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ISO124: Best isolation amplifier for my application

Shad Steigerwalt
Prodigy 20 points
Part Number: ISO124
Other Parts Discussed in Thread: ISO224, AMC1411, AMC3330

I need to take a continuous voltage measurement of approximately 60-260VDC, pass it across an isolation boundary of at least 1500V, and then create an analog representation of this voltage on the other side of the isolation boundary. I have a +15V rail available on the output side. I'm looking at using an isolation amplifier that allows me to utilize the full 15V at the output to hopefully increase the accuracy when scaling the voltage. Could I use this part to scale the input voltage between 0V and 15V on the output side? 

Is there a different isolation amplifier that you would recommend or is there a different part that I should consider?

  • 0
    TI__Guru 51211 points

    Hi Shad,

    While the ISO124 is an older device, it remains very popular due to the wide output voltage range and the wide-body package. Are you expecting a high magnitude of common-mode noise in the system that is driving this requirement?  

    We do have three additional, newer, options to consider. However they cannot support the same wide output voltage range:

    ISO224: this device has a wide input voltage range, +/-12V, highest accuracy, internal charge pump on the high side to allow for VDD1 range: 4.5-18V and +/-4V differential output voltage swing. 

    AMC1411: 0-2V high impedance, input voltage range with differential output and 14mm package for the highest isolation ratings. We also have this device in an 8.5mm package, the AMC1311B.

    AMC3330: +/-1V high impedance input voltage range with +/-2V differential output and internal DC/DC converter which simplifies the design. 

    Please let me know if you have any questions.  

  • 0 in reply to Alexander Smith
    Prodigy 20 points

    Hi Alex,

    This is a redesign and the old system used approximately 0-26V. I was trying to use a similar range with a device that would support 0-15V.

    Can I use the ISO224 as a single ended output? I want to use just the noninverting output.

    Thanks,

    Shad

  • 0 in reply to Shad Steigerwalt
    TI__Guru 51211 points

    Hi Shad,

    Yes, you can just use one output. Of course, this will result is losing some common-mode noise rejection and accuracy. 

    I recommend terminating the other output to ground through a 10kohm resistor as it's a driven output. 

  • 0 in reply to Alexander Smith
    Prodigy 20 points

    Hi Alex,

    Is there a way to predict how much accuracy would be lost by using just one output?

    Would it be worth considering using the ISO124 for the single output?

    Thanks,

    Shad

  • 0 in reply to Shad Steigerwalt
    TI__Guru 51211 points

    Hi Stad,

    From a datasheet calculation perspective, not a significant decrease in performance. 

    It would be dependent on how much noise is in the system and couples to the single-ended output. ISO124 will have this issue as well, however since the output swing is larger, SNR will be affected less compared to only using a single output from the ISO224.