MSP430FR2512: Maximum separation needed for Capacitive Touch detection?

Hello Walter,
seeing the picture of your application, I understand your post in the way, that there will be a certain gap between the casing and the capacitive sensing electrodes on the PCB, as all the components are as well on the top side of the PCB.
Now this is something we recommend to avoid in any case, and this recommendation is not related to the MSP430 capacitive sensing technology, but related to capacitive sensing as such, and the behavior of electric fields. One should always avoid air gaps between electrodes and the touch surface. There is some theory of electric fields in matters and on transitions between matters with different dielectric constants.
You can find more detailed explanations on these topics in the CapTIvate Technology Guide, which gets installed in combination with our free of charge CapTIvate Design Center ( www.ti.com/.../mspcaptdsnctr ) , but to cut the story short, the solution needs to be to bridge in some way the gap between touch surface and the electrodes.
There are two options:
1. Either you use some kind of conductive material to bridge this gap, usually the better solution, giving better and more reliable performance.
2. Bridge the gap using the same material as the casing, or other material with sufficiently high dielectric constant.

Best regards
Peter

Hi Peter,

Thanks for giving us heads up about this problem. For the development board of boostxl_capkeypad demo, I think in this board we have seen about 3mm space can work.

software-dl.ti.com/.../ch_evm_boostxl_capkeypad.html


Regards,
Walter

Hello Walter,
in terms of the thickness of the overlay itself, dependent on the overlay material, design of the sensing electrodes, and potentially other parameters, our technology can work with e.g. glass overlays of even 8mm and more.
Please consider checking on the HW design related topics our CapTIvate ™ Technology Guide chapter "Design Guide". There you can find also very detailed explanations on these topics, related to overlay material, and my explanation in my previous post. Many thanks in advance.
In case you need further support, please let us know. In case not, please close the thread.

Best regards
Peter