1 Features

1? High-Voltage High-Side Current Source Allows for

Grounded Cathode LED Operation

? Synchronous Boost Converter

? Peak Converter Efficiency > 90%

? Accurate and Programmable LED Current

Ranging From 60 mA to 500 mA

? Adaptive LED Current Range Based on LED

Configuration

? Dedicated Indicator Current Source

? Dedicated Torch and Strobe Pins

? Dual Mode Control (General Purpose or I2C)

? Broken Inductor Detection

? Output Overvoltage Protection

? Output and LED Short-Circuit Protection

? 400-kHz I2C-Compatible Interface

2 Applications

Camera Phone LED Flash

3 Description

The LM3555 is a 2-MHz fixed-frequency, currentmode

synchronous boost converter designed to drive

either a single flash LED at 500 mA or two series

flash LEDs at 400 mA. A high-voltage current source

allows the LEDs to be terminated to the GND plane

eliminating the need for an additional return trace

back to the device.

A dual-mode control interface allows the user to

configure the LM3555 with a general-purpose

interface using two enable pins for control or an I2C

allowing a higher level of control. Both interfaces

allow access to the indicator, assist light, and flash

modes. A dedicated STROBE pin provides a direct

interface to trigger the flash event, while an external

TORCH pin provides an additional method for

enabling the LEDs in a constant current mode.

The LM3555 can adaptively scale the maximum flash

level delivered to the LEDs based upon the flash

configuration, whether it be a single LED or two LEDs

in series.

Eight protection features are available on the LM3555

ranging from overvoltage protection to broken

inductor detection. The LM3555 has four selectable

inductor current limits to help the user select an

inductor that is appropriate for the design.