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MSP430FR2632: Is My Hatched Ground & Spacing Setup Correct for Capacitive Touch?

RAYAN SAYED
Prodigy 20 points
Part Number: MSP430FR2632


hi ti community 

I’ve set the capacitive-touch area with a 0.5 mm / 45° hatched ground.
Ground-to-trace clearance is 0.6 mm (taken as t/8), and electrode-to-ground spacing is 2.4 mm (taken as t/2).
The overlay material is 4 mm glass

  Layout 
image.png hatch details 
image.png
Could you please confirm if these values and this approach are appropriate for capacitive-touch design? 

  • 0
    TI__Mastermind 39895 points

    Hi,

    It is no problem. One suggestion is to slightly move this signal line. As it is fully under the ground, it will have a larger capacitance to ground. The sensivity will be influenced.

    ...

    Eason

  • 0 in reply to Eason Zhou
    Prodigy 20 points

    Thanks for the reply. I just want to confirm a couple of points: Do you mean the signal trace should not have any ground directly underneath it? In my 4-layer stack, Layer 2 is power and Layer 3 is normally a solid ground plane. For this design, should the Layer-3 ground also be hatched, or should I leave that area as no-fill under the touch signal? I’m also planning hatched ground pours on the FCU and BCU. Will this create any issues for touch sensitivity?

  • 0 in reply to RAYAN SAYED
    TI__Mastermind 39895 points

    More GND area will cause more capacitance between GND and sensor. 

    Besides, the sensitivity lies on both the Cbase (capacitance between GND and sensor) and Cchange (involved by human touch). From GND setting level, the better things is to remove the GND area as much as possible. 

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