TMDS1204: Regarding the use of AC coupling and DC coupling for HDMI signal transmission

Hi,

When using Ac coupling, the common mode of the HDMI signal will be 0V. This means that the data will be centered around 0V. This will require the use of external AC coupling capacitor and configuring the TMDS1204 correctly. Using AC coupling will result in the best signal quality.

When using DC coupled HDMI, the common mode of the HDMI signaling will be 3.3V. This mean the data will be centered around 3.3V. There are no external components required for this as the termination to 3.3V is handles internally. This will result in slightly worse signal quality. The impedance across the traces will be the same at 100 ohm differential.