16-channel LED backlight controller improves TV picture quality
The AS3824 backlight controller is intended 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.
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 synchro-nized with an external synchronization 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.
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 10-bit DAC, which provides accurate (±0.5%) global control of the current through external MOSFETs or bipolar transistors. The device supports all LED backlight topologies, with no limit on the current through or voltage across the LEDs.
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 pro-grammed via a serial peripheral interface and daisy-chained to as many AS3824 devices as are needed in the application.
Availability and Pricing
The AS3824 is available for sampling now. Unit pricing is $1.25 in order quantities of 1,000. A demonstration kit for the AS3824 is available on request.
www.ams.com/LED-backlight-controller/AS3824.
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