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REF30XX precision voltage reference decoupling

Anthony Andriano
Prodigy 60 points
Other Parts Discussed in Thread: REF3020

The datasheet recommends a 0.47uF decoupling capacitor for the REF30XX (specifically REF3020 in my case). I'm wondering why that particular value was recommended instead of, say, 0.1uF, which is more common. Using a 0.47uF capacitor would add a line item to my BOM, which I don't want to do unless there's a good reason. I've already prototyped the board with 0.47uF capacitor and the reference works very well. However, it also appears to work well with 0.1uF. I know the impedance of the capacitors is slightly different, but I don't know if that will matter for the internal operation of the part. The datasheet doesn't provide many details other than a recommended value.

Any information would be greatly appreciated.

  • 0
    Guru 21975 points

    Anthony,

    Your 0.1uF decoupling capacitor should be okay if it is placed near the REF3020.. I suspect that the author of this data sheet chose this value based on what was used on characterization circuit boards. Or perhaps they just wanted users to take the decoupling issue seriously. Assuming that you have a reasonably "clean" input supply voltage and adequate decoupling capacitors elsewhere in your system, I'm confident that you will have no problem.

    As some defense, I'll say that if we don't make a specific recommendation for decoupling, we sometimes are asked what value we recommend. We can't win. :)

    Regards, Bruce

  • 0 in reply to Bruce Trump
    Prodigy 60 points

    I'm sure there was a reason, but it probably didn't matter enough to go into further detail in the datasheet. I characterized the voltage with both capacitor values on my board. I was not able to tell a difference, so I figured it would be fine either way. Thanks.