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INA225-internal resistances

tsuyoshi tokumoto
Expert 2630 points
Other Parts Discussed in Thread: INA225, INA282

I'm Tokumoto, Marubun from Japan.
I have a question on INA225.

Our customer is designing a circuit using INA225 now.
He intends to  design REF power supply with the resistance division from a power supply for cost reduction.
I'd like to know the internal resistance value (from IN- to OUT and from IN+ to REF : 25V/V, 50V/V, 100V/V, 200V/V)  to estimate the error by external resistance(REF pin).

 Best regards.

  • 0
    TI__Genius 14825 points
    ,
    The thing about the resistors internal to the current shunt monitors is that the absolute value of the resistors can vary +/- 30% on most processes. The resistor pairs that define the gain are trimmed to have excellent matching, so the gain factor is very accurate while the resistance is less so. For that reason, we suggest buffering the divided-down reference voltage, as shown in figure 43 of the INA225 data sheet.

    Another product to consider is the INA282 family, which has an internal 50/50 voltage divider for the reference. I don't know the design requirements of the system the customer is building, but it's an option.

    If they still want the target values for the resistors, I may be able to get those, but at +/- 30% allowable error in the absolute value, I don't know how much good it will do them to attempt to calculate error contribution.