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LDO Output Cap - Changing Tantalum to Ceramic
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Psi:
What sort of tests should i do to an LDO to confirm it is not operating right on the edge of stability.
And confirm it won't go unstable in the field.

I have a LM2937-5.0 reg with 33uF 6.3V tantalum in a product and it has been 100% reliable.
https://www.digikey.com/product-detail/en/avx-corporation/F930J336KAA/478-8172-1-ND
https://www.digikey.co.nz/product-detail/en/texas-instruments/LM2937IMP-10%2FNOPB/LM2937IMP-10%2FNOPBCT-ND

But i have been sourcing and soldering the tantalums on myself because tantalums scare me a bit and i don't trust china PCB fabs to put quality tantalums on my boards.

I want to change to using general ceramics that i can trust china to source and place.
Maybe multiple ceramics in series for higher ESR,  or a cap + resistor.

I have seen this reg go unstable with a single ceramic in the past, so i know it can be an issue.
I want to make sure it has been fully tested and is stable, what tests should i run?

Thanks.
Paul Bryson:
What I do to check regulator stability is to apply a step load change and a step change of the input voltage.  You'll want to check at various loads from minimum expected load to maximum.
I want there to minimal change in the output voltage and little to no ringing.
ANTALIFE:
How about looking at the power up/down transients at "no-load" and 10mA, 100mA, 1000mA...
T3sl4co1l:
Doesn't obviously look like it should have problems.  They do make a point of saying "less than 3 ohms", which includes very small values.  It's not obvious how small though, or if other conditions can exacerbate it (like input or output side resonances).

In any case, the dumb and obvious cure is to simply put a resistor in series with the ceramic cap.  I've done it plenty of times myself. :)

Tim
Psi:

--- Quote from: T3sl4co1l on February 17, 2020, 05:31:28 am ---It's not obvious how small though

--- End quote ---

It does spec a min ohms in another page of the DS

The output capacitor, COUT, must have a
capacitance value of at least 10 µF with an ESR of at least 10 mΩ, but no more than 3 Ω
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