IN

OUT

TEMP

SW

ENABLE

TORCH

TX

SDA

SCL

GND

1 2H

10 2F

10 2F

STROBE

LED2

2.7V to 5.5V

LED1

LM3646

1200

1400

1600

1800

2000

2200

2400

2600

2800

2.8

3

3.2

3.4

3.6

3.8

4

4.2

4.4

4.6

4.8

5

V

TA = +25ºC

TA = -40ºC

TA = +85ºC

C032

I

LM3646

www.ti.com

SNVS962 – DECEMBER 2013

Compatible Interface

Check for Samples: LM3646

1

FEATURES

DESCRIPTION

The LM3646 is a 4 MHz fixed-frequency, Current

2

•

High-Side Current Sources allowing for

Mode synchronous boost converter. The device is

Grounded LED Cathode for Improved Thermal

designed to operate as a dual 1.5A constant current

Management

driver for high current LEDs. The high-side current

•

> 85% Efficiency in Torch and Flash Modes

sources allow for grounded cathode LED operation

providing Flash current up to 1.5A total. An adaptive

•

headroom

regulation

scheme

ensures

the

LED

•

Accurate and Programmable Flash LED

currents

remain

in

regulation

and

maximizes

Current from 24 mA to 1.5A in 11.7 mA steps

efficiency.

•

Accurate and Programmable Torch LED

The LM3646 is controlled via an I²C-compatible

Current from 2.5 mA to 187 mA in 1.5 mA

interface. The main features of the LM3646 include: a

steps

hardware flash enable (STROBE) input for direct

•

Dual 1.5A High-Side Current Sources for Dual

triggering of the Flash pulse, a hardware Torch

LED Drive

enable (TORCH) for Movie Mode or Flashlight

functions, a TX input which forces the flash pulse into

•

Hardware Flash and Torch Enables

a

low-current

Torch

Mode

allowing

for

•

Hardware Enable Pin

synchronization to RF power amplifier events or other

•

Soft-Start Operation for Battery Protection

high-current conditions, an integrated comparator

designed to monitor an NTC thermistor and provide

•

LED Thermal Sensing and Current Scale-Back

an interrupt to the LED current, and a programmable

•

Synchronization Input for RF Power Amplifier

input voltage monitor which monitors the battery

Pulse Events

voltage and can reduce the flash current during low

•

VIN Flash Monitor Optimization

battery conditions. A hardware enable (ENABLE)

input provides a hardware shutdown during system

•

1 MHz I²C-Compatible Interface

software failures.

•

I²C-Programmable NTC Trip Point

The

4

MHz

switching

frequency,

over-voltage

•

0.4 mm pitch, 20-Bump DSBGA

protection, and adjustable current limit allow for the

use of tiny, low-profile inductors and (10

μF) ceramic

APPLICATIONS

capacitors. The device is available in a small 20-

•

Camera Phone LED Flash/Torch

bump DSBGA package and operates over the

−40°C

to +85°C temperature range.

SYSTEM PERFORMANCE

TYPICAL APPLICATION CIRCUIT

1

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Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2

All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Copyright © 2013, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.