FDC1004: Switch for Capacitive Inputs

Art Mecina

Part Number: FDC1004
Other Parts Discussed in Thread: PCA9544A

Hello Guys,

Our customer is using the FDC1004 as a liquid level sensor, similar to the EVM. His design requires 3 separate sensors. He knows that he can use 3 FDC1004s and switch the I2C bus using a PCA9544A, but the FDC1004s are expensive.

We are hoping if you can recommend if there is a part that would work to switch the CIN inputs so he can use one FDC1004 for three electrode pairs?

Thanks in advance!

Art

over 4 years ago

0 Mekre Mesganaw over 4 years ago

TI__Expert 7495 points

Hi Art,

We are currently looking into this. We should have more details on this by tomorrow.

Regards,

Mekre

0 Mekre Mesganaw over 4 years ago in reply to Mekre Mesganaw

TI__Expert 7495 points

Hi Art,

We recommend using 3 FDC1004s in this scenario; however, if there is a constraint on using 3 FDC1004s, it might be possible to MUX the FDC1004 as long as you aren’t using the repeat mode of operation. The following post has more info on this:

https://e2e.ti.com/support/sensors/f/sensors-forum/808537/fdc1004-demultiplexing-signals-from-multiple-sensors-to-fdc1004-channels?tisearch=e2e-sitesearch&keymatch=fdc1004%252520multiplex

Please note though that using the external MUX is not a typical option, and this is not something that we have tested and verified on the FDC1004 ourselves. Also, a MUX can have a complicated resistance versus VIN response when it is conducting. In addition, the MUX may add additional capacitance that can result in erroneous readings. The capacitance from the MUX and its VIN response should be taken into consideration if you try this approach.

Regards,

Mekre

Sensors

Sensors forum

FDC1004: Switch for Capacitive Inputs