• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 20 subscribers
  • Views 1224 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

CDCE72010 input hysteresis

David Burton
Expert 1330 points
Other Parts Discussed in Thread: CDCE72010, CDCLVD1208

Hi,

The ref and VCXO inputs have a hysteresis option, but I don't see any discussion of exactly what the parameters of the hysteresis are.  Is there some guidline on when hysteresis should be used and not?

Thanks.

  • 0
    TI__Expert 4150 points

    Hi David,

    the hysteresis function establishes a small voltage threshold (tens of mV) to prevent the input from picking up noise when the input is not driven. For example, if the input is AC coupled and not driven, the receiver input self-biased will establish the working common mode voltage, and any noise coupling into this undriven input could cause the input stage to detect a signal and switch on it. To prevent this switching, hysteresis is offered on the input.

    The disadvantage of hysteresis is that it adds a small amount of noise to the input. Therefore, systems not concerned about undriven inputs will probaly prefer to disable hysteresis.

    If you drive the CDCE72010 from the CDCLVD1208, and the input is DC coupled, you should probably disable hysteresis if you are concerned about best possible overall jitter. However, the problems you have seen about not having any output signal on the CDCE72010 should be indifferent to whether or not hysteresis is enabled or disabled.

     

    Best regards. Falk Alicke