Is there a single chip ADC designed for reading a capacitor bridge circuit?

[ballen]

The HX711 is a "load cell amplifier".  This is chip containing a differential 24-bit ADC, clock, and voltage regulators, for reading a resistive bridge circuit.  They are used to read the load cell (strain gauge bridge) in inexpensive digital scales.  Typical full-scale sensitivity is ~20mV, meaning that the single bit resolution is around 1nV.

Is there a similar chip, intended to read out a capacitor bridge circuit?

[Kleinstein]

There are ADCs to read capacitors, though I don't remember the method they use. It may be a little different from a bridge.
AFAIK Analog has some.  Even some µCs (PIC) include HW for capacitance reading.

[Terry Bites]

The FDC1004 from TI may well work for you. Also see AD5941.

[ballen]

FDC1004 looks good, thank you!  Another one I just found is the AD7745.

[David Hess]

The HX711 is a "load cell amplifier".  This is chip containing a differential 24-bit ADC, clock, and voltage regulators, for reading a resistive bridge circuit.  They are used to read the load cell (strain gauge bridge) in inexpensive digital scales.  Typical full-scale sensitivity is ~20mV, meaning that the single bit resolution is around 1nV.

Single bit resolution (quantitation noise) has nothing to do with true resolution when the input noise is 250 to 500 times greater.  Lop off the 8 or 9 least significant bits.

With 10 volts of excitation, that could deliver 80,000 counts but the typical application circuit only has an excitation of 2.5 volts limiting the resolution to 20,000 counts or 14.3 bits, which may seems low but is consistent with the accuracy of an excellent strain gauge load cell.

[T3sl4co1l]

FYI, I designed a nice bridge circuit (it's not a one-chip solution) specifically for small capacitances at a low frequency; I could ask the client to see if they're interested in sharing/licensing it.  (Probably a long shot, but eh.)

Tim

[Terry Bites]

Yes the AD7745/AD7746 look like the very thing you want. I wasnt aware of them, thanks.

[David Hess]

Also take a look at how the signal conditioning of relative humidity sensors works.  They are capacitive with a range of about 350 to 550 picofarads but the concept works over any range.

[spostma]

some microcontrollers have ADCs with capacitive voltage divider stages.
Microchip calls this CVD ADC, intended for capacitive touch sensors.

[babysitter]

Have a look at this:

https://www.pmt-fl.com/picocap/picocap-capacitance-measurement

Example datasheet (aged?) here: https://www.sciosense.com/wp-content/uploads/documents/Datasheet-PCAP02-Volume-1.pdf

BR
Hendrik