Parallel RGB / HDMI Adapter High Speed PCB Design Kristoffer Scott

Applications HDMI to Parallel RGB Parallel RGB to HDMI TFT Display Driver Parallel RGB to HDMI Retrofit HDMI connector

Parallel RGB One pixel per clock Usually 16, 18, or 24 bit RGB color Frame synced with extra signals (VSYNC/HSYNC/DE)

HDMI TMDS Protocol 3 differential data channels 1 differential clock 100 Ω differential impedance Optional display data channel

FPGA Bridge Used to convert RGB into HDMI or vice-versa In-circuit programmable Level translation and differential signal drivers DSP/UI features

Design Priorities Cost Resolution/Framerate Power DSP/SW Features

Xilinx Spartan 3A Smaller version of the popular Spartan 3 Low cost (10.85 @1u on Digikey) “3A” part is ideal for bridging Optimized for I/O Differential signal drivers Similar banking and package to other more powerful Spartan boards

Design Features JTAG Programming interface Reversible with only BOM and SW change Can use RGB’s power supply or on-board supply DC plug is optional if RGB supplies enough power Flexible bit length

PCB Stack Initial estimate OSH Park 4 layer stackup: Thickness Layer Tolerance 1 mil solder resist +/-0.2mil 1.4 mil 1 oz copper   6.7 mil FR408 prepreg +/-.67mil 0.7 mil 0.5 oz copper 47 mil FR408 core +/-4.7mil

Next Steps Complete schematic and BOM Add terminations for HDMI-input configuration Determine which rails need DCDCs Add extra optional signals (e.g. audio, display control) Finalize PCB stack and HSD parameters Layout PCB Check manufacturing options and cost