TMDS181: Hardware schematic design recommendation

Errol Leon6

Part Number: TMDS181

Hello team,

My customer is designing TMDS181 into their project and referencing the datasheet Figure 31.

They are also implementing the Xilinx ZCU106 in their design and noticed on the Xilinx Evaluation board that the schematic for the TMDS181 slightly differs from the datasheet.

The customer is wondering if the Xilinx schematic circuit is okay as a reference and if we have recommendation for sink side application.

Thank you in advance for your help!

Best regards,

Errol

over 4 years ago

0 David (ASIC) Liu over 4 years ago

TI__Guru*** 139705 points

Errol

Are you referring to the external termination resistors on the TMDS181 output? The TMDS181 is designed to be HDMI spec compliant. The HDMI 1.4b and HDMI2.0 standards define a DC-coupled 3.3 V common mode interface. But the FPGA inputs more than likely require to be AC-coupled. When AC coupling between the TMDS181 and the FPGA, external termination has to be used to set the correct common mode for the TMDS181 output.

The use of the external termination produces a double termination and therefore will reduce the signal swing. the TMDS181 transmitter's voltage swing must be increased to compensate for the double termination.

Thanks

David

0 Errol Leon6 over 4 years ago in reply to David (ASIC) Liu

TI__Expert 5830 points

Hello David,

Yes, I am referring to the external resistor and inductor at the output of the TMDS181.

Thanks!
Errol

0 David (ASIC) Liu over 4 years ago in reply to Errol Leon6

TI__Guru*** 139705 points

Errol

Please see my previous response on the external resistor.

The ferrite bead inductor is there to filter high frequency power supply noise and make sure the noise is not coupling onto the TMDS output.

Thanks

David

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TMDS181: Hardware schematic design recommendation