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INA901-SP: Absolute Maximum Input Current Into Pins

Dan Oliver
Prodigy 60 points
Part Number: INA901-SP

I am trying to prepare for a series of RAD tests on this component.  I have a basic circuit on a PCB built to allow the device to run at very simple, static voltages & currents based on MIL-STD883 .  I have pins 3 & 4 shorted together and floating because I do not believe I need them to get this to run for my tests.  I am not sure if that point will matter.

The datasheet says the Absolute Maximum Input Current into any pin is 5mA.  Does this mean that I need to limit my Supply voltage to less than 5mA?  I have my power supply set to 4mA output at 7V.  I am supplying a voltage to the Common Mode voltage input, but neither the Supply nor the Common Mode voltages are coming up to the voltages I have set on the power supply.  My Supply voltage is only going to approximately 0.43V and putting out about 4.3mA.  At the same time, my Common Mode voltage is only going to 1/5th the voltage I have set but is putting out the maximum current I set.  It should be noted that I have an electronic load being used in Constant Current mode set to match the power supply's output current, so I believe that is why my CM current is correct, but why would the voltage not climb to the output setpoint of over 10V?  Is my device not actually turning on because my Supply voltage is < 2.7V?

I disconnected the device from my PCB and then turned on my power supplies.  I had to turn the output current for the Supply Voltage up to 70mA before I had 7V available from the supply.  I am afraid if I turn up the current to 70mA to get the 7V I need, I will damage or destroy the INA901-SP.

Any guidance will be greatly appreciated.

  • 0
    Prodigy 60 points

    A further question.  I see that there is a note that the max supply current draw is 1200 μA.  So is the 5 mA max current into any pins something I only need to worry about on the other pins since the supply (V+) will not pull any more than that?

    § 6.1 Input current into any pin = 5 mA

    § 7.1 The INA901-SP operates from a single 2.7-V to 18-V supply, drawing a maximum of 1200 μA of supply current.

  • 0
    TI__Intellectual 1990 points

    Hi Dan, 

    To clarify, you are saying when the INA901-SP is removed from the board it take 70mA to achieve 7V? Or when the electronic load is removed from the common mode?

    Do you have a large resistive load on the output of the INA901-SP? If this is the case you would need to supply additional current to the device. While the quiescent current of the device is 1.2mA max, if you have a large resistive load on the output, the device will draw more current to buffer the load. Quiescent current is used to power the IC, buffering the load requires additional current. The device acts linear up to ~10mA of current when there is about 7V on supply - see figure 7 in the datasheet.  Therefore, in a scenario where the load is drawing 10mA, the overall device could draw up to 11.2mA of current.

    If there is a load on Vout, it would be good to reduce it or remove it temporarily to see if the device operates as expected. 

    -Kyle