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DS90UB954-Q1: Quality check of differential input signal in actual system

Tomoaki Yoshida91
Genius 5255 points
Part Number: DS90UB954-Q1

Hi team,

Our customers are in the process of deciding waveform quality verification methods in actual systems.

We found that jitter can be monitored with CMLOUT, but the signal amplitude can not be monitored with CMLOUT.
In order to check the input signal amplitude, is there only way to directly monitor the RIN pin?
In that case, is the criteria of the differential input signal over 80mV?
They are studying how to guarantee the waveform quality with actual system.
Please tell me if there are other methods.
Best regards,
Tomoaki Yoshida
  • 0
    TI__Genius 10475 points
    Yoshida-san,
    The CMLOUT is the buffered loop-through version of the signal after equalization so cannot be used to measure the input voltage amplitude.
    This spec is for the minimum input signal amplitude seen at the RX input so measured at the RIN+/-.
    You can also measure the forward channel eye amplitude at the output of the serializer and then apply the channel attenuation to account for the channel loss to arrive at what the RX would see.
  • 0 in reply to Palaniappan Manickam
    Genius 5255 points
    Hi Palaniappan-san,

    Thank you for your support.
    I understand that.

    I have an additional question.
    When our customer is monitoring CMLOUT, they stop entering CSI-2 input.
    I think that the input of CSI-2 does not affect the opening of Eye, is this the correct measurement method?

    Best regards,
    Tomoaki Yoshida
  • 0 in reply to Tomoaki Yoshida91
    TI__Genius 10475 points
    Yoshida-san,
    The 954 will send output data on the CSI when there is data available to send out. If there is no data to send it will follow the MIPI CSI-2 spec and go into the low power state.