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MPY634: Ask For Typical application circuit for Calculate RMS Value.

Brian Li
Genius 9895 points
Part Number: MPY634

We wanted to replace the AD734 of ADI, and we don't know if the MPY634 has a typical application circuit that achieves square sum, open root, and rms.

The following diagram is a typical application circuit for the AD734, can we do the same with one circuit?

  • +1
    Guru 140200 points

    Hi Brian,

    this may interest you:

    IMEKO-TC4-2017-068.pdf

    Kai

  • +1
    TI__Guru* 93105 points

    Hello Brian,

    The MPY634 is closer in functionality to the AD534 4-quadrant multiplier than it is to the AD734. An key and important difference between the MPY634 and the AD734 is the direct denominator control function (U0, U1 and U2) needed for the RMS to DC application circuit you have shown.

    Kai has graciously provided a reference to an alternate circuit topology that employs the MPY634 in an RMS to DC application. That is an option.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to kai klaas69
    TI__Genius 9895 points

    Thank you Kai. But I wonder can we  achieve this function with only one MPY634?

  • 0 in reply to Thomas Kuehl
    TI__Genius 9895 points

    Thank you Thomas. And can you tell me if we have a  product which is closer to the AD734 in functionality than MPY634?

  • +1 in reply to Brian Li
    TI__Guru* 93105 points

    Hi Brian,

    We often receive requests for a one, or a minimum chip, RMS to DC conversion solution. The simple answer is TI does not have such a product, or have a simple solution to offer. The prior existing RMS to DC converter solutions available from Burr-Brown and National Semiconductor, both acquired by TI, have long been discontinued. That has left the AD and LTC (now AD) solutions as the most viable from a simple application standpoint. The circuit that Kai provided using two MPY634 multipliers and op amps is one of the lower chip count circuits I've seen using that device in the application. 

    Unfortunately, we do not have anything equivalent to the AD734 to suggest.

    Regards, Thomas

    Precision Amplifiers Applications Engineering