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INA231EVM: Powers Down after Reading All Regs

Matthew Rodeman
Prodigy 730 points
Part Number: INA231EVM

Hi,

I'm trying to use the INA to measure output current across a shunt resistor in a current sink for the amplifier independent study in my rotation. I'm pretty sure the hardware for the EVM is configured correctly after reading the user guide, but I'm getting issues with the software (I believe).

I have A0 and A1 set to GND. I'm trying to operate in Shunt and Bus, Continuous mode with an Averaging Mode of 1. My bus and shunt conversion times are both set to 140 us. I'm configuring based on the Current LSB. I input a resistance of 1.7 ohm and max current of 2 A (should only get to about 1.5 A, so this can be changed) for a current LSB of 100 uA. I'm not configuring any alerts. However, when I hit Read All Regs after pressing Write All Regs, no voltage is read across the shunt resistor (or current) and the operating mode changes to Power Down. I know from measuring the shunt resistor with a multimeter that there's a voltage across it, but that's not being read by the INA. What might be the problem?

  • 0
    TI__Mastermind 32395 points

    Hey Matthew,

    I am looking this over and will respond shortly.

    Peter

  • 0
    TI__Mastermind 32395 points

    Hey Matthew,

    Would you please send a schematic or picture of your setup and screenshots of the GUI before and after writing and reading the registers?

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    TI__Prodigy 730 points

    This is the physical setup of the circuit. Note that the VIN- and GND pins on the EVM are shorted. Below is the schematic of my circuit:

    The VIN+ pin is connected to the same node as the source of the NFET and the inverting input of the op-amp.

    Here's a video of what I was seeing with the EVM software.

  • 0 in reply to Matthew Rodeman
    TI__Mastermind 32395 points

    Hey Matthew,

    Is the 5V source for the device as the 5V source for FET and load?

    Can you please repeat the video, but with the registers tab opened, I don't see anything indicating that the device is going into power down?

    What is the approximate current going through FET during the test via measuring the voltage drop across the shunt resistor or by looking at source current readout from the 5V source instrument?

    Sincerely,

    Peter