FDC2214EVM: Capacitance value vs. drive current

Alex Semeniuk

Part Number: FDC2214EVM
Other Parts Discussed in Thread: FDC2214

Hello,

I've noticed that as I set larger drive current on the EVM, the capacitance value increases.

Why does it happen? Shouldn't capacitance remain the same, since distance to the object and the plate size are the same?

Please explain,

Warm regards,

Alex

over 6 years ago

0 Bala Ravi over 6 years ago

TI__Expert 6625 points

Hi Alex,
We've got your request. We will get back to you as soon as possible.

Best Regards,
Bala Ravi

0 Bala Ravi over 6 years ago in reply to Bala Ravi

TI__Expert 6625 points

Hi Alex,
Please check the oscillation voltage at INAx pin with respect to GND and make sure it falls between the range of 1.2V to 1.8V. This will ensure that your drive current is correct and results in best measurement accuracy. Please refer to the sensor drive current application note: www.ti.com/.../snoa950.pdf, the drive current settings for FDC2214 is similar to drive settings for LDC161x/131x, so the instruction in the application note will work.

Best Regards,
Bala Ravi

Please click "This resolved my issue" button if this post answers your question

0 Alex Semeniuk over 6 years ago in reply to Bala Ravi

Intellectual 300 points

Hello Bala Ravi

Thank you for your reply.

Indeed, at high current value, the Vosc was greater than 1.8V.

So whatever sensor size and wire length we select, it is crucial to have Vosc<1.8V, correct?

Thank you,

Alex

0 Bala Ravi over 6 years ago in reply to Alex Semeniuk

TI__Expert 6625 points

Hi Alex,
That's correct below 1.8V and above 1.2V.

Best Regards,
Bala Ravi

Please click "This resolved my issue" button if this post answers your question

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FDC2214EVM: Capacitance value vs. drive current