Overview: Bt481A
110 MHz 256-Word Color Palette 15-, 16-, and 24-Bit True Color Power-Down RAMDAC
Designed specifically for high-performance color graphics, the Bt481A RAMDAC supports three true-color modes: 15-bit (5:5:5, 32 K colors) TARGA format, 16-bit (5:6:5, 65 K colors) XGA format, and 24-bit BGR (8:8:8, RGB/ BGR, 16.8 M colors) true-color format. It also supports 8-bit pseudo-color format (256 colors). The Bt481A has a 256 x 18 (24) lookup table RAM, 15 x 8 (24) overlay registers, and triple 8-bit D/A converters. Both 6- and 8-bit color modes are supported. A power-down mode is available on the Bt481A to reduce power requirements when the analog outputs are not used. This is useful in laptop puter systems that require the option to drive an external RGB monitor. The Bt481A has on-chip analog output parators to simplify diagnostics and debugging, with the result output onto the SENSE* pin. Also included is an on-chip voltage reference to simplify use of the device. The Bt481A generates RS-343-patible video signals into a doubly terminated load.
