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INA190: How to achieve bi-directional current measurement

Miles Li1
Intellectual 1640 points
Part Number: INA190

Team,

Customer is asking how INA190 measure bi-directional flowing current if VREF is connected to GND? Could it work? As it says in the datasheet, if it need to measure bi-directional current, VREF should be connected to positive voltage.

Wish to get your reply, thanks!

  • 0
    TI__Mastermind 19235 points

    Miles,

    Typically, for our devices, what this paragraph explains is that Vref would be set to mid-supply, and then half of the range would measure from mid-supply to GND, and the other direction would measure mid-supply to Vs. 

    To perform bidirectional sensing with Vref = 0V, the customer would need to reference the device to a voltage below GND at the GND pin. For example, you could make Vs = 2.5V, and GND = -2.5V, with a reference of 0V to operate at the midpoint of these voltages.

    Keep in mind that recommended operating specifications and absolute maximums are dictated with respect to a reference of 0V in the datasheet, so these need to be adjusted and kept in check as well. For example, Vs absolute maximum is 6V, so with GND referenced to -2.5V, the Vs pin would need to be kept under 3.5V to satisfy this condition (3.5V - (-2.5V) = 6V).

    Let me know if you have any additional questions. 

  • 0 in reply to Carolus Andrews
    TI__Intellectual 1640 points

    Hi，

    Thanks for the reply. So, you mean, if I tied Vref to GND, and measure -0.5V to 0.5V, the output of INA190 could be -V to +V, reference to GND，

    right?

  • 0 in reply to Miles Li1
    TI__Mastermind 19235 points

    Miles,

    When I say "reference" here, I am referring to the voltage placed at the GND pin. Normally, the reference voltage is 0V, so Vs is simply Vs (Vs - 0V = Vs). This changes because you have placed a voltage on the GND pin that must now be taken into the difference Vs - reference at GND). 

    If you place Vref at 0V, and place 2.5V and -2.5V on Vs and GND respectively, the output of the device when VSENSE = 0V would be 0V. Then, the Rshunt*I_Load*GAIN would work as usual in either direction up to the swing to rail/GND limits much like a typical operational amplifier.