1. Parallel RGB / HDMI Adapter
High Speed PCB Design
Kristoffer Scott

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

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

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

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

6. Design Priorities
Cost
Resolution/Framerate
Power
DSP/SW Features

7. Xilinx Spartan 3A Smaller version of the popular Spartan 3
Low cost 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

9. 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

10. 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

11. 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