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INA300: Asking for the INA300’s OCP trip point

Part Number: INA300

Hi Team,

Customer is using INA300 solution. Would you please help check what the OCP for this circuit?

Schematic link

txn.box.com/.../yry27629j2dzef9zsttctylvk762404c

 

 Rlimit= 1.96kohm

Rsense=0.005ohm

BR,

SHH

 

  • Hi Shh,

    this is very well explained in section 7.3.2 of datasheet.

    Kai

  • Hi Kai,

    customer changed Rsense as below and doing the load test.

    VTRIP= VLimt =Rlimit X 20uA-500uV

                               =1.96x0.020-0.0005

                               =0.0387

    RSense  change to 0.01 ohm 

    I Load = VTRIP/ Rsense =0.0387/0.01=3.87A.

    however, the INA300 alert pin is still high even the e-load is running up to 4.52A.

    Would you please provide some comment for this alert not response case?

    thanks for help.

    BR,

    SHH

  • Hey SHH,

    There definitely seems to be something wrong here. The calculations for the OCP are correct and the schematic looks ok so there could be something wrong with the hardware. I would recommend these debug steps:

    1. Ensure that the electronic load is not off in its calibration. Try measuring the shunt voltage drop directly at the input pins (IN+ and IN-) of the INA300. If the sensing traces are not in proper Kelvin sense connections, then the INA300 could be sensing a voltage drop across a resistance that is not 10mOhm. Providing a simple layout picture can help us verify this is not the case.

    Also measuring the voltage across the shunt resistor from the top pads of the resistor can potentially show a difference between the shunt voltage and the sense voltage of the INA300.

    2. At what current does the INA300 trip at if at all?

    3. Remove the FET and from the ALERT pin and repeat the test. Maybe this circuitry is interacting with the ALERT pin's ability to pull-low.

    Sincerely,

    Peter

  • Hi SHH,

    It's been a week since your last post, so hopefully your issue has been resolved. Please give an update with responses to Peter's questions if you need more assistance.

    Best regards,

    Ian Williams
    Applications Manager
    Current Sensing