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FDC2112: How to calculate the sensor-activation time, conversion time, and channel-switch delay?

Part Number: FDC2112

Hi TEAM,

From the datasheet of FDC2112, on Page 17, how to get the vale of 1.8ms,3.2ms,0.75ms?

Thanks a lot

Matthew Chen

  • Hello Mathew, 

    • The sensor activation time can be calculated using equation 3 in the datasheet: 
    • You can calculate the conversion time by using equation 5 in the datasheet: 
    • The switch delay can be determined by using equation 6 in the datasheet: 

    Fref is the clock frequency after the dividers

    It seems like when they put these calculations in the datasheet, a consistent Fref was not used and the numbers were not double checked. If you use a 10Mhz Fref and the same register settings from the datasheet, you get the following: 

    0.2ms (sensor-activation time) + 0.82ms (conversion time) + 0.001ms (channel-switch delay) = 1.21ms per channel 

    Best Regards, 

    Justin Beigel

  • Hi Justin,

    thanks for your kindly reply.

    What's the value of CHx_SETTLECOUNT, CHx_RCOUNT and fREFx when you calculate? I know how to calculate the delay time.

    Could you tell me where is the '' register settings'' you mentioned in the datasheet? 

    Matthew

  • Hello Mathew,

    In the paragraph you quoted from the datasheet, it mentions an RCOUNT of 512 and a SETTLECOUNT of 128. 

    I then chose to use 10MHz for the Fref in my calculations. This is just an example number and doesn't correlate to an actual application. 

    Best Regards, 

    Justin Beigel