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.