LM3555 Datasheet, PDF (1/2 Pages) National Semiconductor (TI) – Synchronous Boost Converter with 500 mA High Side LED Driver and Dual-Mode Control Interfacev

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
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 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
■ ^{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}
60mA to 500mA
■ ^{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 Over-Voltage Protection}
■ ^{Output and LED Short-Circuit Protection}
■ ^{400kHz I2C Compatible Interface}
■ ^{12–Bump, 1.575 mm x 2.1 mm x 0.6 mm micro SMD}
Package (TLA12BCA)
Applications
■ ^{Camera Phone LED Flash}
Typical Application Circuits
© 2009 National Semiconductor Corporation 300794
30079401
www.national.com