Flash LED drivers deliver high-current stability in portable devices

25-09-2019 | Diodes Inc | Lighting Technologies

Diodes Incorporated now offers the AL3644, a high-speed, dual-channel flash LED driver created to support advanced camera flash and torch functionality, as provided by the most recent smartphones and other portable consumer devices. Key features comprise independently controlled output currents configured through an I2C-compatible interface and the capability to consolidate two devices (with different device identification addresses) to drive four LEDs up to 6A for quad-channel applications. The device is provided in chip-scale packaging and combines flexible switching-frequency abilities with constant output current.

The device uses a constant-frequency, synchronous-boost, current-mode PWM converter to provide up to 1.5A for each of the two constant current sources over its 2.5V to 5V input voltage range. The I2C-compatible interface, running at up to 400kHz, is employed to configure the device to provide a constant current at one of 128 levels between 1.4mA and 1.5A. The ratio between the two outputs is adjustable in the I2C-compatible interface.

Two switching-frequency options, 2MHz and 4MHz, are offered, providing engineers better flexibility while simplifying the overall design. The higher switching frequency also enables smaller passive components to be employed, such as low-profile inductors and small 10μF ceramic capacitors, lessening the overall BOM.

As well as being the first LED driver from the company to offer an I2C-compatible interface, the device also integrates a comparator that can be utilised with an external NTC to identify thermal variations. An input voltage monitor makes sure the output current remains stable if, for example, the input voltage level decreases as the device’s battery supply falls. Fault status bits, interrogated over the I2C-compatible interface, offer a host controller with operational data, such as current flash time-out, LED open/short failure, thermal shutdown, LED overtemperature, and input undervoltage.

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