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.