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ISO224: GND1 Pin

May
Genius 9880 points
Part Number: ISO224
Other Parts Discussed in Thread: AMC3330

Hi Team,

My customer planning to accurately measure bi-directional voltage from ISO224 chip in a 3 phase AC motor controller application.

In their application , the motor will be connected in delta/star configuration. How will to get the ground from high side "labelled GND1" 3 phase system especially in delta wiring format where there is no neutral. Does ground 1 always have to be 0. Can you please explain about this.

voltage sensor guide.pdf

Thank you.

  • 0
    TI__Guru 53672 points

    Hi May,

    The ISO224 has two grounds, GND1 and GND2.

    While voltage magnitude of different voltage domains is sometimes relative to 0V (earth ground), let's assume that GND2 is truly 0V (earth ground).

    This is likely where the customers MCU/FPGA/Processor/DSP will be located and the output signals V_OUTP, V_OUTN from the ISO224, GND2 will be relative to 0V (earth ground).

    The high voltage ground, GND1 can float and be up to several hundreds of volts greater than GND2. This specification is the working voltage which can be found in the datasheet. 

    The input signal, V_IN, can be +/-12V with respect to GND1 and as the ISO224 requires a high side supply, VDD1, this must be provided and 4.5V-18V with respect to GND1. 

    We have another cookbook circuit that may help if the customer is interested in sensing Line-Line voltages as well: https://www.ti.com/lit/an/sbaa553/sbaa553.pdf

    Please let me know if you have additional questions and this FAQ links to additional collateral: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1164993/faq-isolated-data-converter-collateral-overview

  • 0
    Prodigy 10 points

    Dear May,

    Thanks for your elaborative explanation.

    Which one do you recommend in measuring AC voltage without neutral using the , is it the ISO224 chip or the AMC3330 ?.

    I see the AMC3330 has the PSPICE library for simulation, does the TMC1100 have pspice library for simulation as well??. This PSPICE will really help in designing.

    Can the internal DC-DC coming form AMC33330 produced 5V used to power a micro- computer?.

    Is the AMC33330 TI newer release chip compared to the ISO224?.

    Very very thankfully,

    Ahmed Ali Mbarak..

  • 0 in reply to Ahmed Mbarak
    TI__Guru 53672 points

    Hi Ahmed,

    Either device can be used for this measurement. Selection should depend on which devices features you prefer.

    The ISO224 would require a high side supply and the +/-12V input range allows for highest SNR and accuracy. The input impedance is lower, 1.25Mohm typ which may benefit from gain calibration.

    The AMC3330 would not require the high side supply and the +/-1V, 1Gohm input voltage range will still produce a very high accuracy measurement and gain calibration may not be necessary, therefor ease of use is greater. The internal DC/DC converter produces 3V on the high side and is currently spec'd to allow for an additional 1mA to other circuitry.

    The AMC3330 (2020) is newer than the ISO224 (2018), but neither device is "old" or at risk of EOL.