TI Friends and Family,
We have a customer who might have a radiation path issue with the audio codec interface as this appears during the receive/standby mode test at TUV.
Therefore, we are curious if there is any SSC for the audio interface to help spread the power a little as they do not fail by too much.
The frequency is about 88MHz and the failing portion are the 2nd and 3rd harmonic of that.
The audio clock in to the AM57 is 22.5762MHz…
With the sniffer it was localized near the Audio Codec.
The AUD_MCLK sourced from the AM57 does have a series termination resistor which should soften the edges of that clock however we might assume internal to the codec there could be some PLL or other paths. We believe they are below 40.4dBm at 3m.
Ideally, first, we need to try to find the source of the radiation path/noise. The schematics may provide us a clue. And I’m assuming this is repeatable across more than one PCB. We are working on that part of the debug exercise.
Secondly, the suggestion of possibly utilizing the Spread Spectrum Clocking feature to help spread out the power may be a good one. I see per the TRM and a bunch of E2E posts that this is frequently done for USB and even HDMI communications but I have yet to find a clear reference for doing so via the audio interface.
Has anyone had any experience in doing something like this?
Root cause first would be ideal, but the SSC idea could actually help mitigate this in the interim while under test.
Any comments or input welcomed!
TY,
CY
