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ISO124: ISO124

Part Number: ISO124
Other Parts Discussed in Thread: ISO224


I am going to design a circuit to isolate the ground between 2 sides. So, i planned to go with ISO124. I have some queries related to it.

Input Voltage range : 0V to 10V

Power supply: there +12V supply available , using that isolated +12V can be generated.

Can i connect GND1 and -VS1 together(connect to +12V GND), since my power supply is only +12V.

Similarly at output side also can i connect GND2 and -VS2 together and connect to Isolated +12V GND?



  • Hi Kannon,

    Unfortunately the ISO124 won't work properly without a negative supply (at least -5V) on each side of the isolation barrier.  Do you need the wide body package associated with the ISO124?  If not, please take a look at the ISO224.  You can get your 0-10V input and it only needs a single 5V supply on the high side.

  • Hi Tom,

    Thanks for the reply.

    I have looked in to ISO224. The output of ISO224 is differential.

    For our application, we need single ended output from isolated amplifier and the output voltage should be same as the input voltage.

    Does it possible by adding any additional circuit to ISO224? if yes, does it require any additional power supply other than +5V?

  • Hi Kannon,

    Take a look at the EVM User Guide for the IS0224EVM (Figure 6, page 8).  There is a differential to single ended circuit example with a gain of 3 so you get the same output voltage as what you apply to the input.  For the OPA on the output, you would need your 12V supply in order to get 10V out but the ISO224 would only need the 5V supply.

  • Hi Tom,

    In IS0224EVM user guide page 4 typical voltage for J5 is mentioned as +/- 15V. If we use only +12V supply. Is it okay to connect Pin 2 (GND2) and 3(VSS) to +12V power supply GND to support for 0 to 10V analog voltage range?

  • Hi Kannan,

    J5 is used to power the differential to single ended output stage.  If you are only using the positive voltage, yes, you could tie pin 3 to GND2.  The only issue there is that you may not get all the way down to 0V on the output - the amplifier will require some headroom.

  • Hi Tom,

    For 0V input, maximum what would be the voltage at U4 pin 6 or at J4 connector?

    If we use dual power supply (+/- 12V), For 0V input, what would be the maximum deviation at the output of U4?

    Do you have a simulation file for IS0224EVM?

  • The opamp on the differential to single ended stage can get within 500mV of ground.  Let me see if I have a TINA circuit to share.