FDC2212: Will the sensor work this way?

Hi,

Yes, it is called hot-swapping. It is not recommended to use a switch at the sensor.

Regards

Sharath.

Thank you for the reply. Could you please tell me the risk if I do this? Will this damage the chip or this will affect the sensor  value a lot?

Hello Sharath,

If it doesn't support hot-swapping, is there a way that I can use two electronodes for two channels? And could you tell me the risk?

Hi,

You can connect one electrode to each channel. Is there any reason why need analog switch to connect to the device? Please refer to the EVM for reference.

Regards

Sharath.

You can see from the schematic that the LC values are different. So we can sense different parameters. And what’s the difference between connecting one electro node and two electro nodes for each channel? In the Evm, I see there is one electro node in each channel.

In applications in which high sensitivity at close proximity is desired, the differential  configuration performs better than the single-ended configuration. In my application, I do prefer the differential  configuration. What if I let the device go to shutdown mode, then I swap channels using analog switch? Will this also affect the sensor? I also checked the TIDA-00509.  I think they are almost the same. Both are changing the electrode.

https://e2e.ti.com/support/sensors/f/1023/t/434641?Fdc2212-Capacitance-to-Digital

Hi,

Shutting down the device before switching to the other channel could be a potential solution. But, we generally do not recommend any components between the sensor capacitor and the surface mount capacitor. This analog switch will add additional parasitics that could interact with the oscillations and may result in unintended consequences. I recommend testing your setup thoroughly before moving on to the next step. 

Please refer to Fig 55 of the datasheet for differential configuration. Is this how you want to connect two sensor plates to IN0A and IN0B

Regards

Sharath.

Yes, it is. IN0A and IN0B both will connect a sensor plate.

I can see that C4 and C9 are different values. Is there any reason you chose different setup for the same sensor plates?

Regards

Sharath.

To generate different frequencies range for different parameters. Some parameters are more sensitive to 653K, while some are more sensitive to 6.5M.