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UCC2819

Ram Sivanehru
Prodigy 90 points
Other Parts Discussed in Thread: UCC2818

Hi,

The output pin VFF(pin 8) could be used for measuring the input mains; but the datasheet forUCC2819 is not very clear, so I am referring UCC2818 datasheet.

Voltage could be generated at Vff if we use a resistor;  the calculations for the resistor in page 10 has a constant (0.9).

does anyone know the reason for this constant in the equation.

Thank you

Siva

  • 0
    TI__Genius 9130 points

    Ram,

     

     

    Apologies for the delay with this response.

     

     

    The RC filter on the VFF pin will produce a voltage that is proportional to the average of the AC input voltage, rather than the RMS value.

     

     

    The ratio of the average value of a half sine to the RMS value is 0.9, that is where the factor comes from.

     

     

    The 0.9 value is actually = 2 * SQRT(2)/ Pi = (2 * 1.4142) / 3.13159 = 0.9003.

     

     

    I hope this answers your question.

     

     

    Thanks,

    Bernard