The LM3639A is a single-chip white LED Camera Flash Driver + LCD Display Backlight
Driver. The low-voltage, high-current flash LED driver is a synchronous boost which provides the
power for a single flash LED at up to 1.5A or dual LEDs at up to 750 mA each. The high-voltage
backlight driver is a dual-output asynchronous boost which powers dual LED strings at up to 40V and
30 mA per string. An adaptive regulation method in both boost converters regulates the headroom
voltage across the respective source/sink to ensure the LED current remains in regulation while
maximizing efficiency. The LM3639A's flash driver is a 2MHz or 4MHz fixed-frequency synchronous
boost converter plus 1.5A constant current driver for a high-current white LED. The high-side
current source allows for grounded cathode LED operation providing Flash current up to 1.5A. An
adaptive regulation method ensures the current source remains in regulation and maximizes
The device is controlled by an I2C-compatible interface.
Features for the flash LED driver include a hardware flash enable (STROBE) allowing a logic input
to trigger the flash pulse, and a TX input for synchronization to RF power amplifier events or
other high current conditions. Features for the LCD backlight driver include a PWM input for
content adjustable backlight control, 128 exponential or linear brightness levels, programmable
over-voltage protection, and selectable switching frequency (500 kHz or 1 MHz).
The device is available in a tiny 1.790 mm x 2.165 mm x 0.6 mm 20-bump, 0.4 mm pitch
DSBGA package and operates over the −40°C to +85°C temperature range.
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