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LED backlight controller enhances TV picture quality

18 Dec 2015

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Ams AG has unveiled a 16-channel LED TV backlight controller that enables local dimming of sections of a display screen to provide both improved picture quality and valuable power savings of up to 20-30 per cent. The AS3824 is geared for the latest HD and ultra high-definition (UHD, or 4K) TVs, as well as high dynamic range (HDR) monitors and displays.

The AS3824 includes a fully flexible 12bit PWM generator for each of its 16 channels, to enable sections of a display screen to be dimmed independently. Each PWM generator may be synchronised with an external synchronisation signal.

The 16-channel independent dimming capability means that the backlight intensity of each section can be precisely controlled to match the picture content of each successive frame on display. When a section of the frame needs to be dark, the LEDs illuminating just that section may be dimmed independently of the rest, enabling a TV to reproduce faithfully even the blackest of blacks, and enhancing the perceived picture quality. By contrast, conventional global backlight controllers cannot prevent some light from leaking into sections of the display screen that should be black, thus reproducing black as grey.

AS3824

The local dimming enabled by the AS3824 also provides for additional system power savings compared to global backlight controllers.

The AS3824 backlight controller features a precise internal 10bit DAC, which provides accurate (±0.5 per cent) global control of the current through external MOSFETs or bipolar transistors. It supports all LED backlight topologies, with no limit on the current through or voltage across the LEDs.

The device also includes a supplementary 8bit current-control DAC for each of the 16 channels, which can be used to boost or lower the current locally through the LEDs in certain frames, thereby increasing dynamic contrast ratios. This enables the AS3824 to support HDR monitors and HDR TVs. The AS3824 is backed by a comprehensive set of protection functions, including thermal shutdown when the temperature exceeds 140°C, and open and short LED detection. The device may be programmed via a serial peripheral interface and daisy-chained to as many AS3824 devices as are needed in the application.

AS3824 block diagram

AS3824 block diagram

The AS3824 is available for sampling. Unit pricing is $1.25 in order quantities of 1,000. A demonstration kit for the AS3824 is available on request.

Evaluation kit for AS3824

Evaluation kit for AS3824




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