LED DRIVER SW CAP POWERWISE LLP-14
The LM27951 is a switched capacitor white-LED driver capable of driving up to four LEDs with 30 mA through each LED. Its four 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 2.8 V to 5.5 V 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 750-kHz switching frequency optimized for portable applications. The LM27951 consumes less than 1 µA of supply current when shut down. The LM27951 is available in a 14-pin no-pullback WSON package.