LM3646

The LM3646 utilizes a 4-MHz fixed-frequency synchronous boost converter to provide power to dual 1.5-A constant current LED sources. The high-side current sources allow for grounded cathode LED operation providing flash current up to 1.5 A total. An adaptive headroom regulation scheme ensures the LED currents remain in regulation and maximizes efficiency. The combination of dual LED driving capability, high LED current, small solution size and high level of adjustability make the LM3646 perfect for camera phone LED flash and torch applications.

The LM3646 is controlled through an I²C-compatible interface. The main features of the LM3646 include: a hardware flash enable (STROBE) input for direct triggering of the flash pulse, a hardware Torch enable (TORCH) for movie mode or flashlight functions, a TX input which forces the flash pulse into a low-current torch mode allowing for synchronization to RF power amplifier events or other high-current conditions, an integrated comparator designed to monitor an NTC thermistor and provide an interrupt to the LED current, and a programmable input voltage monitor which monitors the battery voltage and can reduce the flash current during low battery conditions. A hardware enable (ENABLE) input provides a hardware shutdown during system software failures.

The 4-MHz switching frequency, overvoltage protection, and adjustable current limit allow for the use of tiny, low-profile inductors and (10-µF) ceramic capacitors. The device is available in a small 20-bump DSBGA package and operates over the –40°C to 85°C temperature range.