In message <002301d0f04a$32a7faa0$97f7efe0$@westin-emission.no>, dated
Wed, 16 Sep 2015, Amund Westin <am...@westin-emission.no> writes:
I have a 450MHz spurious. Only 2 dB margin to limit EN55022 B.
Can see some potential loops on the PCB and will try to reduce the loop
area.
Or break the loops.
Using only 100nF as decouling caps (size 0603). If introducing a 100pF,
it decrease 450MHz by 6-7 dB. But adding different caps values may
introduce anti-resonant effects and other frequencies may increase.
What happens with smaller values? And 0402 is better for low inductance
I will have to do more investigations, but I will anyway add footprints
for additional caps close into the chip.
Any good / bad experience by adding different cap values for
decoupling?
When trying to 'fix' an existing PCB layout, you get good and bad
results because you can't change many things. This is a major reason why
EMC must be fully taken into account at the design stage.
I may also add more caps footprints spread on the pcb, as often
recommended in the literature. Any experience about spreading caps out
the on pcb?
In general, don't spread out parallel capacitors because the trace
inductances increase the probability of resonances.
--
OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk
When I turn my back on the sun, it's to look for a rainbow
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
-
----------------------------------------------------------------
This message is from the IEEE Product Safety Engineering Society emc-pstc discussion
list. To post a message to the list, send your e-mail to <emc-p...@ieee.org>
All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html
Attachments are not permitted but the IEEE PSES Online Communities site at
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used
formats), large files, etc.
Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html
For help, send mail to the list administrators:
Scott Douglas <sdoug...@ieee.org>
Mike Cantwell <mcantw...@ieee.org>
For policy questions, send mail to:
Jim Bacher: <j.bac...@ieee.org>
David Heald: <dhe...@gmail.com>
