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LP5521: Acknowledge on SDA

Norbert Kailan
Prodigy 50 points
Part Number: LP5521

The address is sent MSB considering the pinning A0 A1 both to ground, when wanting to write: 0x64.

There is no valid acknowledge. The acknowledge at the ninth clock is going only less 20% down instead at least 80% to be recognized.

Is the pin defect? The I2C SDA pin where this happens goes down to -1.7 V for about 50 ns when switching from high to low. Could this have damaged the SDA pin or is this 20% pull down not an intended acknowledge?

I would send you an oscilloscope Picture if possible.

Sorry for Trouble and thank you in advance!

  • 0
    TI__Genius 14295 points
    Hi. Norbert,

    Voltage below -0.3V on logic pins could demage the pin even for a short time according to datasheet.

    I suppose the acknowledge is good before, is this correct?

    Please send me the picture if you can.

    Thanks.
    Regards,
    Kenneth
  • 0
    Prodigy 50 points

    Hi  Kenneth,

     

    thank you very much for this quick and friendly answer.

     

    I am happy to send you the pictures.

    Connections:

    No, sorry the SDA acknowledge did never come better than shown below. But the peaks were from the start and the peak situation is shown in below picture: Red is SDA, Blue is SCL.

  • 0 in reply to Kenneth Du
    Prodigy 50 points
    The pullups are 4.7k. The Picture was not uploaded by mistake and was just a screenshot.
  • 0 in reply to Norbert Kailan
    TI__Genius 14295 points
    Hi, Norbert,

    The ack signal is not able to be recognized and it seems internal circuit is wrong.

    Please try using another good unit to compare and confirm whether the internal circuit is demaged.

    Thanks.
    Regards,
    Kenneth
  • 0 in reply to Kenneth Du
    Prodigy 50 points

    Hi Kenneth,

    thank you for your answer.

    Unfortunately we have only 2 boards and on both same signal situation. The peaks were also from the start as visible. Isn’t it, and sorry that I still have something to ask, that these peaks need to get eliminated anyway? The peaks to 5 volts I have seen also in other and UART applications. But those under 0 volt not so much. For being sure to stay in specified area, we should change this situation, isn’t it?

    Best regards and thanks  Norbert

    Norbert Kailan extern at Getinge

  • 0 in reply to Norbert Kailan
    TI__Genius 14295 points

    Hi, Norbert,

    The peaks under 0 volt is too large and exceed -0.3V. This may causes porblem for internal circuits.

    Would you help to eliminate it and try again?

    Please let me know if this solves your problem.
    Thanks.
    Regards,
    Kenneth

  • 0 in reply to Kenneth Du
    Prodigy 50 points

    Dear Mr. Kenneth,

    the problem was, that our controller kept the acknowledge high because open drain on SDA was not enabled. I am sorry, I thought that would be done and I did miss that.

    The driver works properly even with these Peaks!!

    One driver on one board is still crashed. Should we put a protection to reduce the Peaks for long term usage or is that irrelevant? Please answer even when I pose the issue as resolved!

    Sorry for the effort and thank you very much for your HELP!