To calculate the value for a decoupling capacitor (Vdd pin to Vss), I use the formula(adsbygoogle = window.adsbygoogle || []).push({});

[tex] I=\frac{C \cdot dv}{dt} [/tex]

But what do I do if I don't know the load capacitance?

For example, I have a push/pull comparator whose output is connected directly to an input of a PIC mcu. The capacitance of the input pin is not specified in the PIC's datasheet. I can't accurately calculate the decoupling cap value for the comparator's Vdd pin. What am I supposed to do? Is there another way to go about calculating it with different parameters? I just used missing capacitance as an example but what would I do if the rise time or some other parameter wasn't specified?

Relevant datasheets:

Comparator

MCU

On another note, what do you do when a datasheet gives a recommended value (0.1uF) for a decoupling cap, but if you actually do the math, you get a way different result? Should you stick with the recommendation even though it's likely that the writer just specified a rule-of-thumb value? Like on page 70 of this digital pot

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# Calculating Decoupling Capacitor When Datasheets Don't Specify Parameters

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