DS90UB953-Q1: Evaluation methods for communication robustness under environmental stress conditions

Hello Yamamoto-san,

The main criteria that must be met are the Insertion Loss and Return Loss characteristics on the high-speed path, between the Ser and the Des. We have a different Channel Specs document, depending on which deserializer you are using in your system.

This E2E was posted under the 953, but are you using an FPD3 or FPD4 generation deserializer? And do you have a local TI FAE supporting you, who can help you get access to NDA documents?

If you are using an FPD3 generation deserializer, then you can refer to this document for the expected IL/RL targets for your design:

https://www.ti.com/lit/an/snla224b/snla224b.pdf

See Section 4.1 Channel Requirements

If you are using an FPD4 deserializer, you would need to request access.

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If you are meeting these design targets, then TI offers a number of diagnostics tools. The MAP tool for an FPD3 device and the EOM tool for FPD4 devices. These will evaluate the link margin. We typically expect customers to put their systems under worst-case conditions (e.g. high temp and high current draw) and then use these tools to evaluate their worst-case margin and verify that it is still within the limits set by TI, to ensure error-free video transmission.

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We also have a number of diagnostics registers in the deserializer and serializer that can detect errors in the Forward Channel and Back Channel directions.

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The tools that I can recommend you depend on which SerDes devices you are planning on using, so if you have a device in mind, I can provide more detailed suggestions.

Best,

Justin Phan

Thank you for your detailed explanation.

We are currently evaluating communication quality assessment methodologies under environmental stress conditions rather than a specific SerDes product design. Therefore, we are not yet targeting a specific FPD-Link III or FPD-Link IV device.

At this stage, our objective is to better understand how communication robustness is evaluated in real automotive development and validation activities. We do not currently require access to NDA documents.

I have two additional questions:

1. During environmental stress testing (such as temperature cycling, high-temperature operation, humidity exposure, or condensation testing), do automotive  　customers typically monitor link margin (MAP/EOM) and diagnostic indicators continuously throughout the test?

　Or is it more common to evaluate communication quality only before and after the environmental test?

2. Is link margin degradation generally observed before actual communication errors occur under environmental stress conditions?

In other words, is link margin commonly used by automotive customers as an early-warning indicator to identify potential communication quality degradation or reliability concerns before communication errors become visible?

We are particularly interested in understanding whether link margin is used not only as a pass/fail metric, but also as a predictive indicator for communication robustness and long-term reliability.

Thank you for your support.