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MSP430FR2522: Captive touch sensor pattern guideline for FPC(Flexible Print Circut).

Jeff Chen71
Expert 1345 points
Part Number: MSP430FR2522


Hi ,

      Customer layout captive touch  button on FPC board as below picture. The performance is so bad. I think it because the board is too thin cause the parastic cap too much.

  • They are asking  a layout guideline for  FPC board. 
  • Do we have other customer using captive touch  in FPC and success? 
  • Self  or mutual, which one is best for this application.

B.R.

Jeff Chen

  • 0
    TI__Genius 9570 points
    Hi Jeff,

    1. Because FPC is very thin, touch sensor is very close to ground plane and parasitic capacitance is extremely heavy. We usually recommend to use 8% ~ 10% hatched ground polygon pour.

    2. Yes, we have customers who use FPC touch sensor with CapTIvate.

    3. It is recommended to use self-mode button in FPC touch sensor design.

    Regards,
    Ling
  • 0 in reply to Ling Zhu2
    Expert 1345 points

    Hi Ling,

    1.Could you descript why you suggest self-mode button. What is the benfite then mutual mode .

    2.Should we need increase the captive touch pcb trace clearance for reduce the parasitic capacitance? Do you have suggestion about clearance? 

    Thanks

    B.R.
    Jeff Chen

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