AL3157 HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT Description Pin Assignments The AL3157 is a low noise, constant frequency charge pump DC/DC converter that uses a Dual mode load switch ( Top View ) (1x), and doubling (2x) conversion for driving white LEDs. Low external part count (one 1F flying capacitor and two 1 12 EN2 D1 2.2F capacitors at VIN and VOUT) make this part ideally suited for small, battery-powered applications 2 11 PGND EN1 The AL3157 drives 3 channels at up to 30mA for small 3 10 C D2 N screen backlighting and an additional channel up to 210mA Exposed Pad for LED Flash or LED Flashlight All from a 2.7V to 5.5V 4 9 V GND IN input. 5 8 D3 C P The AL3157 uses two control inputs (EN1/2) to 6 7 D4 enable/disable it and PWM dim the LED current. EN2 V OUT controls/PWM dims the backlight LEDs at 30mA per channel and EN1 controls/PWM dims the Flash/Flashlight U-DFN3030-12 LEDs at 210mA. Each output is equipped with built-in protection for V OUT short circuit and auto-disable for LED failure conditions. Built-in soft-start circuitry prevents excessive in-rush current during start-up and mode switching. A low-current shutdown feature disconnects the load from V to reduce IN quiescent current less than 1A. The AL3157 is available in a lead-free, space-saving thermally enhanced 12-pin 3x3mm DFN package. Features Applications Dual-Mode 1x and 2x Charge Pump Smart Touch Phone LED Backlighting Up to 300mA drive capability PDA White LED backlighting o 3-channel for backlight 30mA/ch Backlighting + Torch light o 1-channel for Flight/light 210mA V Range: 2.7V to 5.5V IN Two simple PWM dimming control inputs up to 50kHz 1.2 MHz Constant Switching Frequency Built-In Thermal, Open-Circuit and V short circuit OUT Protection Soft Start for reducing in-rush current I <1A in Shutdown Q Thermally-Enhanced DFN3030-12 Package: Available in Green Molding Compound (No Br, Sb) Lead Free Finish/ RoHS Compliant (Note 1) Notes: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at AL3157 HIGH EFFICIENCY 1x/2x CHARGE PUMP LED DRIVER FOR SMALL SCREEN BACKLIGHTING AND FLASHLIGHT Pin Descriptions Pin Name Pin Number Description EN2 1 Enable Pin 2: Controls outputs D2, D3 and D4 PGND 2 Charge Pump Switch Ground: Connect to GND C 3 Negative Terminal of Flying Capacitor N V 4 Input Power Supply. Decouple with a 2.2F capacitor between this pin and ground. IN C 5 Positive Terminal of Flying Capacitor P Charge pump output to drive D1~D4 load circuit. Decouple with a 2.2F capacitor between V 6 OUT this pin and ground. D4 7 Current sink input 4. Drive up to 30mA LED current. Connect to V when un-used. OUT D3 8 Current sink input 3. Drive up to 30mA LED current. Connect to V when un-used. OUT GND 9 Ground D2 10 Current sink input 2. Drive up to 30mA LED current. Connect to V when un-used. OUT EN1 11 Enable Pin 1: Controls output D1 D1 12 Current sink input 1. Drive up to 210mA LED current. Connect to V when un-used. OUT EP EP PAD Exposed Pad (bottom). Connect to GND directly underneath the package. Functional Block Diagram C C N P V OUT V SHORT OVER IN CHARGE PUMP CIRCUIT VOLTAGE SWITCHES PROTECTION PROTECTION EN1 DIGITAL CONTROL BLOCK EN2 D1 BANDGAP D2 OSCILLATOR D3 OVER CURRENT D4 TEMPERATURE CONTROL PROTECTION UNDER VOLTAGE LOCKOUT GND 2 of 9 March 2011 AL3157 Diodes Incorporated www.diodes.com Document number: DS35116 Rev. 1 - 2 NEW PRODUCT