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INA271: What is the maximum error rate of INA271?

Kazuya Nakai59
Guru 21915 points
Part Number: INA271
Other Parts Discussed in Thread: INA281

Hello guys,

One of my customers is evaluating INA271 on their own PCB for their new products.

They compared two INA271 output voltage on same PCB when the differential voltage between IN+ and IN- is 3.8mV.

One of INA271 output voltage was 70mV and another was 110mV. I think the ideal output voltage with the condition is 20*3.8mV=76mV.

So the 70mV is near by the ideal output voltage. But the 110mV is big difference from the ideal voltage.

At this moment, they have the following questions.

Could you please give me your reply for them?

Q1. Is the 110mV output reasonable as the error rate (variation) of INA271?

Q2. If the customer want to know the maximum error rate (variation) at 3.8mV differential voltage, is there any way to know it?

Your reply would be much appreciated.

Best regards,

Kazuya.  

  • 0
    TI__Expert 6330 points

    Hello Kazuya,

    Thanks for the question and using the E2E forum.

    Because the customer is attempting to measure a differential voltage of 3.8mV, it's very likely their measurements would fluctuate around the measurements you're showing. The INA271 has a maximum offset voltage of 2.5mV, so an output voltage of 110mV could be perfectly reasonable. If we do the math, 110mV / 20 = 5.5mV, so it's very possible the offset could be 5.5mV - 3.8mV = 1.7mV. Likewise, the offset could be negative, which explains the 70mV being lower than the expected 76mV.

    A couple of options for the customer to consider could include increasing the size of the shunt resistor to increase the voltage drop at the lower end of their measurement (but with the drawback of increasing the power dissipated by the shunt), or selecting a different Current Sense Amplifier with much lower offset. One example is the INA281 that has a maximum offset of only 0.5mV at room temp.

    Louis