AM6422: Changing SD Card frequency

Christian Kohler25

Part Number: AM6422

Tool/software:

Hi.

We have some radiated emission peaks which are clearly related to SD-Card (HS mode, 50MHz)

For testing, I want to slightly reduce the SD-Card frequency, so that there is no "peak overlapping" in the radiated spectrum with other interferers.

Is it possible to change the PLL2_HSDIV_clkout2 divider from 10 to 11 to get 180MHz base frequency instead of 200MHz?

The divider factors for the SD-Host controller remain unchanged, so a High-speed card should be clocked with 180MHz/4 = 45MHz, not 50MHz

Is this possible?

Are there better options to slightly reduce the SD-frequency available?

Thank you,

Christian

0 Stanislav Stilyanov 3 months ago

Hi Christian,

I'm looking into this. Meanwhile, would like to know if any PCB updates are an option for you?

Stan

0 Christian Kohler25 3 months ago in reply to Stanislav Stilyanov

Hi Stan.

Thanks a lot. We try to prevent a PCB change if possible.

regards,

Christian

0 Stanislav Stilyanov 3 months ago in reply to Christian Kohler25

Christian, sorry for delay.

Te below register has a divider for that clock:

You can use it during debugging. I think that 45 MHz vs 50 MHz will have a little impact and you could need to experiment with lower frequencies.

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