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INA3221: Programming alert limits

Eugene Rak
Prodigy 10 points
Part Number: INA3221

I have a problem figuring out proper way to set up alerts on ina3221. on datasheet is says that those alerts are current driven not voltage driven , however examples are giving only to set up for voltage sensing. 

1) Can you confirm that alerts are current driven ( warning, critical NOT power valid limits) ? if alerts are current driven how can it be set up ( please give example to calculate it). 

2)  If it voltage driven how to set it up lets say to 9 volts. 

thank you 

  • 0
    TI__Mastermind 21785 points
    Hello Eugene,

    Thanks for considering to use Texas Instruments in your design. These devices measure current that is running through a shunt connected to the IN+ and IN- pins. The current through the resistor generates a voltage across the resistor. This voltage value is then stored in the shunt voltage register. So this is why you may see examples of a voltage source placed between the input pins.

    Say you want set a warning at 1A with a system max of 1.5A. You can calculate the needed shunt by taking the max vshunt voltage and dividing by the max current to get 0.1638V/1.5A = 109.2mohm. From that point you can choose a larger resistor 110mohm and have a max measureable current less than 1.5A or you can use a 100mohm and have a max measurable current of 1.638A. In this case, I will use the 100mohm. Based off of this value, I will then set the warning and critical values. In this case for a warning to be triggered at 1A, the shunt voltage will need to be 0.1V. If my critical current was at 1.2A, the shunt voltage at that current level will be 0.12V. For the warning register, your value would be 0.1V/40uV = 2500 (9C4h), while your critical would be 0.12/40uV=3000 (BB8h).