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LP5562: little steps on SDA waveform

George Zhao
Intellectual 1635 points
Part Number: LP5562

Hi team,

My customer found some little steps on the waveform of SDA signal of LP5562, as shown below:

I reviewed their PCB and found a 90 degrees angle in the routing as the yellow circle shows in below. 

I have very little experience so I need to check with you on following:

  • is the waveform normal? As customer reflected their system is working good, but want to make sure if it has potential risk.
  • what maybe causing this steps? could it be the 90 degrees routing?

Thank you very much!

George

  • 0
    TI__Genius 12915 points

    Hi George,

    This is not a normal waveform. The little pulse looks like having a constant duty cycle. Could customer send a long time low level signal to see if it still exist? Minimum input high level is 0.2 VEN. If high level of abnormal pulse was far away from 0.2 VEN, I think it should not trigger wrong input signal.

    To be honest I am also not know where this noise comes from. Since SDA is the input pin of LP5562, I think it should be injected by LP5562. If the pulse have a constant duty cycle, it may comes from the device which worked at the same duty in the system.