This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AM180x USB2.0 Device: Full speed signal integrity

Genius 5785 points

Hello,

We have a problem of AM180x USB2.0 device. We assembled thousands boards for production. Almost boards are fine, but a few boards are not good. They can't be recognized from Host PC via USB. They're "Unknown Device". I tried checking USB compliance test for them. The signal integrity test for full speed is failed even though almost test items are passed including signal integrity test for high speed. The test is "Upstream Full Speed Signal Quality Test". It looks like the width of pulse is short. I think the latter changing timing of logical level is so fast.

I've checked below. USB_REFCLKIN for USB PHY doesn't have jitter. Power supply sequence is good and also each power lane is in the recommended operating voltage. There is a common mode filter for USB and a variable resistor for ESD protection on DP and DM. Could you give me some advice?

Regards,
Kazu