1 Features

1• 1.5 A Total Allowed LED Current During Operation

(I LED1 + ILED2 = 1.5 A)

• Dual Independent LED Current Source

Programmability

• Accurate and Programmable LED Current Range

from 1.4 mA to 1.5 A

• Optimized Flash LED Current During Low Battery

Conditions (IVFM)

• > 85% Efficiency in Torch Mode (@ 100 mA) and

Flash Mode (@1 A to 1.5 A)

• Grounded Cathode LED Operation for Improved

Thermal Management

• Small Solution Size: < 16 mm2

• Hardware Strobe Enable (STROBE)

• Synchronization Input for RF Power Amplifier

Pulse Events (TX)

• Hardware Torch Enable (TORCH/TEMP)

• Remote NTC Monitoring (TORCH/TEMP)

• 400-kHz I2C-Compatible Interface

– LM3643 (I2C Address = 0x63)

– LM3643A (I2C Address = 0x67)

2 Applications

Camera Phone White LED Flash

3 Description

The LM3643 is a dual LED flash driver that provides

a high level of adjustability within a small solution

size. The LM3643 utilizes a 2-MHz or 4-MHz fixed-

frequency synchronous boost converter to provide

power to the dual 1.5-A constant current LED

sources. The total LED current the LM3643 boost can

deliver is 1.5 A (ILED1 + ILED2 ). The dual 128 level

current sources provide the flexibility to adjust the

current ratios between LED1 and LED2 with each driver capable of delivering a maximum of 1.5 A (ex:

ILED1 = 1.5 A and ILED2 = 0FF, ILED1 = 0FF and ILED2 =

1.5 A, or a current configuration with a current less

than 1.5 A , ILED1 = 950 mA and ILED2 = 250 mA). An

adaptive regulation method ensures the current

sources remain in regulation and maximizes

efficiency.

Features of the LM3643 are controlled via an I2C-

compatible interface. These features include:

hardware flash and hardware torch pins (STROBE

and TORCH/TEMP), a TX interrupt, and an NTC

thermistor monitor. The device offers independently

programmable currents in each output leg to drive the LEDs in a Flash or Movie Mode (Torch) condition.

The 2-MHz or 4-MHz switching frequency options,

overvoltage protection (OVP), and adjustable current

limit allow for the use of tiny, low-profile inductors and

(10-μF) ceramic capacitors. The device operates over

a –40°C to 85°C ambient temperature range.