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INA219: INA219 - Bidirectional current measurement to measure motor current?

Smitha R
Intellectual 790 points
Part Number: INA219
Other Parts Discussed in Thread: INA253, INA240

Hi,

we would like to use INA219 to measure motor current in our application. 

We would like to confirm on whether INA219 can be used to measure motor current in H-Bridge motor control  i.e by placing shunt resistor in the middle of the H-bridge to accurately measure current in both directions.  

Datasheet says to connect positive side of shunt to IN+ pin and negative side of shunt to IN- pin.  But in our application IN+ and IN- can become negative side and positive side of shunt respectively if motor current changes direction.  so please confirm if we can use INA219 though datasheet says it can measure bidirectional.

Awaiting for the quick response!

Thanks,

Smitha R

  • 0
    TI__Mastermind 27715 points

    Hello Smitha,

    The INA219 can indeed be used for bidirectional current sensing. However, the common-mode voltage (Vcm) at the INA219 inputs must stay within the maximum limits of -0.3V to 26V. In your H-bridge motor control application, what does the load voltage look like when current changes direction?

    Best regards,

    Ian Williams
    Applications Manager
    Current & Magnetic Sensing

  • 0 in reply to Ian Williams
    Intellectual 790 points

    Hello Ian,

    Thank you for the reply. We shall take care of the common mode voltage as our motors are powered from 12V rails.  Please find the attached circuit where we intend to introduce this device. Please let us know if any other thing needs to be taken care of.

  • 0 in reply to Smitha R
    TI__Mastermind 35180 points

    Hi Smitha,

    The INA219 most likely can’t be used as you indicated for a couple of reasons.

    The first reason is input common mode voltage – the bus voltage of 12V is within the specified common mode range, however the current sense amplifier also needs to withstand a negative common mode voltage of at least -1.5V. Clearly INA219 is not be able to do that.

    The second reason is more subtle and it has to do with PWM rejection. The amplifier must be able to withstand the PWM edges, not latch up and destroy itself. Further it needs to reject the PWM disturbances in order not to corrupt the output.

    We have several analog output current sense amplifiers that can be used here, but by far the best candidate is INA240. Unfortunately we don’t have an equivalent digital output version at this moment; therefore you’ll need an ADC channel from the controller. INA253 is basically INA240 plus an internal integrated shunt of ~2mOhm. It might be a good option too.

    Regards, Guang