Touchpad pcb design

[BhSa_4078721]

Hi,

I am going to design the layout for touchpad using cypress controller with 4 layer.

And I have the query for layer stack for touchpad. Currently I am going with following layer stack

L1 - Capsense touchpad diamond (electrode)

L2 - electrode trace with hatch ground

L3 - hatch ground pour

L4 – components with hatch ground

Please check and let me know that is this should be flow of layer stack.

[Hari · Accepted solution]

Hi @BhSa_4078721,

Are you planning on using mutual cap (CSX) touchpad or CSD? The difference between the two are:

Faster scanning time in CSD touchpad vs multi-touch in CSX (detection of more than one finger is supported in CSX)

The current configuration will work for CSD touchpad, but for CSX, the ground layer underneath the touchpad will cause a reduction in signal. So, if CSX is used, then it is recommended not to have hatched ground on layer 2 and to have hatched ground instead of solid ground in layer 3. 

Best regards, 
Hari