LM3554 Datasheet, PDF (1/4 Pages) National Semiconductor (TI) – Synchronous Boost Con

LM3554 PRODUCT BRIEF
June 8, 2009
Synchronous Boost Converter with 1.2A Dual High Side
LED Drivers and I²C Compatible Interface
General Description
The LM3554 is a 2 MHz fixed frequency, current mode syn-
chronous boost converter. The device is designed to operate
as a dual 600mA (1.2A total) constant current driver for high
current white LEDs, or as a regulated 4.5V or 5V voltage
source.
The dual high side current sources allow for grounded cath-
ode LED operation. An adaptive regulation method ensures
the current source for each LED remains in regulation and
maximizes efficiency.
The main features include: an I²C compatible interface for
controlling the LED current or the desired output voltage, a
hardware Flash enable input for direct triggering of the Flash
pulse, and dual TX inputs which force the Flash pulse into a
low current Torch mode allowing for synchronization to RF
power amplifier events or other high current conditions. Ad-
ditionally, an active high hardware enable (HWEN) input pro-
vides a hardware shutdown during system software failures.
Five protection features are available within the LM3554 in-
cluding a software selectable input voltage monitor, an inter-
nal comparator, for interfacing with an external temperature
sensor, four selectable current limits to ensure the battery
current is kept below a predetermined peak level, an over-
voltage protection feature to keeps the output voltage below
the OVP threshold in case of an open LED, and an output
short circuit protection which limits the output current during
an output short to GND. Additionally, the device provides var-
ious fault indicators including: a thermal fault flag indicating
the LED temperature has tripped the thermal threshold, a flag
indicating a TX event has occured, a flag indicating the flash
timeout counter has expired, a flag indicating the devices die
temperature has reached the thermal shutdown threshold,
and a flag indicating an open or short LED.
Notice: This document is not a full datasheet. For more
imformation regarding this product, or to order samples,
please contact your National Semiconductor sales office
or visit http://www.national.com/support/dir.html.
Features
■ ^{Dual High Side Current Sources}
■ ^{Grounded Cathode Allowing for Better Heatsinking and}
LED Routing
■ ^{>90% Efficiency}
■ ^{Ultra-Small Solution Size: < 23mm2}
■ ^{Four Operating Modes: Torch, Flash, LED Indicator and}
Voltage Output
■ ^{Accurate and Programmable LED Current from 37.5mA to}
1.2A
■ ^{Programmable 4.5V or 5.0V Constant Output Voltage}
■ ^{Hardware Flash and Torch Enable}
■ ^{LED Thermal Sensing and Current Scaleback}
■ ^{Software Selectable Input Voltage Monitor}
■ ^{Programmable Flash Timeout}
■ ^{Dual Synchronization Inputs for RF Power Amplifier Pulse}
Events
■ ^{Open and Short LED Detection}
■ ^{Active High Hardware Enable for Protection Against}
System Faults
■ ^{400kHz I2C Compatible Interface}
■ ^{16-Bump (1.7mm × 1.7mm × 0.6mm) µSMD}
Applications
■ ^{Camera Phone LED Flash Controller}
■ ^{Class D Audio Amplifier Power}
■ ^{LED Current Source Biasing}
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