TUSB546A-DCI: Audible noise coming from device

Eric S

Part Number: TUSB546A-DCI

We are experiencing some audible noise from the TUSB546A-DCI. I suspect it may be the ceramic capacitors. (I probed the board by sticking a straw in my ear and touching various areas.)

The data sheet indicates 75nF to 265nF should be used for AC Coupling, but it doesn’t mention the voltage rating or the preferred material.

We are using 100nF, 16V, X7R, 0402 parts. (GRM155R71C104KA88) Would this cause a problem and be the source of the audible noise? Have you seen this before and have any suggestions what else to check?

Thank you.

over 1 year ago

0 David (ASIC) Liu over 1 year ago

TI__Guru*** 141880 points

Hi,

I came across this Murata link, https://www.murata.com/en-us/support/faqs/capacitor/ceramiccapacitor/char/0020, that may explain the noise you are hearing coming from the capacitor.

Thanks

David

0 Eric S over 1 year ago in reply to David (ASIC) Liu

TI__Expert 5550 points

Thank you. Customer does understand piezoelectric effect, which is why he has stated the MLCC's as potential suspect. However, data frequency on those lines is not in sub-20kHz range (I don't believe), and the datasheet doesn't spec any particular materials or ratings for the AC caps... Was looking for feedback from experience if this is something we have actually seen before with this device, or if we have more specific recommendations for materials/ratings for these caps. He can certainly do trial & error experiments by swapping caps, but was hoping we can provide some additional direction.

0 David (ASIC) Liu over 1 year ago in reply to Eric S

TI__Guru*** 141880 points

Hi,

Are they sending any data when this issues happens? I have not seen this kind of issue before and typically we only specified the AC coupling capacitor capacitance, but not the type of material for the high speed link.

Thanks

David

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TUSB546A-DCI: Audible noise coming from device