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Original question:

AMC3330-Q1: AMC3330-Q1

AMC3330-Q1: AMC3330-Q1

Kunal Pathak
Intellectual 375 points
Part Number: AMC3330-Q1
Other Parts Discussed in Thread: AMC3330, AMC3301-Q1, AMC3301, AMC1300, AMC1301

Hi,

As I got to know that AMC3330-Q1 will be available widely by the end of October, but since we need to freeze our design before that, so can you please suggest an alternate part similar to AMC3330-Q1 for AC line to line voltage measurement application. Attached an application block diagram for your reference.

  • 0
    Intellectual 375 points

    Part Number: AMC3330-Q1

    Hi,

    Can you please suggest any solution (application note) for AC line to line voltage sensing for Three Phase PFC application. A block diagram is attached for your reference.
    I also want to confirm that AMC3330-Q1 is suitable for the AC line to line voltage sensing application?
  • 0 in reply to Kunal Pathak
    TI__Guru**** 175131 points

    Hi Kunal,

    I'll see if we can get you some samples of the AMC3330-Q1 to help you finalize your design.  I don't immediately see anything wrong with your block diagram and believe the AMC3330 will be a good fit for you.

  • 0 in reply to Tom Hendrick
    Intellectual 375 points

    Hi Tom,

    Thank you for the response. We are having many dependencies on this IC so for backup can you please suggest another IC for Line to Line voltage sensing application.

    Regards,

    Kunal Pathak

  • 0 in reply to Kunal Pathak
    TI__Guru**** 175131 points

    Hi Kunal,

    The AMC3330 is currently the only amplifier we have which has a +/-1V input range.  We have the AMC3301-Q1 which has a +/-250mV input range.  Same package as the AMC3330-Q1, just with a lower input voltage range.  We have some other devices with analog output where you would need to provide high-side power as well, so let me know if that is of interest to you and I'll provide some part numbers.

  • 0 in reply to Tom Hendrick
    Intellectual 375 points

    Hi,

    Thank you for the suggestion.

    Yes, we are trying to implement AMC3301 for our design as a backup to AMC3330-Q1, however, we have a few queries related to AMC3301 as follows,

    1). In section 8.2 of AMC3301 datasheet, it is mentioned that the device is used for AC line voltage measurement which contradicts the diagram shown in Fig. 8.1. So could you please clarify whether this IC can be used for High voltage AC measurement (+/- 1000V Line to line).

    2). Do you have any recommendations for sizing the resistor divider network for cross-current calculation for AC voltage measurement since the voltage varies from 0V to peak voltage?

    Could you please provide some reference for AC voltage measurement (to understand the sizing of resistor divider network) for a low impedance device.

    3). Can you please suggest a way to define the accuracy level for an AC voltage sensing. Do you have solutions/ recommendations for the same?

  • 0 in reply to Kunal Pathak
    TI__Guru**** 175131 points

    Hi Kunal,

    I see that Alex answered, or at least started to answer your AMC3301 queries in another post.  In Figure 8-1, the application here is still 'AC Line' - it's just single phase, so I'm not sure that there is a contradiction.  You certainly could use the AMC3301 to measure phase to phase voltage so long as the MAX voltage at the sense resistors were within the limits of the device.  Obviously with +/- 1 V input  versus +/-250mV input there would need to be some modification made to the input sensing side.  With the lower impedance of the AMC3301 versus the AMC3330, the final sense element would need need some additional calibration attention, but overall, yes - it is possible.

    As for the overall accuracy using the AMC3301 versus AMC3330 in this sort of application, I do not have an off the shelf reference design to offer you.  Can you give us a ball park figure of merit as to what accuracy you are looking for?

  • 0 in reply to Tom Hendrick
    Intellectual 375 points

    Hi Tom,

    Can you please suggest some other part suitable for AC voltage sensing with high input impedance, since AMC3301 has low input impedance (19Kohm only).

    Regards,

    Kunal

  • 0 in reply to Tom Hendrick
    Intellectual 375 points

    Hi Tom,

    We observed that the device AMC3301 has got very low input impedance.

    AMC3330-Q1 has got a recommendation of using 0.1mA current (through resistor divider network) for design considerations as the device has high input impedance.

    However, since you are recommending AMC3301 device (having low impedance) for AC voltage sensing could you please suggest input current recommendation for the same device. 

    Also provide information w.r.t. calibration in case we are going with AMC3301.

    Regards,

    Kunal

  • 0 in reply to Kunal Pathak
    TI__Guru 51341 points

    Hi Kunal,

    This application note will explain the necessary calibration:

    Please give this a read and let us know if you have additional questions.

