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DS90UB964-Q1: Application problems of chips

Tonyx.wu
Genius 4015 points
Part Number: DS90UB964-Q1

Deserdes DS90UB964 and Serdes DS90UB953 are currently used in some projects. During EMC experiments, 1.6G is found to exceed the standard (required to be level 5). At present, it is related to these two chips. Do you have any suggestions for improvement? Thank you for your support

Please help to confirm some other questions. We know that the spread spectrum application will significantly improve RE testing

1. Does the external reference clock of the DS90UB964 support spread spectrum?

2. DS90UB953 is our current external reference clock. Can the external reference clock support spread spectrum?

3. The spectrum analyzer test shows that if the 953 internal clock is used, it will be much better than the external crystal oscillator. Is there any risk if we change to the internal reference clock? What should I pay attention to

4. Referring to some data of TI, it is found that the spread spectrum application of external reference clock is basically in Deserdes, but our actual test shows that most of the sources are in Serdes. Is it effective to add spread spectrum in Deserdes in this case?

  • 0
    TI__Guru** 108550 points

    Hello Tonyx,

    Tonyx.wu said:
    Deserdes DS90UB964 and Serdes DS90UB953 are currently used in some projects. During EMC experiments, 1.6G is found to exceed the standard (required to be level 5). At present, it is related to these two chips. Do you have any suggestions for improvement?

    • EMC is a system level specification and will depend on housing, shielding, PCB layout, component selection.
    • The following techniques are recommended at the system level to improve EMC performance:
    – Use of metal shielding
    – Good grounding techniques
    – Proper differential layout of PCB traces
    – Trace impedance control

    Tonyx.wu said:
    Does the external reference clock of the DS90UB964 support spread spectrum?

    The UB964 does not support Spread Spectrum functionality!

    Tonyx.wu said:
    . DS90UB953 is our current external reference clock. Can the external reference clock support spread spectrum

    No, you can't use an external Oscillator with SSCG connected to the UB953. 

    Tonyx.wu said:
    The spectrum analyzer test shows that if the 953 internal clock is used, it will be much better than the external crystal oscillator. Is there any risk if we change to the internal reference clock? What should I pay attention to

    Unfortunately using the Internal AON clock mode is not supported when using the UB953 in Backward mode, i.e., pairing the UB953 with a DVP DES such as UB914A, UB934 or UB964.

    Tonyx.wu said:
    Referring to some data of TI, it is found that the spread spectrum application of external reference clock is basically in Deserdes, but our actual test shows that most of the sources are in Serdes. Is it effective to add spread spectrum in Deserdes in this case?

    Adding an SSCG Oscillator at the DES side in your use case does not help, because you are not using the Synch mode.