LED Driver: 6 Channels with Phase Shift Control

Posted on May 19, 2010 by Rust

We can use ISL97676 as a LED driver that drives 6 channels of LED current for TFT-Display. The ISL97676 is used to drive 6 channels of LED to support 78 LEDs from 4.5V to 26V or 48 LEDs from a boost supply of 2.7V to 26V and a separate 5V bias supply on the ISL97676 Vin pin.

LED Driver 6 Channels with Phase Shift Control circuit schematic diagram

For non-uniformity of the forward voltage drops in the LED strings with its 6 voltage controlled-current source channels is compensated by the ISL97676. The highest LED forward voltage string for output regulation is monitored by the headroom control to minimize the voltage headroom and power loss in the typical multi string operation.

Two PWM Dimming modes are offered by Intersil: The ISL97676 digitizes the incoming PWM signal and provides 8-bit dimming. The resistor set the PWM frequency. This will produce dimming frequency between 100Hz to 30KHz. Secondly, direct PWM mode without phase shift, where the dimming follows the input PWM signal.

To help eliminate or reduce the video and audio noise interference from the backlight driver operation, we can use the ISL97676 features channel phase shift control to minimize the input, output ripple characteristics and load transients as well as spreading the light out.

Refers to the datasheet for more information about how to select the values of each components. [Source: Intersil]

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