LM27951 Datasheet | National Semiconductor

November 2005 .. LM27951 White LED Adaptive 1.5X/1X Switched Capacitor Current Driver LM27951 White LED Adaptive 1.5X/1X Switched Capacitor Current Driver General Description The LM27951 is a switched capacitor white-LED driver capable of driving up to 4 LEDs with 30m A through each LED. Its 4 tightly regulated current sources ensure excellent LED current and brightness matching. LED drive current is programmed by an external sense resistor. The LM27951 operates over an input voltage range from 3.0V to 5.5V and requires only four low-cost ceramic capacitors. The LM27951 provides excellent efficiency without the use of an inductor by operating the charge pump in a gain of 3/2, or in a gain of 1. Maximum efficiency is achieved over the input voltage range by actively selecting the proper gain based on the LED forward voltage requirements. The LM27951 uses constant frequency pre-regulation to minimize conducted noise on the input. It has a fixed 750k Hz switching frequency optimized for portable applications. The LM27951 consumes less than 1µA of supply current when shut down. The LM27951 is available in a 14-pin No-Pullback Leadless Leadframe Package: LLP-14. Features n n n n n n n n n n Drives up to 4 LEDs with up to 30m A each Regulated current sources with 0.2%(typ.) matching 3/2x, 1x Gain transition based on LED VF Peak Efficiency Over 85% Input Voltage Range: 3.0V to 5.5V PWM Brightness Control Very Small Solution Size - NO INDUCTOR Fixed 750k Hz Switching Frequency < 1µA Shutdown Current 14-pin LLP Package: 4.0mm X 3.0mm X 0.8mm Applications n White LED Display Backlights n White LED Keypad Backlights n General Purpose LED Lighting Typical Application Circuit © 2005 National Semiconductor Corporation DS201717 .national. Connection Diagram LM27951 14-pin No-Pullback Leadless Leadframe Package (LLP-14) 4mm x 3mm x 0.8mm NS Package Number SDA14A .. Pin Descriptions Pin 1 2 3 4 5 6 7 8 9...