1FEATURES
2• Single Chip White LED Flash and Backlight
Driver
• 1.5A Flash LED Current
• Dual String Backlight Control (40V Max VOUT)
• 128 Level Exponential and Linear Brightness
Control
• PWM Input for CABC
• Programmable Over-Voltage Protection
(Backlight)
• Programmable Current Limit (Flash)
• Programmable Switching Frequency
• Optimized Flash Current During Low-Battery
Conditions

APPLICATIONS
• White LED Backlit Display Power
• White LED Camera Flash Power

DESCRIPTION
The LM3639A is a single-chip white LED Camera
Flash Driver + LCD Display Backlight Driver. The lowvoltage,
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
efficiency.
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.