TDP142: TDP142 maximum gain clarification required

Sivanantham S

Part Number: TDP142
Hi, I am using two TDP142 red river in my pcb.Trace length after red river to dp connectors is approximately 6 inches and cable length is 2 to 3 meters. So i have set 14.4 dB as gain for both ics. My question is will this highgain affect dp monitor? Regards, Sivanantham

over 4 years ago

0 David (ASIC) Liu over 4 years ago

TI__Guru**** 175751 points

Sivanantham

Do you have a block diagram you can share? What is the trace length from the DP source to the TDP142? My concern with the max 14.4dB gain being set for both redriver is that you are over-equalize the signal which could cause the DP link training to fail.

Thanks

David

0 Sivanantham S over 4 years ago in reply to David (ASIC) Liu

Intellectual 840 points

BLOCK DIAGRAM- TPD 142.pdf

Block diagram is attached. Kindly help ASAP.

0 David (ASIC) Liu over 4 years ago in reply to Sivanantham S

TI__Guru**** 175751 points

HI,

Thanks for the block diagram. Since the DP142 is a linear redriver which provides RX equalization, you would want to put both DP142 as close to the DP connector as possible (1 or 2in).

For example, if you put the A Port DP142 2in to the DP connector, the DP142 will help compensating for the 12in trace loss between the A port and the DP142, the A port will then compensate for the 2in trace insertion loss between the DP142 and the DP connector plus the DP cable.

Thanks

David

0 Sivanantham S over 4 years ago in reply to David (ASIC) Liu

Intellectual 840 points

Hi,

In current design, DP142 ICs are present in one card and both DP connectors are mounted in another card. So can i mount one more DP142 IC near to connectors?

Will it create any problem?

Please confirm.

Regards,

S.Sivanantham

0 Sivanantham S over 4 years ago in reply to Sivanantham S

Intellectual 840 points

Also kindly confirm the optimum placement of DP redriver.

0 David (ASIC) Liu over 4 years ago in reply to Sivanantham S

TI__Guru**** 175751 points

S.Sivanantham

Since the TDP142 is a linear redriver, I do not see an issue placing the additional TDP142 on the DP connector board. You want to place the TDP142 closer to the DP connector and let the TDP142 RX equalizer to compensate for the 10in trace loss as much as possible.

Thanks
David

0 Sivanantham S over 4 years ago in reply to David (ASIC) Liu

Intellectual 840 points

Hi David,

Thanks for confirmation. What gain i can set for the redriver?

Kindly recommend.

Regards,

S.Sivanantham

0 David (ASIC) Liu over 4 years ago in reply to Sivanantham S

TI__Guru**** 175751 points

S.Sivanantham

The gain depends on the insertion loss of the 10in trace at the Nyquist frequency of the data rate, plus via, connector, etc. For example, if we assume the trace insertion loss is 0.5dB/in at 4.05GHz (HBR3 8.1Gbps), then 10in trace will have 5dB loss and you can set the DP142 EQ gain around 4.9dB (refer to Table 2 in the TDP142 datasheet).

Thanks

David

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TDP142: TDP142 maximum gain clarification required