377KHz noise spike on UbiSwitch

– Copied from customer email –

I am getting a noise spike on 377kHz, on a sensitive acoustic instrument when connected to the UbiSwitch (regardless of Ethernet port). This is mostly going through ethernet lines but also through the supply.
Can you narrow it down to a specific component?

UbiSwitch powered and connected through Ethernet.

UbiSwitch powered but no connected on Ethernet

UbiSwich off.

– Copied from customer email –

Sorry false warning. It was a Ethernet cable too close to a transducer.
Extremely sensitive thus we are normally shielding all Ethernet wires.

I have done some more testing to be completely sure about the noise spike on 377kHz and its indeed emitting from the switch through the DC lines.

Nothing was connected to the Ethernet port. Just the switch powered on using the same lab supply. We are testing using the large motherboard you shipped with UbiSwitch.

Using a DC filter on our end removed the noise.

This is highly likely to be the main 3.3V regulator on the UbiSwitch module itself. This is a TPS54260DGQR that is running at 400KHz (not quite 377KHz, but it’s within 10%.

Looks like we may want to beef up the DC filtering on the power line. Can you confirm what DC filter you used?