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How 0.1uF a Capacitor can eliminate noise in digital VCC ic power pin

Hi,

everybody commonly using 0.1uF capacitor in VCC line of digital Ics for noise elimination. Why not 1uf? Why not 1nF? What is the exact reason behind this 0.1uF usage?

Regards

Aneesh

  • Hello Aneesh,

      You are correct in highlighting that a 0.1uF decoupling cap is not always the definitive solution.  The decoupling capacitor, in conjunction with the device and circuit R and L, creates a low-pass filter to remove noise and transients.  There are some typical R and L values in standard pcb design, so in general, the 0.1uF cap provides a general guideline for common noise and transient conditions.  And, there are cases when other value caps are to be used, or even combination of caps, such as 0.1uF, 1uF and 0.01uF on the same rail.  Keep in mind the type of cap used also can make a difference, so it is not only the value to be considered.

    Here is an App Note that discusses some of this:  www.ti.com/lit/an/scba007a/scba007a.pdf  .

    At your service,

    ~Leonard