How to protect Capsense keypad from ESD?

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AsDh_4015406
Level 1
Level 1
10 sign-ins 5 replies posted 5 questions asked

I am using Cy8c4025AZI-s413 controller. Overall thickness is 3.5mm . I am using Overlay as a acrylic.

So how can i protect PCB from ESD.

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1 Solution
Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hi AsDh_4015406​,

As Len mentioned, the thick overlay does provide protection. You can refer Section 3.2 in Getting Started with CapSense AN.

pastedImage_0.png

The sections that follow talks about other parameters to ensure ESD protection.

Best regards,
Hari

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Len_CONSULTRON
Level 9
Level 9
Beta tester 500 solutions authored 1000 replies posted

AsDh,

The acrylic overlay provides some protection from ESD.   The thicker the overlay the higher the voltage needed to 'arc' through the acrylic.  If an ESD arc occurs, the acrylic acts as a 'resistor' to limit the current going into the capsense input.

Cypress should have a design Application note to cover recommended layout and ESD protection measures.

You theoretically can add transient-suppression silicon devices on your inputs such as transorbs.  Hopefully there is a section on this in the Cypress App note.  The potential issue with any silicon devices attached to the input is that the input capacitance will be increased.   At best, you will have to adjust the tuning settings to accommodate this extra capacitance.

Len

Len
"Engineering is an Art. The Art of Compromise."
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Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hi AsDh_4015406​,

As Len mentioned, the thick overlay does provide protection. You can refer Section 3.2 in Getting Started with CapSense AN.

pastedImage_0.png

The sections that follow talks about other parameters to ensure ESD protection.

Best regards,
Hari

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Thank you so much to All

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