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AMC1300: Isolation Amplifiers

manoj r
Intellectual 260 points
Part Number: AMC1300
Other Parts Discussed in Thread: AMC1311, AMC1336, TIDA-00445

hii..

In isolation amplifiers AMC1300, AMC1311, AMC1336 is there any advantage of making negative terminal and GND as common. Shall we use the Differential input and supply GND separately. So that I can have a single power supply for Three phase Grid Voltage measurement ?? Please note Neutral is not available in our configuration.

Regards

Manoj.R   

  • 0
    TI__Mastermind 47595 points

    Hi Manoj,

    The negative input pin and the GND of the device should be connected to ensure that the input measurement remains within the common-mode input of the device. The exception here is that the AMC1311 in a single-ended device. The power supply for the device should be +3-5V with respect to the device GND and the input voltages should be +/-250mV for AMC1300, 0-2V for AMC1311, or +/-1V for the AMC1336 with respect to the device GND. Since the device GND is "floating" with the measurement, the voltage supply must "float" with the measurement as well. Thus, using 1 power supply to supply 3 devices measuring 3ph AC voltage will not work. 

  • 0 in reply to Alexander Smith
    Intellectual 260 points

    Hi Alex,

    Shall we create a star point using resistance and make supply GND, Star GND , Negative terminal of Iso amplifier as common. And hence using single power supply shall we able to measure three phase Phase voltage grid voltages.??

    Regards

    Manoj.R 

  • 0 in reply to manoj r
    TI__Mastermind 47595 points

    Hi Manoj,

    I believe you are referring to making a star connection to the center of a delta configuration to make a floating GND? If so, implementing this is possible - however I have not verified it's performance.

  • 0 in reply to Alexander Smith
    Intellectual 260 points

    Hi Alex,

    Thanks for the clarification. Shall we adopt same as TIDA00555 design. The only difference we will create star point in the board.

    Also is there any specific advantage having an isolated power supply for shunt current sensing method??

    In TIDA-00445 design  an isolated power supply is used for current sensing whereas TIDA 01420 and other similar designs uses non isolated power supply. Any recommendations on the same please??



    Regards

    Manoj.R

  • 0 in reply to manoj r
    TI__Mastermind 47595 points

    Hi Manoj,

    If an isolated current sensing measurement is being performed with an isolated amplifier, then the power supply for the amplifier will need to be isolated as well such that the circuitry on the low side of the barrier is protected. 

  • 0 in reply to Alexander Smith
    Intellectual 260 points

    Hi Alex,

    My doubt is on the primary side of the isolation amplifier. For measuring current through shunt resistor supply required for isolation amplifier is created from Top Gate Driver supply +15V to +5V. Also there are reference designs to generate isolated power supply from the gate driver supply. Is there any advantage to have isolated GND for isolation amplifier power supply from the gate driver TOP device supply ??

    Regards

    Manoj.R

  • 0 in reply to manoj r
    TI__Mastermind 47595 points

    Hi Manoj,

    I see now, I didn't understand the original question. If the high side power supply for the isolation amplifier is being derived on the high side of the barrier, then additional isolation is not necessary. 

  • 0 in reply to Alexander Smith
    Intellectual 260 points

    Hi Alex,

    Thanks for the clarification. 

    Regards

    Manoj.R