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INA302-Q1: Using Alert for Bidirectional Overcurrent Thresholds

Rohan Patwardhan1
Intellectual 340 points
Part Number: INA302-Q1
Other Parts Discussed in Thread: INA302, INA303

Hi Team,

I am planning to use INA302 for current sensing and overcurrent protection. Since INA302 is a bidirectional device where the reference pin can be offset with a particular voltage, it must be possible to set overcurrent protection for charging and discharging current. However the datasheet explicitly mentions INA303 only. Can INA302 achieve the same functionality?

Thanks,
Rohan 

  • 0
    TI__Mastermind 21720 points

    Hello Rohan,

    Thanks for considering to use Texas Instruments.  The INA302 and INA303 have the same specs and are able to sense in either direction.  However, their key difference is how their ALERT functions.  Based upon figures 45 and 46 in the datasheet, it appears as though this may only be available for one direction.  I will see if I can confirm this on the bench on Monday.

  • 0 in reply to Patrick Simmons
    Intellectual 340 points

    Hi Patrick,

    Thank you for the response. Please let me know when you have an update.

    Thank you,

    Rohan

  • 0 in reply to Rohan Patwardhan1
    TI__Mastermind 21720 points

    Hello Rohan,

    I tested the INA302 on the bench and found that each alert only triggers for one specified condition.  The alert only triggers if the output exceeds the set limit pin value.  So technically it can be used for either forward or reverse current.  However, the logic reverses for reverse current, where the alert asserts if the reverse current is blow a value that makes VREF-load*shunt*gain > Vlimit.  So if you are looking for a way to have two overcurrrent alerts for either direction.  Maybe you can reconsider the INA303, but with a DAC connected to the REF pin.  You could by default set the lower warning value limit voltage and use the alert to trigger the DAC to adjust the limit voltage to the higher critical limit value.

  • 0 in reply to Patrick Simmons
    Intellectual 340 points

    Hi Patrick,

    Just confirming whether my understanding is correct with a small example.

    VREF = 2500mV, GAIN = 20, RSHUNT = 1 mohm, DSG_OC = 10A, CHG_OC = -10A. ALERT1 shall be used for DSG_OC and ALERT2 shall be used for CHG_OC

    Using formula from Eqn 3 on Pg19 of datasheet.

    RLIMIT1 for DSG_OC = (2500+(10*1*20))/80 = 33.75kohm

    RLIMIT2 for CHG_OC = (2500+((-10)*1*20))/80 = 28.75kohm

    VLIMIT1 = (80*33.75) = 2700mV

    VLIMIT2 = (80*28.75) = 2300mV

    ALERT1 shall assert to LOW, when VOUT > 2700mV(VLIMIT1). 

    ALERT2 shall assert to LOW when VOUT < 2300mV(VLIMIT2)

    Is my understanding correct?


    Thanks,

    Rohan

  • 0 in reply to Rohan Patwardhan1
    TI__Mastermind 21720 points

    Hello Rohan,

    For the INA303 yes, but not for INA302.  For INA302 you will have:

    ALERT1 shall assert to LOW, when VOUT > 2700mV(VLIMIT1). 

    ALERT2 shall assert to LOW when VOUT > 2300mV(VLIMIT2).