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ISO121: Applying INPUT signal to the output of ISO121 IC

Sivakumar Shanmugam
Prodigy 30 points
Part Number: ISO121
Other Parts Discussed in Thread: ISO224

Hi,

We are using ISO121BG for one of our Isolation requirement.

Per the design requirement, we are in need to apply 10V DC input to the VOUT (pin 18) of IC ISO121BG continuously while there is an input signal of 5V DC still in the VIN (Pin 39).

Will there be any damage to the IC during this condition?

  • 0
    TI__Guru**** 176181 points
    Hi Sivakumar,

    Why do you need to apply 10V to the output of the ISO121? This device only has a gain of 1, so with 5V on the input, it would normally be 5V on the output. What are the +/- VS1 and +/-VS2 rails during this condition?
  • 0 in reply to Tom Hendrick
    Prodigy 30 points

    During testing of one SHORT function, the 10 V will be applied to the output of the iso amp.  Need to know the impact of this with ic and what will happen at the input?

    The supply rails are separate +/- 9 VDC for input and output.

  • 0 in reply to Sivakumar Shanmugam
    TI__Guru**** 176181 points

    Hi Siva,

    So long as the 10V source current is limited to 10mA or less, you should be OK. The input should not be impacted.  However, if this is a new design, you might want to consider taking a look at the ISO224 as an alternative device.