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VFC32: Frequency Capabilities

Nicholas Nelson
Prodigy 10 points
Part Number: VFC32

I am looking into using the VFC32KP IC to convert a frequency to an analog voltage signal, and I was wondering if this chip will be capable of converting frequencies that range from 0-50 Hz. By looking at the data sheet, I will need a C1 value of 3.3uF and C2 value of 100uF along with a R1 value of 40K to make this chip read frequencies in this range.

  • 0
    TI__Guru* 93105 points

    Hello Nicholas,

    The VFC32 should be usable and scalable as an F-to-V converter for a frequency range of 0 to 50 Hz. When I calculate the value of C1 using the equation in the Specifications table, I find that it should be 667 nF.

    VOUT = 7.5 R1 C1 FIN

    If R1 = 10 k, VOUT = 10 V and FIN = 50 Hz,

    Then, C1 = VOUT / (7.5 R1 FIN) = 10 V / [(7.5) (4e4) (5e1)] = 667e-9 = 667 nF

    Extrapolating the C2 line in datasheet Fig. 2 down to 50 Hz it appears that it should be about 6.7 uF.

    The capacitors will need to be high quality for accurate results. C1 can be a film capacitor, but C2 will be a more difficult to realize. It shouldn't be an electrolytic capacitor because they are have wide tolerances and are less than ideal. This may need to be a large film capacitor.

    Regards, Thomas

    Precision Amplifiers Applications Engineering