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[FAQ] ISO224: Tying ISO224 OUTN to GND2

Intellectual 340 points

Replies: 4

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Part Number: ISO224

This might be a silly question, but is there any problem that might arise when tying the negative output of ISO224 to the low-side ground, GND2? My original plan was to do this because the microcontroller that I'm using will be referenced to the same low-side ground (MSP432P401R launchpad), so the output is essentially "single-ended," if you will.

However, this is not the route that the datasheet specifies (or the EVM for that matter). It seems that the output is used differentially in these applications.

Regards,

Michael Wu

  • Hi Michael,

    Not a silly question at all! A silly question would be "Why did the chicken cross the road?"

    The ISO224 is a true differential output amplifier so you cannot simply short the (-) output to ground. You could use the (+) output only and terminate the (-) output with 10K to GND2, but that only gets you half the dynamic range. I'd rather see you do a differential to single ended conversion like we did on the ISO224EVM.

     

    Regards,

    Tom

  • In reply to Tom Hendrick:

    Thanks, that's really helpful. My issue's almost resolved, but which output buffer is preferable from the EVM? OPA277 or TLV6001?

    Since my launchpad is powered by a 5 V source with its own ground that all inputs need to be referenced to, would I need to use TLV6001 since it can be operated with a single-ended supply (as in the EVM), or can OPA277 also be operated using a single-ended 5 V supply?

    -- Michael

  • In reply to michaelwu:

    Hi Michael,

    If you are using this with a Launchpad, I would stick with the TLV6001. There is a 5V rail on the launchpad, but I suspect you would have some ADC Input restriction of ~3.3V.

     

    Regards,

    Tom

  • In reply to Tom Hendrick:

    Thanks Tom. I was looking at the datasheets for both amplifiers and came to the same conclusion since TLV6001 is a R2R amplifier. Thanks for all of the help.

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