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Original question:

DS90UB953-Q1: proper setup for EMI and Spread Spectrum

DS90UB960-Q1: How to select spread spectrum for deserializer?

An
Intellectual 840 points
Part Number: DS90UB960-Q1
Other Parts Discussed in Thread: TDA4VM

Hello TI experts,

I would like to confirm how to select spread spectrum for deserializer DS90UB960.

Questions:

What are the efforts if we use spread spectrum for deserializer DS90UB960? Can it improve EMI results?

Additional, will it affect the quality of the RF signal? That's a point I focus on.

What's you suggestions? Do you recommend users to use or not to use for a general design?

Thank you in advance.

  • 0
    TI__Mastermind 23785 points

    Hello An, 

    I edited the posted question to focus on the DS90UB960 as we are unable to discuss NDA devices on the public forum. For questions pertaining to NDA devices, please reach out to your TI sales representative. 

    SSC oscillators can be used by the 960 so long as the oscillator meets specifications. These specification are listed in section 7.4.4 REFCLK: 

    SSC is used to mitigate EMI/EMC issues and has been observed to improve results. The change is largely system dependent and we do not typically suggest one over the other. 

    To enable spread spectrum you must use the serializer in synchronous mode and apply a spread spectrum REFCLK to the deserializer side which will have the effect of spreading both the forward and back channels for the SERDES pair.

    Please let me know if there are any additional questions. 

    Best,

    Zoe

  • 0 in reply to Zoe Bison
    Intellectual 840 points

    Hello Zoe，

    Thank you for your quick reply.

    I can understand EMI/EMC issues are largely system dependent and spread spectrum will do improvement very likely.

    However, I would also like to confirm if spread spectrum will bring some adverse effects, such as can it make signal transmission more prone to errors compared to no spread spectrum(we use TI953&TI935), or may it consume more computing power from SOC(we use TDA4VM), or something else？

  • +1 in reply to An
    TI__Mastermind 23785 points

    Hello An,

    Regarding the FPD-Link devices, the devices should not pull more power or make the transmission more prone to errors when using spread spectrum clocking.

    Using spread spectrum clocking could potentially change insertion loss and return loss results. The concern here is simply to ensure the channel specifications are still met. 

    Best,

    Zoe