Tool/software:
I am getting the attached ripple on a TPS76912DBVR. Magnitude is ~250mv from 1.028V to 1.276V. Purple is output. Yellow is 3.3V input. I expect the load is quite low <40ma. Output capacitance is 4.7uf X7R ceramic.
What can I do to resolve it?
Marc
us
Hi Marcus,
TPS769 is an older device which is not intended to be stable with ceramic output capacitors unless there is a series resistor added to boost the effective ESR. So from the description of your application setup it is very possible that the LDO is unstable in your configuration.
Below is the section from the datasheet that describes output capacitor selection, I've underlined the relevant section. I would suggest that you swap for a tantalum capacitor, these tend to have ESR values that are at least 100's of mOhm or add a resistor which is at least 200mOhm in series with your ceramic capacitor.
Another risk is that your capacitor value may be derating significantly when biased, we have an app note that discusses this which you can find more information on here.
