FDC2212: Shielding

user5866401

Intellectual 420 points

Part Number: FDC2212
Other Parts Discussed in Thread: FDC1004, FDC2214

Hello;

I use FDC2212, I try to measure two capacitance which are CU plane on a PCB. But capacitor interact each other.

There is two shielding concept releated on datasheet.

But I can not undestand How I use shielding when two capacitor are measured with a FDC2212.

I am trying to cancel interaction of two capacitor.

Any offer?

Best regards.

over 5 years ago

0 Kristin Jones93 over 5 years ago

TI__Genius 17440 points

Hello,

Can you share your schematic? I am a little confused by your setup.

Best Regards,

0 user5866401 over 5 years ago in reply to Kristin Jones93

Intellectual 420 points

Hello;

FDC circuit is based on datasheet.

The sensing electrod part is below. Single ended confuguration is used. Capacitor 1 is connected to IN0A Capacitor 2 is connected to IN1A.

Capacitor 1 and Capacitor 2 is CU plane which are on PCB electrod.

Aluminium encloser is grounded and whole pcb electrod is in encloser.

Best Regards.

0 user5866401 over 5 years ago in reply to user5866401

Intellectual 420 points

Hello;

The connection PCB electrod and FDC part is shown below.

Best Regards.

0 user5866401 over 5 years ago in reply to user5866401

Intellectual 420 points

Hello;

I saw a forum post about shielding.

Is that proper for passive shielding?

Best Regards.

0 user5866401 over 5 years ago in reply to user5866401

Intellectual 420 points

Hello;

And active shield.

Is that proper for active shielding?

Best Regards.

0 user5866401 over 5 years ago in reply to user5866401

Intellectual 420 points

Hello;

I read fdc1004 papers.

In my desingn I want to use shield ring.

Is the shielding concept is same both device?

What is your opinion?

Best Regards.

0 Kristin Jones93 over 5 years ago in reply to user5866401

TI__Genius 17440 points

Hello,

You have the correct configuration for active and passive shielding. The FDC1004's architecture is different from the FDC2214, so the shielding concept is a little different. The FDC2214 does not have a shield pin, which is why we recommend buffering the INxA signal and using this as the shield. You may find this blog post helpful for an explanation of the differences between the two architectures: e2e.ti.com/.../capacitive-sensing-which-architecture-should-you-choose

All of the shield configurations you showed in your last post will work with both the FDC1004 and the FDC2214. I agree that the shield ring would be the best approach for your application because it will reduce the fringe capacitance between the two copper sensors.

Best Regards,

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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FDC2212: Shielding