[SI-LIST] : Decoupling capacitor resonance

About this list Date view Thread view Subject view Author view

From: Chris Bobek ([email protected])
Date: Tue Jan 25 2000 - 17:42:02 PST


There's been a lot of discussion about selecting the right decoupling
capacitor(s) for an IC. Howard Johnson's philosophy seems to say "pick
the largest value cap(s) in the smallest smt package that you can
reliably purchase". I tend to agree with that. However, I have an
appnote for a PLL (f~=50Mhz) that says to use a 22uF and a 10pF to
properly decouple the device. Instead, I'm using a 22uF and a 0.1uF in
the smallest package I'm allowed to procure (0805). FOR THE SAME SIZE
PACKAGE, should I change the 0.1uF to 10pF? If so, why?

My understanding is that the inductance of the 10pF and 0.1uF is almost
equal (because they are in the same size package). Inductance being
equal, the larger capacitance is better because it provides a lower
impedance to ground. Therefore, using a 10pF would not gain us anything
except an extra part to procure in addition to our ubiquitous 0.1uF's.

Thank you for your help/insight,


**** To unsubscribe from si-list: send e-mail to [email protected] In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu

About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Apr 20 2000 - 11:34:49 PDT