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Strange behavior of TPS3705-33 when MR input is exposed

Denis Kotlar
Intellectual 820 points

I have a trouble with TPS3705-33 that seems to generate erratically reset when MR input is "exposed" (mean connected with PCB area where tactile switch will be mounted with trace that is less then 2" long). I made a short video of what is happening. I "fix" the problem with adding 47nF capacitor between MR input and ground. 

Please let me know if that is a right way or I should paid attention to something else. Thanks a lot.

(you can use "Copy video URL" on right-click menu and open it in a new browser tab if preview below is not correct)

  • 0
    TI__Genius 14245 points
    Hi Denis,

    Unfortunately at this time the video isn't working for me here or on youtube. However, if external noise is coupling onto the trace connected to the MR pin this could cause the device to reset erratically (depending on the noise imposed on that node). If placing a 47nF cap is enough to filter out the noise and it works for your application then it should be fine. There is no reason from the device's perspective that you can't put a small bypass/filter cap on the MR pin.

    -Kyle
  • 0 in reply to Kyle Van Renterghem
    Intellectual 820 points

    Thanks Kyle for quick response. It's strange that youtube video doesn't work for you. But it's more strange for me that MR input can be influenced by mechanical means (by tapping in proximity of MR tactile switch). I can imagine that electrical (or EM) noise could trigger such erratic behavior. Anyway, since simple solution with adding capacitor is fine, I'm closing this issue.

    Best regards,

    Denis