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AMC1302: Wiring of the INN and GND1 terminal for measuring DC bus current in the circuit.

Sudhanva Gokhale
Prodigy 40 points
Part Number: AMC1302
Other Parts Discussed in Thread: AMC3302

Tool/software:

I was using AMC1302 for bus current measurement of 0-25A. The INN terminal and the GND1 terminal are always shown to be connected in the datasheet. In my circuit the IGBT 'Driver GND' is the same as the 'Power Ground'. 

1. So, by adding a sense resistor on the high side in series and wiring the sense resistor +voltage terminal to the INP pin and resistor - voltage to INN and GND (Power Ground), am I applying the entire Vbus across the small sense resistor?

2. If I am indeed applying the entire voltage across the sense resistor, what is the work-around to measure the current using AMC1302?

Please assist.

  • 0
    TI__Guru**** 182301 points

    Hi Sudhanva,

    Welcome to our e2e forum! 

    1.) Yes, and VCM might be an issue based on the DC bus voltage.

    2.) See comments below...

    The issue I see with your current schematic is that essentially you are shorting out both IGBTs.  What is the voltage across C_bulk?  For this high side application to work correctly, you would need an isolated power supply for VDD1 that is 3.3V to 5V above the voltage relative to the drain of M1.  You could do low side measurements with this power supply configuration by placing the shunt in the return path of the LCR load if you remove the ground connection between the R and source of M2.  One potential alternative to the AMC1302 is to use the AMC3302, which derives the high side power rail from the low side power source.  Check that part out and let us know what you think.

  • 0 in reply to Tom Hendrick
    Prodigy 40 points

    Thanks for the quick response, I will take a look at the AMC3302 part. Also the Bus voltage would be 350VDC to 360VDC

    1). I was looking at low side measurements too. But I don't understand what you mean by "if you remove the ground connection between the R and source of M2". I will draw a revised schematic and we can clarify if we mean the same thing.

    2). I was actually looking at designing a Full bridge circuit as well, I will attach a picture with a low side configuration with the AMC1302.


    Please let me know if the Full-bridge would work.
    Thanks.

  • 0 in reply to Sudhanva Gokhale
    TI__Guru**** 182301 points

    What I meant was the ground symbol - you have it on both sides of the shunt, you only need it on the one side.