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ISO 122 Problem

Hartog Roos
Prodigy 20 points
Other Parts Discussed in Thread: ISO122

We are using an ISO 122 Isolation amplifier, with independent +/- 5 Volt power supplies as per the recomendations on thedata sheet. The amplifier is intended to be used with a DC input between 0 and 4 Volts. The problem we are having is that the output signal only follows the input accurately up to an output up to 2.94 Volts, even if the input voltage continues to increase up to 4 Volts.

Although we could not find an answer in the data sheet, Is this normal when using +/- 5 Volt supplies?

  • 0
    TI__Guru* 93105 points

    Hello Hartog,

    The ISO122 input and output ranges for these sections are not specified with a +/-5 V supplies as it is for +/-15 V supplies. You will note that with the +/-15 V supplies the input and output sections have a minimum specified swing of +/-10 V, five volts from each supply rail; and a typical swing of +/-12.5 V, two and a half volts from each supply rail.

    The swing ranges relative to the supply voltage levels doesn't change much. Therefore, with the supplies set to +/-5 V, the input and output section swing voltages are typically 2.5 V from each rail; so typically the swing is limited to about +/-2.5 V. The fact that it is swinging to 2.94 V with a +/-5 V supply is very reasonable. The only possible way to increase the swing range is to increase the supply voltage level.

    Regards, Thomas

    PA - Linear Applications Engineering

  • 0 in reply to Thomas Kuehl
    Prodigy 20 points

    Thanks Thomas,

    With our applicatuion we can cope with +2.5 V swing, just wondered since we couldn't evidence in the product data sheet.

    Regards,

    Hartog