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Low ESR Output Capacitor for REF5010 and REF5025

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EPAIII:
I am getting back to a project that I had to put on hold around a year ago. I am trying to build a fairly accurate (0.05%) Voltage reference to use for calibrating analog meters. And I plan to use similar circuitry to produce a current reference of similar accuracy for the same purpose. In my discussion of this project here last year I more or less was convinced that the REF50xx series of Voltage references were a good choice. Perhaps the best choice after I was shown that they could be stacked to produce a chain that would give steps of 10 Volts and smaller steps of 2.5 Volts by adding several of the 2.5 Volt version. With them I can literally have from 2.5 to around 300 Volts at 2.5 Volt steps in one unit. More than enough to check and calibrate most analog meters.

So I am trying to put together a parts list and the REF50xx spec. sheet says that a 1 to 50 uF capacitor with low ESR should be used on the output. It mentions a 1 or 1.5 Ohm value. I assume that lower would be OK. Although the supply houses have excellent search facilities, the ESR does not seem to be among the parameters that come up early in the search process. You need to be down to around 1000 remaining parts before they list it and that slows the search down a lot.

I have dived into lists of aluminum electrolytic, tantalum, and multi layer ceramic capacitors and found that very few aluminum types have ESR specs. at all. Out of hundreds of thousands of types I found only one with an ESR in that range. Cross them out, I guess. But I am finding that tantalum capacitors do have ESRs in that range and many are even a lot lower. And the multi layer ceramics just say they have a low or very low ESR but don't seem to give values. Both have suitable Voltage ratings (16 to 35 Volts in my searches) The prices on both types seem affordable.

So I ask, which should I pick, tantalum or multi layer ceramics? Or should I expand my search?

As always, thanks in advance for any help you can provide.

tom66:
Nothing stops you putting a small series resistor inline with an otherwise inadequate capacitor choice.

David Hess:
The TI datasheet says that the output capacitor ESR must be lower than 1.5 ohms for stability, but lower than 1 ohm will increase noise.  Small tantalum capacitors meet this requirement but an electrolytic capacitor will need to be 10 microfarads or higher.  I suspect a ceramic or film capacitor will cause problems unless a series resistor is added.

EPAIII:
Seems like I need to read the data sheet again. So between 1 Ohm and 1.5 Ohms. That looks like a fairly narrow range. IIRC, it does seem to show a board layout with a series resistor.

I guess the biggest question in my mind at the present time is just what is the ESR of a multi layer ceramic. What do they mean by "low" or "very low"? They seem to include the low ESR in the bullet list of advantages of these capacitors, but list no actual values. I find that rather strange. Perhaps I just need to check more manufacturers' spec. sheets.

Someone:

--- Quote from: EPAIII on July 07, 2022, 04:22:17 am ---what is the ESR of a multi layer ceramic. What do they mean by "low" or "very low"? They seem to include the low ESR in the bullet list of advantages of these capacitors, but list no actual values. I find that rather strange. Perhaps I just need to check more manufacturers' spec. sheets.
--- End quote ---
You need to go past the "family" datasheet/catalogue (which is mostly to show the production parameters) all the major ceramic capacitor manufactures have huge databases of part specific data.

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