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msinger
msinger
Associate
January 9, 2014
Question

STMTouch & Shield

  • January 9, 2014
  • 1 reply
  • 576 views
Posted on January 09, 2014 at 21:26

What exactly does marking a pin as SHIELD do?

#tsi-stmtouch
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    1 reply

    Thierry GUILHOT
    Thierry GUILHOT
    Technical Moderator
    January 16, 2014
    Posted on January 16, 2014 at 22:25

    The shield pin is used to drive an active shield (also called driven shield) plane.

    The principle of a driven shield is to drive the shield plane with the same signal as the

    electrode. There are several advantages of using a driven shield instead of a grounded one:

    o The parasitic capacitance between the electrode and the shield no longer needs to be

    charged. This offers an optimum sensitivity.

    o A driven shield is useful for certain applications where shielding may be required to:

      – Protect the touch electrodes from a noise source

      – Remove touch sensitivity from the cable or track between the electrode and the

    sensing MCU.

      – Increase system stability and performance when a moving metal part is close to

    the electrode.

    If you need further information, I invite you to have a look to the AN4312.

    What exactly does marking a pin as SHIELD do?

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