0.96 A Choose C 4.7 4.7 µF Cap ESR 5 5 mΩ VRCAP 0.09 0.09 V VRESR 0.01 0.005 V IRLED 0.10 0.09 A RSENSE = Internal Sense Resistor = 0.1Ω IPPFC 0.40 0.39 A RLED = Dynamic Impedance of the LED where: where: Low ESR capacitors should be used to minimize output ripple. Ceramic X5R or X7R type capacitors are recommended. See Table 2 for a list of component suppliers. Table 2. Capacitor Information CAPACITOR PART NUMBER DESCRIPTION TDK C2012X5R0J475K 4.7µF, 6.3V, X5R in 0805 AVX 1210ZC475MAT 4.7µF, 10V, X7R in 1210 Taiyo Yuden CELMK316BJ475ML 4.7µF, 10V, X7R in 1206 ILPK is the peak inductor current VRCAP is the ripple voltage due to the output capacitor value VRESR is the ripple voltage due to the output capacitor ESR IRLED is the LED current ripple IPPFC is the LED peak pulsed forward current PC Board Layout Checklist Input Capacitor Selection Most battery-powered applications do not need an input capacitor. In supply-powered applications or battery applications with long leads to the battery, a low ESR 3.3µF capacitor reduces switching noise and peak currents. Design Example The example will use a Lumileds DS25 white LED. The key specifications are: Keep the inductor and output capacitor as close to the IC as possible. Make traces as short and wide as is feasible. Parasitic resistance and inductance reduce efficiency and increase ripple. Keep resistance in the battery connections as low as possible. In single cell applications, only 0.1Ω in the battery connections will have a dramatic effect in efficiency and battery life. I2R losses can exceed 100mW and the converter operates lower on the efficiency curve. VF (at IF= 350mA) = 3.4 ±0.6V RLED = 1Ω Peak Pulsed Forward Current = 0.5A 3490f 8 LTC3490 U W U U APPLICATIO S I FOR ATIO Red Luxeon LEDs is only 2.31V. The LTC3490 requires an additional 190mV for proper operation. In non-dimming applications, this can be accomplished with a 0.6Ω resistor in series with the LED. The resistor voltage drops too low in dimming applications, so a Schottky diode is recommended to keep sufficient voltage at the output at lower currents. The red, red-orange and amber Luxeon LEDs have a lower forward voltage than the white, blue and green LEDs. Since the LTC3490 internal circuitry is powered from the output, it requires a minimum LED voltage of 2.5V for reliable operation. The minimum forward voltage on the red LEDs U TYPICAL APPLICATIO S 2-Cell Adjustable Amplitude LED Driver 3.3µH VIN SW ON/OFF 2 NiMH OR ALKALINE CELLS CAP + LTC3490 + 4.7µF CTRL/SHDN LED LOBAT CELLS 1M LUMILEDS LUXEON LXHL-BW02 GND 3490 TA03 Soft Turn-Off LED Driver 3.3µH VIN SW CAP ON/OFF 1 NiMH OR ALKALINE CELL LTC3490 + CTRL/SHDN LED CELLS 1µF 1M LOBAT GND 350mA 4.7µF LUMILEDS LUXEON LXHL-BW02 3490 TA04 3490f 9 LTC3490 U TYPICAL APPLICATIO S Luxeon Red LED Driver Without Dimming 3.3µH ON/OFF SW VIN CAP 1 NiMH OR ALKALINE CELL LTC3490 + 4.7µF CTRL/SHDN LED 0.6Ω LOBAT CELLS 1M LUMILEDS LUXEON LXHL-BD03 GND 3490 TA06 Luxeon Red LED Driver with Dimming 3.3µH ON/OFF SW VIN CAP 1 NiMH OR ALKALINE CELL LTC3490 + 4.7µF CTRL/SHDN LED 1M MBRM120E LOBAT CELLS LUMILEDS LUXEON LXHL-BD03 GND 3490 TA07 Efficiency vs VIN with Red