LM3554

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SNVS549A – JUNE 2009 – REVISED APRIL 2011

Compatible Interface

Check for Samples: LM3554

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FEATURES

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Dual Synchronization Inputs for RF Power

Amplifier Pulse Events

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Dual High Side Current Sources

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Open and Short LED Detection

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Grounded Cathode Allowing for Better Heat

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Active High Hardware Enable for Protection

Sinking and LED Routing

Against System Faults

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>90% Efficiency

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16-Bump (1.7mm × 1.7mm × 0.6mm) micro

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Four Operating Modes: Torch, Flash, LED

SMD

Indicator and Voltage Output

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Accurate and Programmable LED Current from

APPLICATIONS

37.5mA to 1.2A

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Camera Phone LED Flash Controller

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Programmable 4.5V or 5.0V Constant Output

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Class D Audio Amplifier Power

Voltage

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LED Current Source Biasing

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Hardware Flash and Torch Enable

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LED Thermal Sensing and Current Scaleback

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Software Selectable Input Voltage Monitor

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Programmable Flash Timeout

DESCRIPTION

The LM3554 is a 2MHz fixed frequency, current mode synchronous 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 cathode LED operation. An adaptive regulation method

ensures the current source for each LED remains in regulation and maximizes efficiency.

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. Additionally, an active high hardware enable (HWEN) input provides a hardware

shutdown during system software failures.

Five protection features are available within the LM3554 including a software selectable input voltage monitor, an

internal 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 limit the output

voltage during LED open circuits, and an output short circuit protection which limits the output current during

shorts to GND. Additionally, the device provides various fault indicators including: a thermal fault flag indicating

the LED temperature has tripped the thermal threshold, a flag indicating a TX event has occurred, 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.

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Products conform to specifications per the terms of the Texas

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