[hpsdr] bypass caps

[Ray Anderson]

>-----Original Message-----
>From: hpsdr-bounces at hpsdr.org [mailto:hpsdr-bounces at hpsdr.org] On
Behalf Of >FRANCIS CARCIA
>Sent: Thursday, July 06, 2006 6:12 AM
>To: hpsdr at hpsdr.org
>Subject: [hpsdr] bypass caps

>***** High Performance Software Defined Radio Discussion List *****
>hi All,
>Trace terminations to bypass caps can have a big effect on RF
performance.
>A simple trace to one side of a chip cap adds a lot of inductance in
series >with the cap. The best termination is to use 2 traces to the cap
contact in >and out. The ground side usually goes to a plane but the
high side >termination can degrade the performance of the bypass. frank
wa1gfz


Actually, the preferred method to achieve low mounting inductance for
decaps is to attach the decaps directly to power planes on both the GND
and VCC side. The spreading inductance contributed by the planes is many
times lower than you can ever achieve utilizing traces. The closer the
spacing of the GND and VCC plane pair the lower the inductance. 

For really low mounting inductance you can go to a via-in-pad design or
vias between the pads to connect to the planes. The bottom line is you
want to minimize the current loop area. 

-Ray	WB6TPU




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