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INA303: Upper limit exceeds typical Hysteresis

Akhil Rajendran
Prodigy 10 points
Part Number: INA303

We used VREF = 0, VS = 3.3 V, VIN+ = 24 V, ILIMIT1 = 600mA, and ILIMIT2 = 90mA, as our design constraints. Hence we provided RLIMIT1=3K and RLIMIT2= 470R.During our testing, the hysteresis of comparator 2 is observed to be around 110mA in our case(VLIMIT2/80uA). But the hysteresis of comparator 1 differs in large amount of about 260mA(VLIMIT1/80uA) from the typical hysterisis value(100mV Typ.) claimed in the datasheet.For better under standing, A graphical representation of test values are attached.

  • 0
    TI__Mastermind 30320 points

    Hi,

    What is the shunt resistor being used? I deduced its value using given information, but got different values based on the two comparator results. 

    How repeatable is the set of test results? Is it possible to capture above waveforms with an oscilloscope and post here?

    Regards, Guang  

  • 0 in reply to Guang Zhou
    Prodigy 10 points

    Hi,

    Sorry for the late reply. For more clarification we made one more test case and in that, we used a function generator to give the input to the chip. We removed the shunt and fed the DC signal from the generator in that place. RLIMIT1 was 3k and RLIMIT2 was 300R. The hysteresis graph drawn by varying the DC input.

    In this graph, the hysterisis of the first comparator is different as described in the datasheet. This the issue tested on multiple chips and found to have the same behavioural pattern.

  • 0 in reply to Akhil Rajendran
    TI__Mastermind 30320 points

    Hi,

    The limit of 24mV is below the output swing of the amplifier. Together with other error sources, it will cause the hysteresis to appear to be off. But it still doesn’t account for the large amount.

    As an experiment, can you make RLIMIT2 3k or larger to see it make any difference?

    Regards, Guang  

  • 0 in reply to Guang Zhou
    Prodigy 10 points

    The Differential input voltage range of the chip is 0 to ±125 in the datasheet and we are operating in that range. I didnt get more information about the amplifier swing from the datasheet. Can you please specify the range of output swing of the amplifier? 

  • +1 in reply to Akhil Rajendran
    TI__Mastermind 30320 points

    Hi,

    The output swing to ground is specified as:

    Did you have a chance to see if it makes any difference by setting RLIMIT2 3k or larger? It is just an experiment to help understand the issue.

    Regards, Guang  

  • 0 in reply to Guang Zhou
    Prodigy 10 points

    Hi,

    We changed RLIMIT2 to 3K and noted the hysterisis. It's matching with the typical hysterisis values. Thank you for your support.