LM3561 Datasheet, PDF (2/36 Pages) Texas Instruments – LM3561 Synchronous Boost Converter with 600mA High Side LED Driver and I 2 C-Compatible Interface

LM3561
June 21, 2011
Synchronous Boost Converter with 600mA High Side LED
Driver and I²C-Compatible Interface
General Description
The LM3561 is a 2 MHz fixed-frequency, current mode syn-
chronous boost converter. The device is designed to operate
as a single 600mA constant current driver for high-current
white LEDs. The high side current source allows for grounded
cathode LED operation while the 250mV regulated headroom
voltage ensures that the LED current is well regulated and
efficiency remains high.
The main features of the LM3561 include: an I²C-compatible
interface for controlling the LED current, a hardware Flash
enable input for direct triggering of the Flash pulse, dual TX
inputs (TX1 and TX2) which force the Flash pulse into a low-
current Torch mode during high battery current instances, an
active high hardware enable (HWEN) allowing for fast hard-
ware shutdown during system software failures, a dual mode
pin which serves as either an indicator LED driver at up to
18mA or as a dedicated comparator input with an internal 1V
reference, designed to monitor the voltage across a negative
temperature coefficient thermistor (NTC), and a pro-
grammable input voltage monitor which monitors IN and can
reduce the flash current or shutdown the device during low
battery conditions.
Seven fault flags are available for read back over the I²C-
compatible bus. These include: a flash timeout flag indicating
the flash pulse has reached the end of the programmable
timeout duration, a thermal shutdown flag indicating the
LM3561's die temperature has exceeded 150°C, an LED fault
flag indicating the output voltage has tripped the over-voltage
threshold, or the LED has become shorted, TX1 and TX2 in-
terrupt flags indicating if either of the TX inputs have been
triggered, an NTC flag indicating the LED has experienced an
over temperature condition, and a VIN Monitor flag indicating
the input voltage has fallen below the VIN Monitor threshold.
The LM3561 is available in a tiny (1.215mm × 1.615mm ×
0.6mm) 12-bump micro SMD and operates over the -40°C to
+85°C temperature range.
Features
■ ^{High Side Current Source allowing for Grounded LED}
Cathode
■ ^{Up to 90% Efficient}
■ ^{Ultra-Small Solution Size: < 16mm2}
■ ^{Three Operating Modes: Torch, Flash, and LED Indicator}
■ ^{Accurate and Programmable LED Current from 18mA to}
600mA
■ ^{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}
■ ^{12-Bump (1.215mm × 1.615mm × 0.6mm) micro SMD}
Applications
■ ^{Camera Phone LED Flash Controller}
■ ^{LED Current Source Biasing}
Typical Application Circuits
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Example Layout
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