Integrated, 2-channel, high-brightness automotive LED driver

December 15, 2014 // By Graham Prophet
For use in automotive display backlights, automotive lighting applications and LCD backlights, Maxim has posted detail of the MAX16838B which it says is the only-available 2-String HB LED driver providing 10000:1 dimming ratio: the part has high-voltage boost and and a SEPIC controller

The device is a dual-channel LED driver that integrates both the DC-DC switching boost regulator and two 150-mA current sinks. A current-mode switching DC-DC controller provides the necessary voltage to both strings of HB LEDs. The MAX16838B accepts a 4.75V to 40V input voltage range and directly withstands automotive load-dump events. For a 5V ±10% input voltage, VIN is connected directly to VCC. The wide input range allows powering of high-brightness LEDs for small-to-medium-sized LCD displays in automotive and display backlight applications.

An internal current-mode switching DC-DC controller supports the boost or SEPIC topologies and operates in an adjustable frequency range between 200 kHz and 2 MHz. The current-mode control provides fast response and simplifies loop compensation. The MAX16838B also features an adaptive output-voltage adjustment scheme that minimises the power dissipation in the LED current sink paths.

The channel current is adjustable from 20 mA to 150 mA using an external resistor. The external resistor sets both channel currents to the same value. The device allows connection of both strings in parallel to achieve a maximum current of 300 mA in a single channel. The device also features pulsed dimming control with minimum pulse widths as low as 0.5 µsec, on both channels through a logic input (DIM).

MAX16838B includes an output overvoltage protection, open LED, shorted LED detection, and overtemperature protection. The device operates over the -40°C to +125°C automotive temperature range and is available in 20-pin TSSOP and 4 x 4 mm, 20-pin TQFN packages.

Maxim Integrated;