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DS90UB935-Q1: EMI Challange

Evan Wang
Genius 9500 points
Part Number: DS90UB935-Q1

Tool/software:

Hi Team,

Hope you're doing well.

We're facing EMI issue on 1.6GHz band based on 935 + 954.

We use synchronous clocking mode.

=> For OEM/Project info, we can discuss through email.

I learn from other post that except for changing the layout, we might be able to change the VOD/SSCG/output slew rate to reduce the EMI.

Based on our current configuration, do you have any common suggestion on the SW/HW adjustment?

And I notice 954 has the SSC, is it adjustable? or the SSC is enabled by default?

Thank you. 

  • 0
    TI__Mastermind 24911 points

    Hi Evan,

    Thanks for reaching out with this question. Do you have details on the EMI failure encountered by your customer? How many dB are they failing by? If you could share the current results it would be appreciated.

    As you pointed out 954 has the option to accept a SSC oscillator, but this should be spread spectrum already from the oscillator rather than SSCG available on some newer devices where the deserializer generates the SSC profile. Could you confirm if the customer has tried a SSC oscillator yet?

    Best,

    Thomas

  • 0 in reply to Thomas Bejin
    TI__Genius 9500 points

    Hi Thomas,

    Thomas Bejin said:

    Thanks for reaching out with this question. Do you have details on the EMI failure encountered by your customer? How many dB are they failing by? If you could share the current results it would be appreciated.

    I will check with Customer on that.

    Thomas Bejin said:

    As you pointed out 954 has the option to accept a SSC oscillator, but this should be spread spectrum already from the oscillator rather than SSCG available on some newer devices where the deserializer generates the SSC profile. Could you confirm if the customer has tried a SSC oscillator yet?

    I think i misunderstand the meaning the the SSC, you mean the 954 don't have SSC but we can achieve that by choosing a oscillator with SSC already, am I right?

  • 0 in reply to Evan Wang
    TI__Genius 9500 points

    Hi Thomas,

    Due to confidential requirement, just send you the schematic and the EMI result we got.

    Please help to check those part.

    Thank you. 

  • 0 in reply to Evan Wang
    TI__Mastermind 24911 points

    Hi Evan,

    Thanks. And you are correct here, UB954 supports spread spectrum clock (from reference clock) but not spread spectrum clock generation. I will check the details in your email.

    Best,

    Thomas