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INA138-Q1: Variation data of internal resistor

Part Number: INA138-Q1
Other Parts Discussed in Thread: INA138

Hi Team,

1. Is there any variation data of internal resistors(5kohm) at room temp?

2. Is internal resistor affected by ambient temp? If so, is there any data?

3. Is there any data about resistance between two internal resistors? (%)

Regards,

Kotaro Yamashita

  • Hello Kotaro,

    1. No. Any data that would reflect variation of the resistors' values is data showing the variation in transconducatnce (gain) and offset (Vos); although, gain and Vos vary over temperature due to other reasons. Since the INA138-Q1 datasheet shows the gain and Vos for temperatures -40C to +125C, then you be assured that at 25C the device will meet specifications. If you want gain and offset data strictly at 25C, you could look at the datasheet for the INA138. However, these are technically not the same product so TI cannot guarantee that the INA138-Q1 at 25C will have the same variation as the INA138 at 25C since we only spec the INA138-Q1 from -40 to +125C. This is why it is an Automotive Qualified part. We spec it over the entire range.

    2. No. The internal 5kOhms resistors are trimmed match each other. If they mismatch each other, then this would reduce the gain and Vos overall by the same amount for all temperatures.

    3. No, but you could calculate that the differential input impedance is 5kOhm with the following:

    From datasheet:
    Iout = gm*Vsense = Vsense/5kOhm

    From datahsheet block diagram:
    Rin_diff = Vsense/(Iout +Ib+ - Ib-); Ib+ =Ib- = Ibias
    Rin_diff = Vsense/(Iout)

    Therefore,
    Rin_diff = Vsense/(Vsense/5kOhm )
    Rin_diff = 5kOhm


    Best Regards,
    Peter Iliya
    Current Sense Applications