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INA190: Voltage across Vin- pin when IC is disabled

Lucas Claudino
Prodigy 20 points
Part Number: INA190

Hi folks

I have designed a circuit to measure low currents such as 15uA using INA190. However, I am having an issue when I tray to disable the IC. I will try to explain.

Initially, the circuit is as following:

When I apply 3V3 to Csense, I can measure the current across R14.

The problem is when I try to disable U4. If I pull Cs_EN to zero, apply 3V3 to Csense, I am getting 2.8V at IN- pin.

I even tried to remove R14, and the voltage at IN- still at 2.8V.

I also tried other drastic test: I removed R12, R13 and C8, disabled U4 pulling pin 2 to low, and still measuring 2.8V at pin 8.

The IC is not damaged, because the same behaviour happens when I change IC or try another PCB.

Does someone have a clue on this?

Thank you

  • 0
    Guru 140200 points

    Hi Lucas,

    what else is connected to pin 8 when you disable the INA190? And what is connected to pin 8 under normal operation, with the INA190 enabled?

    Kai

  • 0 in reply to kai klaas69
    Prodigy 20 points

    Hi Kai,

    Initially, it was connected an electronic circuit (mainly a IC and a few passives).
    Later, when I started noticing this issue, I removed all this circuit and put a 100kOhm load, to simulate the real load. For both cases, I am having the same behabiour: 2.8V at IN- when the INA190 is theoretically disabled via EN pin.

    Cheers

  • 0 in reply to Lucas Claudino
    TI__Mastermind 18780 points

    Lucas,

    A few more questions here:

    - When you ran the last test (100kΩ), was the 330Ω shunt also installed? I am trying to understand how the input is configured for this test, as there must be a proper pathway for input bias currents to flow at all times with our devices.

    - When you disable the INA190, what happens to Csense? Are you also removing this voltage from the load? I want to understand if you are shutting down everything around the part, or if the load is continuing to be operated, and the part is simply being disabled.

    - Is the enable pin properly shutting off the output as intended?