LED 90 RESISTOR 80 SCHOTTKY EFFICIENCY (%) 70 60 50 40 30 20 10 0 1 1.5 2 2.5 3 VIN (V) 3490 G06 3490f 10 LTC3490 U PACKAGE DESCRIPTIO DD Package 8-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1698) R = 0.115 TYP 5 0.38 ± 0.10 8 0.675 ±0.05 3.5 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) 3.00 ±0.10 (4 SIDES) PACKAGE OUTLINE 1.65 ± 0.10 (2 SIDES) PIN 1 TOP MARK (NOTE 6) (DD8) DFN 1203 0.25 ± 0.05 4 0.25 ± 0.05 0.75 ±0.05 0.200 REF 0.50 BSC 2.38 ±0.05 (2 SIDES) 1 0.50 BSC 2.38 ±0.10 (2 SIDES) 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1) 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 TOP AND BOTTOM OF PACKAGE S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 8 .245 MIN 7 6 5 .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) .030 ±.005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) 3 4 .053 – .069 (1.346 – 1.752) .004 – .010 (0.101 – 0.254) 0°– 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN 2 .014 – .019 (0.355 – 0.483) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) .050 (1.270) BSC SO8 0303 3490f 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. 11 LTC3490 U TYPICAL APPLICATIO LED Driver Drops to 20% Amplitude on Low-Battery Detect 3.3µH ON/OFF VIN SW CAP 1 NiMH OR ALKALINE CELL + LTC3490 1M 350mA/70mA CTRL/SHDN LED CELLS 1M 432k LOBAT GND 4.7µF LUMILEDS LUXEON LXHL-BWO2 3490 TA05 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT 1618 Constant Current, Constant Voltage 1.4MHz, High Efficiency Boost Regulator VIN: 1.6V to 18V, VOUT(MAX) = 34V, IQ = 1.8mA, ISD < 1µA, MS/EDD Packages LT1932 Constant Current, 1.2MHz, High Efficiency White LED Boost Regulator VIN: 1V to 10V, VOUT(MAX) = 34V, IQ = 1.2mA, ISD < 1µA, ThinSOT Packages LT1937 Constant Current, 1.2MHz, High Efficiency White LED Boost Regulator VIN: 2.5V to 10V, VOUT(MAX) = 34V, IQ = 1.9mA, ISD < 1µA, ThinSOTTM/SC70 Packages LTC3205 High Efficiency, Multi-Display LED Controller VIN: 2.8V to 4.5V, VOUT(MAX) = 6V, IQ = 50µA, ISD < 1µA, QFN24 Package LTC3216 1A Low Noise, High Current LED Charge Pump with Independent Flash/Torch Current Contol VIN: 2.9V to 4.4V, VOUT(MAX) = 5.5V, IQ = 300µA, ISD < 2.5µA, DFN Packge LTC3402 2A, 3MHz Micropower Synchronous Boost Converter VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = < 38µA, ISD < 1µA, MS/EDD Packages LTC3453 500mA Synchronous Buck-Boost High Current LED Driver in QFN VIN: 2.7V to 5.5V, VOUT(MAX) = 5.5V, IQ = 0.6mA, ISD < 6µA, QFN Package LT3465/LT3465A Constant Current, 1.2MHz/2.7MHz, High Efficiency White LED Boost Regulator with Integrated Schottky Diode VIN: 2.7V to 16V, VOUT(MAX) = 34V, IQ = 1.9mA, ISD < 1µA, ThinSOT Package LT3466 Dual Constant Current, 2MHz, High Efficiency White LED Boost Regulator with Integrated Schottky Diode VIN: 2.7V to 24V, VOUT(MAX) = 40V, IQ = 5mA, ISD < 16µA, DFN Package LT3479 3A, Full-Featured DC/DC Converter with Soft-Start and Inrush Current Protection VIN: 2.5V to 24V, VOUT(MAX) = 40V, IQ = 6.5mA, ISD < 1µA, DFN/TSSOP Packages ® ThinSOT is a trademark of Linear Technology Corporation. 3490f 12 Linear Technology Corporation LT/TP 0405 500 • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005