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PCM4220: PCM4220

Steven Wen
Prodigy 90 points
Part Number: PCM4220

 Do you have this information or a methodological characterization of the input impedance? the d/s said 2.8K ohm.

  • 0
    TI__Guru 62085 points

    Hello Steven,

    The input impedance is directly a function of the internal S&H circuitry timing and capacitance.  The timing will be tight, but the absolute value of the input capacitance will vary from normal manufacturing variances.  The 2.8k value will be the typical value with roughly +/- 20% as the approximate +/-3-sigma value.  Therefore sigma would theoretically be about +/-7% over devices.

  • 0 in reply to Collin Wells
    Prodigy 90 points

    Hi  Collin,

    How does the input impedance change vs temperature? especially in CT? 

  • 0 in reply to Steven Wen
    TI__Guru 62085 points

    Hello,

    Took a little longer to dig into this one.  While the absolute value will vary based on the range stated previously, the temperature drift of these components is fairly low in the 10-20ppm/C range.  Since the input impedance on this type of modulator is directly related to the sampling cap and sampling frequency, drift on the provided external clock source will also impact the input impedance.