January 15, 2009

LM3555 PRODUCT BRIEF

Synchronous Boost Converter with 500 mA High Side LED

Driver and Dual-Mode Control Interface

General Description

The LM3555 is a 2 MHz fixed frequency, current mode syn-

chronous 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 IC.

A dual mode control interface allows the user to configure the

LM3555 with a general purpose interface using two enable

Both interfaces allow access to the indicator, assist light and

flash modes. A dedicated Strobe pin provides a direct inter-

face 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 LED/LEDs based upon the flash configura-

tion, whether it be a single LED or two LEDs in series.

Eight protection features are available on the LM3555 ranging

from over-voltage 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.

Features

Grounded Cathode LED Operation

60mA to 500mA

Package (TLA12BCA)

Applications

Typical Application Circuits

30079401

© 2009 National Semiconductor Corporation

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