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INA233: Dissatisfied reading

Annie Liu
Genius 10295 points
Part Number: INA233

Hi Team,

The customer sets the current value of INA233 to an overcurrent state. He uses a multimeter to test that the voltage across Rshunt was 118mV, which was greater than the maximum measurement range. But the printed code is 31999 (0x7CFF), not 32768 (0x7FFF). Would you possible to check the reason?

  • 0
    TI__Genius 10295 points

    感谢您对TI产品的关注！为更加有效地解决您的问题，我需要询问更了解这款芯片的TI资深工程师，再为您解答，一旦得到回复会立即回复给您。

  • 0 in reply to Annie Liu
    TI__Mastermind 34310 points

    Hi Annie,

    Register 89h returns calculated current as explained in this paragraph:

    The value is scaled based on the calibration register. Therefore an out-of-range Vshunt does not necessarily produce an out-of-range current.

    For a valid verification, please read register D1h, which is a direct reflection of the Vshunt and customer should see its value overflows.

    Regards, Guang

  • 0 in reply to Guang Zhou
    TI__Genius 10295 points

    Hi Guang,

    He read it with Vshunt, it is accurate. 

    And he has further questions and needs help. Is he able to change the value of the calibration register, and then the maximum value of READ_IIN will change accordingly? He uses INA233 for over-current protection. When the current value exceeds 100mA, Alert will respond. After he passes the calculation, the selected threshold is 0x7DFF. However, in this case, it can only count up to 0x7CFF, and protect it before reaching the set overcurrent point. Customer would like to know how to resolve it?

    Thanks,

    Annie

  • 0 in reply to Annie Liu
    TI__Mastermind 34310 points

    Hi Annie,

    This video talks about how to program power monitors, with INA233 being used as an example. On slide #6 the equations under “FYI only - How internal register values are calculated by power monitors” can be used to address your customer’s question. If you find yourself spending too much time on it, please provide a couple pieces of  information and I'll be more than happy to make the calculation for you:

    (1)   Shunt resistor value

    (2)   Calibration register value

    Regards, Guang