New 16-Channel LED Backlight Controller Improves TV Picture Quality

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A new 16-channel LED TV backlight controller for use in the latest high-definition (HD) and ultra high-definition (UHD, or ‘4K’) televisions, as well as high dynamic range (HDR) monitors and displays, is introduced by ams AG. The AS3824 is said to provide both improved picture quality and valuable power savings of up to 20-30 per cent by performing local dimming of sections of a display screen.

The AS3824 includes a fully flexible 12-bit 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 local dimming enabled by the AS3824 also provides for additional system power savings compared to global backlight controllers.

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.

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The AS3824 backlight controller features a precise internal 10-bit 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.

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The device also includes a supplementary 8-bit 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.

“With the introduction of the AS3824, ams is the first semiconductor manufacturer to provide an LED backlighting controller that is ready to support the latest Dolby Vision standard for UHD displays, enabling display manufacturers to achieve a stunning contrast between light and dark and the deepest black rendition”, said Bernd Krafthoefer, Marketing Manager for Power Management business line at ams.

The AS3824 is available for sampling now. Unit pricing is US$1.25 in order quantities of 1000. A demonstration kit for the AS3824 is available on request.

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