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ISO124: Isolation amplifier damaged, simple connection setup

David Matias77
Prodigy 20 points
Part Number: ISO124

Good day,

I am using a ISO124 with two switching power supplies both +-12V DC, at the input of the ISO I have a range of 0-5V DC and the 0V reference grounded, at the output I have a ADC (a PLC analog input card) connected with a 100kohm impedance, and the 0v not grounded but referenced to 0 v of the switching power supply 2, all the capacitors on the power supply of both parts are connected, and I have a protection zenner at the input (7V), but after a while the IC starts warming and eventually got damage, we are out of ideas why is happening, the connection is too simple.

Thanks

  • 0
    TI__Guru**** 181021 points
    Hi David,

    Welcome to the e2e forum! Can you attach a schematic of your board for the ISO124 and perhaps give a little background on what your application is? Can you give any detail on the damage you see? Does the output just stop? Is the part heating up till the point of failure? Are you able to monitor the high and low side power rails with respect to their current consumption?
  • 0 in reply to Tom Hendrick
    Prodigy 20 points

    Tom, I don't have the schematic in my hands right now, but here is the circuit, In Vin we have a zenner between Vin and GND1, and in the out put irs directly connected to a PLC analog input card Vout and GND2,

    for our application we are building a high voltage test station, we use 5000 V ac in one of our tests, and the others are around 1000Vdc, but since this is an automatic test machine we a re using a PLC to control the sequence, we already have voltage measures in the same points where the input of the iso is connected, and the signal is not affected by his 200kohm impedance, so the voltage divisor where we take the sample is already adequate with ac to dc converters and filters.

     

  • 0 in reply to David Matias77
    TI__Guru**** 181021 points
    Hi David,

    So what is the voltage potential between GND1 and GND2? Is it the 1kV to 5kV mentioned above? Are you able to measure the supply currents?