Question about using CYBLE-416045-2 module with capsense on top of a 4 layer board and the parts on back side of PCB

[Doorknob]

I need to layout a board using a CYBLE-416045-2 BLE module but i need to place my capsense buttons (5 of them) on top side of PCB and my components on the back side of PCB.

Can i do this in a way so the capsense will not be effected in a negative way.  I would like some direction on how i can do this with as little adverse affects as possible.  Could i  get some support with this type of application please.

Scott

[VenkataD_41 · Accepted solution]

Hi,

I hope all your components are present on the Layer 4 including the inductors and the BLE modules.

We recommend you to keep complete ground in Layer 3. This isolates the CapSense buttons from interacting with other components of the system.

On Layer 2, you can keep complete hatch pattern connected to ground/shield based on the requirement for liquid tolerance for your application.

On Layer 1, please keep hatched ground around the sensors. Please refer section 7.4 in the following application note for more details.

https://www.cypress.com/file/46081/download

Thanks

Ganesh

[Doorknob]

Thanks Ganesh ... i have read your application note you referenced but i was not clear if i could actually place parts under the capsense items directly and have the cap sense operated properly.  Thanks for helping me!!!

Scott

[Doorknob]

Ganesh ... on the application note i believe it says to hatch layer 4 ... this does not make sense to me.  Or did i just read it wrong?

Scott

[BragadeeshV]

Hi scclc_2272156​,

Any ground plane directly under the CapSense buttons or within 1 cm area is recommended to be of hatch pattern so that Cp formed is less. Other areas of the PCB can be solid ground.   A ground as suggested in between layers help in reducing the interference of the components underneath the capsense buttons in the bottom layer.

Regards,

Bragadeesh