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AMC1300: Significant Gain Error

Yuto Kitamura
Expert 5200 points
Part Number: AMC1300
Other Parts Discussed in Thread: AMC1311,

Dear team,

My customer is evaluating the AMC1300 for voltage sensing and get a problem. Please ignore using AMC1300 for voltage sensing we understood that AMC1311 is better.)
Please refer to the image below. 

They are measuring V1 and V2 to find the reason of the system issue. And the result was, V1 = 0.011V and V2 = 0.087V. From them Gain would be V2/V1≒7.91.
It is significantly different than datasheet fixed value (= 8.2±1%_max).

  • Could you please give us the expected cause of the issue and help to resolve it?

Best regards,
Yuto

  • 0
    TI__Expert 5975 points

    Hi Yuto,

    There are a few things that could be causing this.

    • Gain error is affected by temperature, what temperature is your customer operating at? These figures are given at temperature = 25°C. (See section 7.13 for more information)
    • I cannot tell from this screenshot if the customer is shorting INN to GND1. This is something we recommend doing in the power supply recommendations (section 10 of the datasheet). If this is not grounded, the power supply could be floating. This also defines the common-mode input voltage.
    • Does your customer have an RC filter in front of the amplifier? Knowing what circuitry is in front of the device could help me determine the error. There is an example filter design in section 9.2.2.2 for reference as well. 

    Please let me know if any of these suggestions help.

    Best regards,

    Eva

  • 0 in reply to Eva Mason
    TI__Expert 5200 points

    Hi Eva,

    Let me send you the total circuit internally. You can find INN is not tied to GND and the filter.

    Best regards,
    Yuto

  • 0 in reply to Yuto Kitamura
    TI__Expert 5975 points

    Hi Yuto,

    Just responded to your message internally. Closing this thread for now.

    Best regards,

    Eva