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INA226: Reverse current measurement in low side shunt configuration

Part Number: INA226
Other Parts Discussed in Thread: AMC1203, AMC1200

Hello,

Low side shunt configuration, one side of shunt resister is connected to GND which will be the same node of INA226 GND.

When reverse current measurement, the common voltage of shunt resister would become lower than GND.

Typical ADC, ADC measurement range is VREF to GND. the above condition would be out of ADC range.

I am wondering why INA226 can measure the differential voltage between +/-81.92mV?

To see the datasheet. V measurement is referred as GND and I measurement is referred as IN-. From this description, i guess it can be measured because it is differential voltage measurement. But still I couldn't understand why ADC can measure the voltage below GND.

Is INA226 has an architecture negative common voltage can be measured accurately? AMC1200 or AMC1203 can also measure negative differential voltage.

I think these devices also be the same.

Would you explain why negative voltage measurement can be done for better understanding?

Best regards,

Toshihiro Watanabe

  • Hi Toshihiro Watanabe-san,

    The differential input signal is level shifted up by the input stage, such that the resultant signal is within the measurement range of the integrated ADC. This is the trick that enables negative input voltage measurement.

    The bidirectional situation as you described should be no problem to handle by INA226.

    Regards, Guang