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INA233: Asking for the INA233 OC setting

SHH
Mastermind 32206 points
Part Number: INA233

Hi Team,
customer uses INA233 to monitor 5V power.
here are the conditions.

Vs:3V.
monitor 5V.
max current :0.5A.

could you please verify the CAL and OC register is ok or not?

1. current_LSB=0.5/(2^15)=15.25uA. set 0.03mA/bit
CAL =0.00512/(0.03mA*20mohm)=8533d=2155h

so register 0xD4=2155h


2. calculate register 0x4AH
m= 1/0.03mA=33333
X=0.5A
b=0
R=0
Y=(m*X+b)*10^R=(33333*0.5+0)*10^0=16667=411Ah

so 0x4A=4118h. (ignore LSB 3bit)

I am not sure why R=0 in the datasheet example.
Can you please provide your comment for this 0x4H setting?

customer would like to alert pin to send trigger if reaching the OC limit. please confirm 0xD4 and 0x4A setting are correct and any register need to further set.

BR,
SHH

  • 0
    TI__Mastermind 34260 points

    Hi SHH,

    Your math is correct.

    However as the data sheet suggests, you might want to use a different current LSB to make the math easier and results more accurate. Alternatively you can preserve accuracy by shifting bits. For example, you can use m=333333, which requires R=-1.

    An LSB of 0.05mA instead of 0.03mA will produce an integer m, which does not require bit shifting in order not to lose accuracy. Therefore R can be ‘0’. It works out such that m=20000, R=0 and Cal=5120. A max 0.5A corresponds to Y=10000 for the limit register. That’s all you need in order to trigger an over current event.

    Regards, Guang

  • 0 in reply to Guang Zhou
    TI__Mastermind 34260 points

    Hi SHH,

    Since this thread has gone offline and taken care of through emails/calls, we’ll close it. Please let me know if you have further questions.

    Regards, Guang