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.