TDP158: NO HDMI output, please help to review the schematics.

yunfeng wang

Part Number: TDP158
Other Parts Discussed in Thread: TS3DV642, TMDS181

Tool/software:

I designed a motherboard based on the TDP158, currently the DDC protocol is successful when going straight through with the external connector, but there is no HDMI output? can you help to reviewthe schematic?

Thank you

5 months ago

0 yunfeng wang 5 months ago

Prodigy 50 points

vcc and vdd timing are as follow. PRE,EQ1,EQ2,SLEW,TERM, are NC.

and I have added a watchdog chip to control the OE pin. delay time:210ms.

power timing

0 yunfeng wang 5 months ago in reply to yunfeng wang

Prodigy 50 points

Sorry it's a Reset circuit Chip not a wathdog.

0 David (ASIC) Liu 5 months ago in reply to yunfeng wang

TI__Guru**** 180061 points

Hi,

Can you please share your schematic? Is HPD_SNK being driving high by the monitor?

Thanks

David

0 yunfeng wang 5 months ago in reply to David (ASIC) Liu

Prodigy 50 points

Hi David, thank you for your support.

I have sent you the schematic via private message and updated the capacitors in the power supply circuit to match the power supply timings.

When testing the board, the PC has recognized the monitor, so DDC was successful.

But the monitor said it is not receiving HDMI signal.

0 David (ASIC) Liu 5 months ago in reply to yunfeng wang

TI__Guru**** 180061 points

Hi,

Looking at the schematic, you have a HDMI IN - TS3DV642 - TS3DV642 - TDP158 signal path. But the HDMI is a DC coupled signal, you will have to put 50ohm to 3.3V termination between the TS3DV642 and the AC coupling capacitor of the TDP158 input.

Because this is a connection between two HDMI ports, no pullup resistor is needed on the DDC bus.

Thanks

David

0 yunfeng wang 5 months ago in reply to David (ASIC) Liu

Prodigy 50 points

Hi David Thanks for your support, I have updated the schematic, is this what you mean?

By the way, Do you have a better chip recommendation for this application?

0 yunfeng wang 5 months ago in reply to David (ASIC) Liu

Prodigy 50 points

And If I add the 50ohms, Is this Ok for the other path which is to the CPU?

0 David (ASIC) Liu 5 months ago in reply to yunfeng wang

TI__Guru**** 180061 points

Hi,

If the other path is CPU, then the 50ohm termination needs to be moved to Side A to HDMI-IN MUX since CPU does not need the 50ohm termination. Let me review your latest schematic and I will provide my feedback.

Thanks

David

0 yunfeng wang 5 months ago in reply to David (ASIC) Liu

Prodigy 50 points

Hi David,

I have sent you a private message. Is it OK? Thank you.

0 David (ASIC) Liu 5 months ago in reply to yunfeng wang

TI__Guru**** 180061 points

Hi,

I provided my review comment in the private message.

Thanks

David

0 yunfeng wang 4 months ago in reply to David (ASIC) Liu

Prodigy 50 points

Hi David

I have drawn a new schematic, and sent it to you via private message. could you please help to review it?

Thank you.

0 David (ASIC) Liu 4 months ago in reply to yunfeng wang

TI__Guru**** 180061 points

Hi,

I provided my review comment in the private message.

Thanks

David

0 yunfeng wang 4 months ago in reply to David (ASIC) Liu

Prodigy 50 points

Hi David, Thank you for your help.

And can I use the input detection function of TMDS181? when I use it in the sink side application.

+1 David (ASIC) Liu 4 months ago in reply to yunfeng wang

TI__Guru**** 180061 points

Hi,

Yes, you can use the TMDS181 SIG_EN function. The SIG_EN pin enables the signal detect circuit that provides an automatic power-management feature during normal operation. When no valid signal is present on the inputs, the device will enter standby mode.

Thanks

David

0 yunfeng wang 4 months ago in reply to David (ASIC) Liu

Prodigy 50 points

OK, Thank you David,

The last thing I would like to confirm is regarding the HDMI 2.1 interface circuit. It includes capacitors and a MOSFET, and it is compliant with HDMI 2.0 and HDMI 1.4.

If I remove the MOSFET and resistors, and operate in HDMI 2.0 or 1.4 mode, can the TDP158 still receive the HDMI signals correctly?

+1 David (ASIC) Liu 4 months ago in reply to yunfeng wang

TI__Guru**** 180061 points

Hi,

HDMI2.1 allows the output to be either DC coupled or AC coupled while HDMI1.4/2.0 only allow output to be DC coupled. When a HDMI2.1 source is AC coupled, it still needs to meet the DC coupled common mode voltage compliance testing requirement, so the termination plus the MOSFET was implemented to meet this common mode voltage testing requirement.

But DP158 is an AC coupled input, it will not work without AC coupling capacitor. It also does not need the external termination network with the MOSFET since it is already internally terminated.

Thanks

David

0 yunfeng wang 4 months ago in reply to David (ASIC) Liu

Prodigy 50 points

OK Thank you David, I will use TDP158 for my HDMI1.0/1.4/2.0 application. and remove the terminal network.

Interface

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TDP158: NO HDMI output, please help to review the schematics.