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INA169: Current sensing

Part Number: INA169


Hi Expert,

Good day!

This is about the current regulator circuit. I wanted to use the current sensing IC INA169. I want to be able to sense current from 0-1A. The image below shows the schematic and simulation graph. Using the Spice model available. Here is the result.

The red line in the graph is sensing current. The green line is the voltage on the output (Pin 1). On the X axis is voltage from voltage source V1. My question is if the spike on the output at voltage V1 = (cca) 3,2V is Spice model error or if it is correct. Differential input voltage V-shunt is around 50mV at the spike.

If it is not a spice error, would you recommend another current sensing IC that is sufficient for this application The voltage supply for this application is 30V and the output current is 0 to 1A.

Thank you in advance for your support.

Best regards,


  • Hey Jonathan,

    I think this is due to a combination of the 2.7V minimum common mode voltage (Vcm) and the minimum Vout compliance voltage (Vout-0.5V), see below from datasheet:

    Essentially, the model is showing inaccurate behavior for Vcm < 2.7, although it is not exactly accurate as the spike happens at 3.2V Vcm. However, at the same time device is trying to model Vout compliance which for this case will be a maximum level of Vout-0.5V. At the Vcm=3.2V, the Vout_compliance is 2.7V. In the plot, Vout drops from 3V to 2V right when Vcm is at 3.2V. Any simulation model should not be considered as the true device behavior. In this case, you can rely upon the INA169 datasheet specifications and behavior to determine if this circuit will work for you system.

    If the simulation is showing exactly the load and bus voltage you want to monitor and you need accurate measurements for Vcm <2.7V, then you definitely need to consider another device. If you do not need operation at <2.7V, but the INA169's Vout_compliance may exceed VIN- at some point, then you will either need to increase shunt voltage gain (increase R1 or R3) or choose another device.

    If you need a current sense amplifier (CSA) that has adjustable gain, you can consider using this circuit which converts any bidirectional voltage-output CSA into a current output circuit, similar to the INA169: