Errata - USB Host configuration resistor R56

We will be updating the MicroZed Errata document to include an incorrect value for R56 on Revisions B, C, and F01. This resistor is currently 1K but should be 10K for USB Host mode.

Moving forward, new MicroZeds will be built with this change. Since this is not a PCB change, we expect that the new revision will be Fxx, where 'xx' represents the BOM version. We are waiting hear back from manufacturing to know what that 'xx' number will be, after which the Errata will be updated.

Bryan

0 e14 Contributor over 12 years ago

Thank you for publicising this errata.

What would be the symptoms of a problem caused by a 1K resistor?

If the problems manifest themselves, what is the suggested remedy?
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0 bhfletcher over 12 years ago in reply to e14 Contributor

First, let me clarify by saying that we have not been notified of any failures in the field related to this. It was just something we discovered while doing a review.
The SMSC USB3320 datasheet calls this the Rvbus resistor. It is set to 1K-ohm or 10K-ohm depending on operating mode. For Host mode, it should be 10K-ohm. 1K-ohm is the setting for OTG. On MicroZed with Rvbus = 1K-ohm, if there was an overvoltage event > 12.9V on Vbus, then the existing 62mW resistor would be undersized.
Bryan
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0 e14 Contributor over 12 years ago

Thanks for the clarification and for sorting out the issue before it becomes a problem - the hallmark of a team that is on-the-ball and doing the Right Thing.

Can I suggest that adding a very brief explanatory note at the end of your first message would also have given you that kudos!
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