FDC1004: Added capacitors to VDD, and to SHIELD

Richard Wu2

Part Number: FDC1004

We will be using the FDC1004 in an application that will be using around 40 sensors.

1. What affect does adding the 1 uF and 0.1 uF capacitors to VDD?

2. In the FDC1004 user guide, the schematic shows the shields being shorted with 51 pF capacitors. If we are not using the shield pins, is it still necessary to use the capacitors?

Thank you,

Richard

over 6 years ago

0 Kristin Jones93 over 6 years ago

TI__Genius 17440 points

Hi Richard,

1. These are bypass capacitors intended to filter high frequency noise to ground, keeping VDD as clean as possible.

2. If you are not using the shield pins they can be left floating.

Best Regards,

0 Richard Wu2 over 6 years ago in reply to Kristin Jones93

Prodigy 20 points

Hi Kristin, thanks for the help. I do have another question for you.

I have connected 1 conducting strip (sensor) to the CIN1 channel of an FDC1004, but have not put another conducting strip for my sensors ground. I then supply the VIN with 3.3 V, and connect the GND.

My question is...

How does the FDC1004 actually read the capacitance of the conducting strip (sensor)?

Thanks,

Richard

0 Kristin Jones93 over 6 years ago in reply to Richard Wu2

TI__Genius 17440 points

Hi Richard,

The FDC1004 used a switched-capacitor circuit, which you can read more about here.

Best Regards,

Sensors

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FDC1004: Added capacitors to VDD, and to SHIELD