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Analog isolation IC or other product, suggestion needed

Leonardo Callegaro
Expert 1605 points
Other Parts Discussed in Thread: AMC1301

Hi There,

I am quite new in this area and I am just wondering if anyone can suggest some product, IC, or circuit. In my application I have some hall effect LEM sensors, each giving an output current (named IS in the picture below) from 0 - 30mA. This current is then going through a control board, where it is converted to a voltage +/-10V (via the resistor RM in the picture below), then scaled down to 0/+3.3V and sent to the ADC input of a C2000 Texas Instruments control card (the last part is not shown below). The sensor circuit is shown below. 

I wanted to ask you if there is any device or IC which is able to provide galvanic isolation for the sensed current IS. I have schematically shown such isolating device inside the yellow box in the picture below. In fact, if the galvanic isolation in the yellow box below was not there (i.e. imagine connecting SMA START+ directly with SMA END+, and SMA START- directly with SMA END-), then the ground of the sensor supply GND1 will be connected with the ground of the control circuit GND2 (via the connecting cable return) and this would generate a problem in my circuit. I cannot change the ground configuration, or the sensors, in my circuit so I need to look into an isolating device as depicted inside the yellow box.

 

Any simple suggestion you have would be great.

Thank you very much in advance.

Leo

  • 0
    TI__Guru**** 180941 points
    Hi Leonardo,

    The LEM sensor is actually providing you with galvanic isolation already, do you need more than that? Normally, the power supply to the LEM and the sense resistor (+/- UC and the Rm noted in the datasheet) are on the user side of the voltage to be measured. If you do need additional isolation, you would still need to put the Rm resistor on the 'M' terminal of the LEM sensor and then you could feed that into an isolation amplifier like the AMC1301 (assuming Vout from the sensor is <+/-250mV).