1 Features

1• Input Voltage Range: 2.8 V to 5.5 V

• Drives up to Four LEDs With up to 30 mA each

• Regulated Current Sources with 0.2% (Typical)

Matching

• 3/2×, 1× Gain Transition Based on LED Vƒ

• Peak Efficiency Over 85%

• PWM Brightness Control

• Very Small Solution Size - No Inductor

• Fixed 750-kHz Switching Frequency

• < 1-μA Shutdown Current

2 Applications

• White LED Display Backlights

• White LED Keypad Backlights

• General Purpose LED Lighting

3 Description

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.