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.