The new backlight controller is designed for use in recent HD TVs or UHD (4K) TVs, as well as HDR (high dynamic range) monitors and displays.

The AS3824 includes a fully flexible 12-bit PWM generator suitable for each of the 16 channels, allowing independent dimming of sections of the display screen. Each PWM generator can be synchronized with an external synchronization signal.

The independent dimming capability of the 16 channels means that the backlight intensity of each section can be precisely controlled to match the screen content of each consecutive frame on the display. As part of the frame darkens, the LEDs illuminating that part can be dimmed independently from the rest, allowing the TV to faithfully reproduce color even in the darkest blacks, improving perceived picture quality.

Conversely, the conventional global backlight controller cannot prevent light leakage in parts of the display screen that should be processed as black, resulting in black being reproduced as gray.

Local dimming implemented with the AS3824 also provides additional power savings to the system compared to a global backlight controller.

The AS3824 backlight controller integrates a precise 10-bit DAC that provides precise (±0.5%) global control of the current via an external MOSFET or bipolar transistor. It supports all LED backlight topologies without limitations on the current and voltage to the LEDs.



AS3824 block diagram

The device also includes an additional 8-bit current control DAC for each of the 16 channels. This can be used to partially increase or decrease the current through the LEDs during a given frame, thereby increasing the dynamic contrast ratio. This enables the AS3824 to support HDR monitors and HDR TVs.

The AS3824 is supported by a comprehensive set of protection features, including thermal shutdown when temperatures exceed 140°C, and open and short LED detection. The device can be programmed via the serial peripheral interface and daisy-chained to accommodate a large number of AS3824 devices as required by the application.

“With the introduction of the AS3824, ams is the first semiconductor manufacturer to offer an LED backlight controller that supports the latest Dolby Vision™ standard for UHD displays. This enables display manufacturers to achieve excellent contrast between light and dark areas and very deep black renditions,” said Bernd Krafthoefer, marketing manager for the Power Management business line at ams.

The AS3824 is available for sampling now. Unit pricing is $1.25 in quantities of 1,000. A demonstration kit for the AS3824 is available upon request. For sample requests and detailed technical information, see www.ams.com/LED-backlight-controller/AS3824.