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OPA2171: Output Accuracy Problem with AC sensing circuit

Brian Wang0928
Genius 15330 points

Part Number: OPA2171
Other Parts Discussed in Thread: OPA2316, OPA2314

Customer is using OPA2171 on the AC sensing(110Vrms) circuit for PV application.

However, we found there is 20mV difference on the VST-DCOS when using different supply voltage of 12VCC or 3.3VCC.

What's the parameter of the OPA to cause the difference? any similar OP suggestion with p2p compatible?  Is LMV822Q1 ok or not?

OP requirements: -40 to 125degree, SOIC.  

  • 0
    TI__Genius 15410 points

    Hi Brian,

    Does the input voltage to the op amp ever go above 1.3V? If so, the common mode voltage is likely the culprit. The common mode voltage on a 3.3V supply only goes up to 1.3V. 

    For an op amp suggestion, do you need the device to operate on a supply voltage from 12V to 3.3V?

    What will be the input voltage (common mode voltage)?

    Thank you,

    Tim Claycomb

  • 0 in reply to Tim Claycomb
    TI__Genius 15330 points

    Sorry, I’m confused with your reply. Why VCC can not be supplied with 3.3V with this circuit? What is the parameter causing the accurate problem?

    If 3.3V is only supply voltage, what OPA you suggest? Is LMV822 ok ? What else? Thanks!

  • 0 in reply to Brian Wang0928
    TI__Genius 15410 points

    Hi Brian,

    Sorry for the confusion. When operating on a 3.3V supply the common mode voltage can only go up to 1.3V, going above 1.3V may be causing the increase in offset voltage you are seeing.

    I recommend taking a look at the OPA2316 or the OPA2314 for a device to use on a 3.3V supply.

    Thank you,

    Tim Claycomb