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AMC1301: How to use AMC1301 to measure line-line voltage

Wayne Wang20
Expert 4360 points
Part Number: AMC1301
Other Parts Discussed in Thread: AMC1300, AMC3330

Hi team,

My customer wants to use AMC1301 to measure line-line voltage, for example, the voltage between U and V. Please note U, V, W are three phase gird voltage.

Customer schematic is as below picture. 

For differential voltage between VINP and VINN, it is 1k/(4M+1k)*(U-V) which is within AMC1301 +-250mV differential input range.

But for common mode input voltage, as U and V are isolated from +5V1GND, so how could we determine whether (VINP+VINN)/2 is within (-0.16~VDD1-2.1) range? 

And do you have any better way to measure line-line voltage? Thanks.

Best regards,

Wayne

  • 0
    TI__Mastermind 47625 points

    Hi Wayne,

    As you've pointed out, measuring line-line voltage can be challenging due to managing the input common-mode voltage magnitude. Typically, the best way to ensure that the inputs are within the common-mode range is to have a common ground that all phases are tied to.  

    The main issue that I see with this particular application is "U and V are isolated from +5V1GND". This would be an issue even for a single-phase measurement. Does this system have a neutral connection? If so, the neutral could be tied to +5V1GND, which could be the common-point.  

    Do you have any additional information you can share about how +5V1 is generated? 

    If possible, please promote AMC1300 in place of AMC1301 as it is a newer pin-pin compatible device. However, both of these devices have a low input impedance that is not ideal for voltage measurements. 

    If your customer is not aware of our devices with integrated DC/DC converter allowing for single-supply operation, please promote AMC3330. This device has a high input impedance which is ideal for voltage measurements. 

     

  • 0 in reply to Alexander Smith
    TI__Expert 4360 points

    Hi Alex,

    Thanks for your reply. For the +5V1 network, it is generated from a 5V-5V isolated power module PDL03-05S05. So +5V1 and +5V1GND are totally floating networks. I will double check with customer if UVW has a neutral point. Thanks.

    Best regards,

    Wayne

  • 0 in reply to Wayne Wang20
    TI__Mastermind 47625 points

    Hi Wayne,

    Happy to help! 

    The power supply GND +5V1GND will need to be referenced in some way to the voltage to be measured. If this is difficult for their application, please promote AMC3330. The AMC3330 has an internal DC/DC converter which can help simplify the design.