    This excel calculator may be helpful as well:

    You can use AMC1300 or AMC1301 instead of AMC3301. Be sure to look at the differences between the "Differential with R3' " and "Differential without R3' " configurations.

  • 0 in reply to Alexander Smith
    Intellectual 375 points

    Hi Alex,

    Thank you.

    Wanted to confirm that whether we can use the same excel calculator (that you shared) for DC voltage sensing also?

    And can you please share the excel calculator for the current sensing?

    Regards,

    Kunal Pathak

  • 0 in reply to Kunal Pathak
    TI__Guru 51341 points

    Hi Kunal,

    Using the calculator for DC voltage is the same. I'm working on a version for current sensing, however it is not ready for the public yet. Simply use ohm's law for the time being to manipulate the user inputs shown in blue. 

  • 0 in reply to Alexander Smith
    Intellectual 375 points

    Hi Alex,

    Thank you for the response.

    I have a question related to the application note that you have shared, 

    Can we use the same R3 and R3' formula given in section "Design Steps II - Consideration of R3' " (Pg 4) for Line to line voltage sensing (in which we have resistors on both sides of sense resistor, please refer below attached diagram).

    Can you please tell the significance of 2 in the denominator of R3 formula (attached above).

  • 0 in reply to Kunal Pathak
    Intellectual 375 points

    Hi Alex,

    Can you please share the information on how to do the calibration (in voltage sensing excel calculator), as the information is not available in application note that you have shared.

    Also, wanted to know how to calculate GE Rdivider and what is the value of R4 (internal to IC (for AMC3330 & AMC3301)).

  • 0 in reply to Kunal Pathak
    Intellectual 375 points

    Hi Alex,

    Should I consider the Rtop of first-string resistor which is 5Mohms or should I consider 10Mohms (total resistor divider network)?

    Also, can you please give some information on R3' equation.

    Regards,

    Kunal 

  • 0 in reply to Kunal Pathak
    Intellectual 375 points

    Hi Alex,

    I have a doubt in error calculation, i.e. in datasheet the Gain error is different and in excel calculator the error considered is different. Can you please give some information on that.

  • 0 in reply to Kunal Pathak
    TI__Guru 51341 points

    Hi Kunal,

    Thank you for your questions. 

    You can use the same equation, just make sure to include all resistors. The purpose of that portion of the calculation is that is setting the attenuation ratio from the input signal source to the input signal of the input.  If I remember correctly, the 2 is in the equation due to the differential amplifier on the front end of the device. 

    This post should help explain how calibrations are performed: https://e2e.ti.com/support/amplifiers/f/14/p/937333/3463286#3463286

    GERdiv = R4/(R4+RdivImpedance); R4 = 12.5k for AMC3301 and 1M for AMC3330

    For the R3' equation, the purpose of R3' is the balance of the input bias current offset in addition to the gain error created by the sense resistor in parallel with the differential input impedance. 

    Thank you for pointing out these data entry errors, I will get them updated. 

  • 0 in reply to Alexander Smith
    Intellectual 375 points

    Hi Alex,

    From the recently shared calibration document, we understand that we need to individually do this calibration process for each IC. Please confirm.

    Is there any other direct way to calibrate the device apart from what is described in the document? It would be helpful if you can share that as well.

  • 0 in reply to Kunal Pathak
    TI__Guru 51341 points

    Hi Kunal,

    You would want to do the calibration on each system, not just the IC, such that the entire signal chain is calibrated. 

    Some devices have internal calibration features, but for the isolation devices, this is the only way. 

  • 0 in reply to Alexander Smith
    Intellectual 375 points

    Hi Alex,

    Thank you for the response.

    Regards,

    Kunal

  • 0 in reply to Alexander Smith
    Intellectual 375 points

    Hi Alex,

    Can you please share current sensing excel calculator, if possible.

    It will be helpful as we are doing worst-case analysis.

    Regards,

    Kunal

  • 0 in reply to Kunal Pathak
    TI__Guru 51341 points

    Hi Kunal,

    I'm still finishing up a few things with the new calculators - hoping to have them online next week. 

    For the time being, you can use the voltage sensing calculator as a current sensing calculator by manipulating the values in the blue entry cells using ohms law. 

  • 0 in reply to Alexander Smith
    Intellectual 375 points

    Hi Alex,

    Can you please share the current sense error calculation tool/ Excel sheet, once it's finished from your end.

    Regards,

    Kunal

  • 0 in reply to Kunal Pathak
    TI__Guru 51341 points

    Hi Kunal,

    Yes of course. Anything you're having difficulty with using the current version of the calculator?