Is there a nice rule/formula for this or do we always need to go off of the datasheet? I read today (in a datasheet, no less) that the capacitance should be customized for a given application (no further explanation provided), and I was also told that added caps are not required if the input voltage is stable.
Electronic – What capacitance should be added over the inputs and outputs of a voltage regulator
voltage-regulator
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Best Answer
There are basically 2 types of capacitors around a voltage regulator:
It is also good to notice that a single big electrolytic capacitor cannot replace the smaller capacitor from the datasheet (unless the datasheet states otherwise). The smaller capacitors have a much better high frequency response than the ecap and therefore you want them both.
Beware not to make output capacity too large: Most regulators don't like it when output voltage (due to a charged output capacitor) is higher than its input voltage (due to a switched off transformer). Some datasheets do mention a maximum output capacitance. This is why you sometimes see a reversed diode across the regulators in and output pins.