As a part of a circuit, I want to power an opamp LM311 with a 5V DC single supply. The whole circuit will be supplied by a 24V DC supply. To avoid another power supply I want to use this 24V to 5V DC-DC converter to power the opamp. I guess this converter doesn't require any heat sink. The opamp will draw around 5mA from this converter. Here is the data-sheet of the converter.
Below is the ripple of 5V output of this converter in AC coupling without loading. The ripple is around 1.7kHz with 40mV peak to peak:
And here below is the ripple in again in AC coupling without loading but this time I used a 1000uF 25V electrolytic capacitor. In this case the ripple is around 80Hz with around 10mV peak to peak:
I used a 1000uF capacitor in parallel with the converter and reduced the ripple as you see above in the scope outputs. But still there is ripple. Is this ripple acceptable? What is the criteria? I mean for a 5V supply is 10mV pk-pk ripple by using the 1000uF cap fine for this application(powering an opamp)? And if I use 5000uF or more I guess the ripple reduces more. But what is the limit here for the capacitor value? Is there a methodology I can summarize as a rule of thumb?