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INA2180: Unused CSMs: floating or GNDed?

Part Number: INA2180

Hi Team,

For current shunt monitors like the INA2180, if one of the channels were not used for some reason, should the unused amp be left floating, GND'ed, or shoudl it be configured differently?

  • Hi David,

    connecting both inputs of the unused channel with shortest connections to the ground pin of INA2180 is a good idea. Let the associated output pin float, though.

    Kai

  • Hello David,

    I agree with Kai.  If you need them to be available place some shorting resistors to GND and a node you can connect to another node at a future time.  Then all you need to do is remove shorting resistors.

  • Hi Kai and Javier,

    Thanks, appreciate it. Somewhat related question, in the case when the INA2180 is not supplied power, but IN+ and IN- are around 10V, the output of the current sense amp would still be limited by Vs at 0V, correct? Or will the output gradually rise to ~10V?

  • Hello David,

    With the power not available the output does get biased through the inputs.  The output does go to about 0.6V even when the input 10V VCM and inputs shorted.  As soon as the Vs goes to an operating point it returns to the correct output.

    When VS = 0V the output is not enabled so the drive is very limited as it is not a normal operation.  With a 10kΩ load to GND we were able to drop it down to 0.2V.  I assume as you increase the load you can drop the voltage even further.