AD9985A:  110 MSPS/140 MSPS Analog Interface for Flat Panel Displays

The AD9985A is a complete 8-bit, 140 MSPS, monolithic analog interface optimized for capturing RGB graphics signals from personal computers and workstations. Its 140 MSPS encode rate capability and full power analog bandwidth of 300 MHz support resolutions up to SXGA (1280 × 1024 at 75 Hz).

The AD9985A includes a 140 MHz triple ADC with internal 1.25 V reference, a PLL, and programmable gain, offset, and clamp control. The user provides only a 3.3 V power supply, analog input, and horizontal sync (Hsync) and Coast signals. Three-state CMOS outputs can be powered from 2.5 V to 3.3 V.

The AD9985A’s on-chip PLL generates a pixel clock from the Hsync input. Pixel clock output frequencies range from 12 MHz to 140 MHz. PLL clock jitter is 500 ps p-p typical at 140 MSPS. When the COAST signal is presented, the PLL maintains its output frequency in the absence of Hsync. A sampling phase adjustment is provided. Data, Hsync, and clock output phase relationships are maintained.

The AD9985 also offers full sync processing for composite sync and sync-on-green applications, variable analog input bandwidth control, variable SOGIN bandwidth control and selectable input filtering.

A clamp signal is generated internally or can be provided by the user through the CLAMP input pin. This interface is fully programmable via a 2-wire serial interface.

Fabricated in an advanced CMOS process, the AD9985A is provided in a space-saving 80-lead LQFP surface-mount Pb-free plastic package, and is specified over the –40°C to +85°C temperature range.

Applications

• RGB graphics processing
• LCD monitors and projectors
• Plasma display panels
• Scan converters
• Microdisplays
• Digital TVs