Decoupling capacitor

[Murugesh_89]

Hi,

In most of the places i am seeing a 0.1uF capacitor is used for decoupling either in power supply/IC.

What is the reason for the particular value? What happen if i use 0.001uF of 1uF?

 

[HasHx]

1 uF is used as a charge pump, when you have big current consumption.
0.1 uF, 0.01 uF, and 0.001 uF are used for decoupling GND plane from PWR plane, each for a certain noise frequency (tone) that depends on other circuit components that share the same planes.

Ciao!

 

[KlausST]

Hi,

There already were a lot of discussions about "decoupling capacitors" in this forum.
Discussing values, frequency range, dielectric materials...

If you do a search you will find all informations you need.

Klaus

 

[treez]

What happen if i use 0.001uF of 1uF?

Almost certainly those values will be fine too.
100nF is just handy as the rise time isnt too bad..........generally speakign those kind of decouple caps in PSU's are all made the same value and part so that the BOM is minimised......so i would say that is your answer....BOM minimisation.........thinking about it, 1nF may be a bit low for eg providing the agte pulses to a PWM controller gate drive....so yes, 100nF is the minimum value.......generally for a PWM chip a couple of uF's is used for the gate drive though......as the gate pulse is sometimes say 1.5A high even if only for short time.

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it also depends on the trace impedance fromn the main bulk decoupler....if that is high then you need more capacitance....so its obvious in that respct, you just need big enough cap to ensure the pin voltage doesnt get pulled down too much.....i always use 100nF 0603, X7R's on any opamps or comparator chips etc.