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INA186: Possibility of reverse current

FRANK1
Expert 7835 points
Part Number: INA186

Hi sir,

I wanna select TI INA186 in my circuit.
In theory, the current will only flow in one direction.
If the REF pin is connected to GND.
Is there any possibility that a slightly reverse current may occur for the current measurement side?
In this case, does the output voltage of the OUT pin become 0V (= REF pin voltage)?
Is there any possibility that the IC will be damaged?
Thanks.
Regards,

  • 0
    Guru 243120 points

    When the two inputs are equal, the input offset voltage might cause a slightly negative output.

    However, the amplifier cannot drive the output to a voltage outside of the supply rails. When REF = GND, the output will stay at GND, or slightly above GND if the output needs to sink some current. The is specified as VZL in the datasheet.

  • 0
    TI__Mastermind 26660 points

    Hey FRANK1,

    The INA186 is meant to operate normally and maintain accuracy/CMRR with input common-mode voltages from -0.1V to 40V according to the CMR spec in datasheet. So there is no possibility of damage. In fact, the survivable VCM range is -0.3V to 42V. This is all true regardless of the voltage at REF pin.

    Additionally, the input bias current for the INA186 is only positive for VCM from 0V to 40V according to Figure 6.

    Finally, as Clemens mentioned, if REF = GND and Vsense <= 0mV, then the output voltage of INA186 (Vout) will be saturated and slamming into GND. While this means you cannot get accurate data, the device will not break. In fact, Vsense can go all the way to -42V differential according to the Absolute Maximum Rating Table and the device will be perfectly fine. When Vout is slamming into ground, it cannot reach a perfect 0V, instead it will hit a voltage floor where Vout = VZL from datasheet, which is around a few milli-Volts.

    Hope this helps.

    Best,

    Peter