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Current Sense Amplifier for high voltage motor phase currents

Other Parts Discussed in Thread: INA819, INA149, AMC1200, AMC1100, INA148


I am looking for a current sense amplifier for the phase current sensing application for a PMSM motor. I have shunt in motor phase, my DC link voltage can be 400V. I could not find high common mode voltage amplifier.  I want to use non-isolated solution. Is that possible?


  • Hello Chaitanyab,

    Our non-isolated amplifiers top out at +/-275 V with the INA149 difference amplifier. It is very difficult without using internal isolation methods to support voltages any higher. You might be able to set up a resistive high voltage dividers off the shunt followed by a 3-amplifier instrumentation amplifier such as INA819. The resistive divider will reduce the sense voltage by the divider ratio, but you can gain up that smaller voltage with the instrumentation amplifier.

    TI does have low cost isolated amplifiers that use capacitive isolation rather than transformer isolation and are available in the SOIC(8) package. Ones that I am most familiar with are the AMC1100 and AMC1200. Have a look at one of their datasheets, it may be they would do what you need:

    Please note that the AMC amplifier products are from a different amplifier product group than those we support here on the Precision Amplifiers e2e forum. When I search AMC1200 it comes up under Amplifiers > Amplifiers Forum. Someone from TI supporting that forum should be able to assist you if you think one of the isolated amplifiers can do what you need.

    Regards, Thomas

    Precision Amplifiers 

  • Adding to Tom's comments, you do not specify supply voltage you use to power your amplifier.  If you use a single supply 0 to 30V, INA149 and INA148 will meet your requirements; the linear input common-mode voltage range of INA149 is from 0 to 550V while 0V<Vcm<400V for INA148 for 30V single supply application.