TDP158RSBEVM: About pullup register on IN_D/IN_CLK.

teritama

Expert 1570 points

Part Number: TDP158RSBEVM
Other Parts Discussed in Thread: TDP158

Hi team.

In user's guide, pull up register(49.9Ω) is connected to HDMI Rx pin and AC coupling capacitor.

Is this because it is necessary as HDMI specifications?

Or because of impedance matting?

In addition, pull-up register is connected to Board 3P3V, is it because highest voltage is Board 3P3V in this board?

best regards

teeritama

over 3 years ago

0 David (ASIC) Liu over 3 years ago

TI__Guru*** 139305 points

Teeritama

The TDP158 is a AC-coupled to HDMI level shifter. If connected to a DC-coupled HDMI source, then the pull-up resistors to 3.3V is required and mimimic a HDMI RX termination.

Thanks

David

0 teritama over 3 years ago in reply to David (ASIC) Liu

Expert 1570 points

David

thank you for quick reply.

I understood if this device is AC-connected, pull-up resister is not necessary.

Is it right?

In addition, how do you decide the value of pull-up resister's value=49.9Ω？

best regards

teritama

0 David (ASIC) Liu over 3 years ago in reply to teritama

TI__Guru*** 139305 points

Teritama

Correct. If it is a AC-coupled HDMI source, then the pull-up is not needed.

The selection of the termination resistor depends on the DC-coupled HDMI TX driving capability. The 49.9ohm termination network mimics a typical HDMI sink termination.

Thanks

David

0 teritama over 3 years ago in reply to David (ASIC) Liu

Expert 1570 points

David

Thank you for reply.
I understood.

best regards

teritama

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TDP158RSBEVM: About pullup register on IN_D/IN_CLK.