Part Number: TMDS361B
I have a customer using the TMDS361BPAGR to bring in 3 HDMI signals to a single HDMI receiver chip Analog Devices ADV7611. When he sent his product through HDMI compliance he had one failure when they ran the HDMI Sink Jitter test 8-7 at 27Mhz (480P resolution). The console passed testing at higher resolutions of 720P and 1080P. This was done using a “TYPE 2 Cable Emulator” that adds skew into the signal. Although he suspects the issue is at the ADV7611 side of the design, there is potential the TI part is contributing to the failure. He has had several calls with the compliance lab and Analog Devices on this and there were some questions that came up on the TI part. Could you please take a look at these questions below?
Thank you for your consideration!
Unfortunately, we do not have the RX jitter tolerance compliance report for TMDS361B.
Can they share their jitter tolerance report with us? If jitter tolerance is passing at higher data rate, I would expect it to pass at lower frequency as well.
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In reply to David (ASIC) Liu:
I believe that this might be what you are looking for. Do we have an eval board they can test with?
In reply to Jarrett:
Are they able to pass the test without the injected jitter (turn the jitter off)?
Does the sink support 27MHz clock frequency?
Yes, the board supports 27Mhz for 480p60 operation. When the jitter was applied for this resolution our board could not lock on the TMDS clock. We have been working on some register setting changes to the ADV7611 using the same values their evaluation kit had when it went to be tested for compliance. Some registers are related to equalization that would be appropriate for an HDMI cable, while our application has just PCB traces from the TI chip to the ADV7611, so we are not certain if there will be adjustments needed for the equalization values. We will be shipping the console back to the lab for a 2 hour consulting test to see if we have resolved the issue. We will also be logging information in case it still fails.
In reply to Steve Griffin:
Waiting feedback from customer
In reply to Brian Zhou:
The console was retested on 8/30/19. It still has a failure at 480P. The lab comment on this is:
When I look at section 8-6 of the HDMI 1.4a testing spec, it appears to show that a 0.4Tbit skew would still be acceptable. I only see the lab tested at 0.6Tbit of skew, so I have sent in a question about the 0.4Tbit.
Do you see the failure if the jitter is off?
The problem only shows up while jitter is applied for a 480P resolution. There are no issues when jitter is not applied. There are also no issues if at 720p or 1080p with or without jitter applied.
If the problem only shows up when jitter is applied, then I don't believe this is a equalizer issue.
The TMDS361B will not clean up the jitter, so we need to take a look at the ADV7611, to see if it has a CDR or PLL and change the bandwidth to better track and filter out the jitter.
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