Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

PSoC™ 4 Forum Discussions

Anonymous
Not applicable

Hi,in AN64846,Getting Started with CapSense,I'm confused about "support higher parasitic capacitances",I think that for small finger capacitance,it should support higher parasitic capacitances,which is in contrast with description in follow picture.

cy.png

So,how to calculate parasitic capacitances according to finger capacitance?

Another related question:What's the meaning of CMOD and how to chose it?

Thank you

Best wishes

0 Likes
1 Solution
ShanmathiN_06
Employee
Employee
25 likes received 10 likes received First like received

Hello,

If the parasitic capacitance (Cp) of your sensor is higher than 45 pF, then you would have to use manual tuning.

Typically, the capacitance added by finger (Cf) would be higher than 0.2 pF.

You design CapSense sensors in such a way that Cp is less and choose an overlay, such that the Cf would be high.

You can refer to PSoC 4 CapSense design

Cmod is required for the operation of CapSense to maintain AMUXBUS at a constant Vref.

Recommended value- 2.2 nF

You can refer to Section 2.3.2 of http://www.cypress.com/file/41076/download.

Thanks,
Shanmathi

View solution in original post

0 Likes
1 Reply
ShanmathiN_06
Employee
Employee
25 likes received 10 likes received First like received

Hello,

If the parasitic capacitance (Cp) of your sensor is higher than 45 pF, then you would have to use manual tuning.

Typically, the capacitance added by finger (Cf) would be higher than 0.2 pF.

You design CapSense sensors in such a way that Cp is less and choose an overlay, such that the Cf would be high.

You can refer to PSoC 4 CapSense design

Cmod is required for the operation of CapSense to maintain AMUXBUS at a constant Vref.

Recommended value- 2.2 nF

You can refer to Section 2.3.2 of http://www.cypress.com/file/41076/download.

Thanks,
Shanmathi

0 Likes