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FDC2112: Capacitance-to-digital converter

Nikhil Jadhav
Prodigy 50 points
Part Number: FDC2112
Other Parts Discussed in Thread: DAC7571,

Hi,

I want to design a system for capacitance-to-analog converter. For this, i am not able to find any TI IC that can directly convert capacitance-to-analog voltage/PWM.

So, I am planning to use capacitance-to-digital converter IC part# FDC2112QDNTRQ1 (Digital output over I2C) followed by I2C based DAC part# DAC7571IDBVT.

Here, query is:

Can i connect both of this parts back to back for complete capacitance-to-analog converter? How DAC can directly communicate with I2C output of cap-to-digital converter? Is there anything i should take care of here?

Please help to resolve above queries/doubts here.

Regards,

Nikhil Jadhav

  • +1
    TI__Mastermind 18545 points

    Hello Nikhil, 

    In order for the two devices to be connected back to back, one of them would have to be the master on the I2C bus. Neither the FDC2112 or DAC7571 have this capability so you will need an MCU to move the capacitance information to the DAC. You will need an MCU already to initialize the FDC2112 so it is just a matter of having the extra step through the MCU in data communication to get your analog output. 

    Best Regards, 

    Justin Beigel

  • 0
    Prodigy 50 points

    Hi

    Thanks for the quick response on query. 

    Just couple of more queries below:

    1) Is there any other TI sensor available which has master I2C capability?

    2) Is there any other TI sensor available which can convert capacitance-to-analog directly?

    P.S. Our requirement is:

    Input: 10pF to 300pF capacitance

    Analog Output: 1V to 3V

    Ultimately, we want to detect change in capacitance.

    Regards,

    Nikhil Jadhav

  • +1 in reply to Nikhil Jadhav
    TI__Mastermind 18545 points

    Hello Nikhil, 

    1. You would need an MCU to be the I2C master. Some MCUs have special functionality on some of their pins like our CapTIvate line of MSPs which are designed for capacitive touch. But none of our dedicated sensors have the ability to be a master on the I2C bus. 
    2. Unfortunately, none of our capacitance sensors offer the capacitance-to-analog option. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    Prodigy 50 points

    Hi,

    Just wanted to confirm: Can i measure capacitance between 10pF to 300pF using FDC2112 ?

    Regards,

    Nikhil Jadhav

  • 0 in reply to Nikhil Jadhav
    TI__Mastermind 18545 points

    Hello Nikhil, 

    Yes, the max capacitance measurable with this device is 250nF. 

    Best Regards, 

    Justin Beigel