by: cc: (bcc: Wan
Juang Foo/ece/staff/npnet)
owner-emc-pstc@majordo Subject: SV:
Decoupling - capacitor values
mo.ieee.org
04/20/02 03:45 PM
Please respond to
amund
Tim,
The standard is IEC/EN60945:1997, Maritime navigation and radio
communication equipment and systems - General requirements- Methods of
testing and required test results. Almost all ship classification societies
as Lloyd's Register (LR), Germanischer Lloyd (GL), American Bureau of
Shipping
Amund,
You do not HAVE to be in a chamber to keep working on this. Since there is
only one Vcc pin (which processor IS this? - be SURE there is only one Vcc
pin; you may have an unfiltered, unconnected Vcc pin or two) you are
limited in how many capacitors you can attach to it. This doesn't
We spend a few hours in an EMC lab today, trying to suppress the unwanted
162MHz signal. We had to suppress it approximate 5 dB. There existed 100nF
caps on the Vcc pins but the caps lead was long. We went on decoupling
(1nF and 100nF) with short leads (not OMF caps) on the uP Vcc pin and on
Amund,
I have encountered similar problems with similarly designed boards. In one
interesting case, I was able to get 30 dB reduction in radiated EMI by
adding a series resistor to a (fairly short) low-frequency clock line. Due
to use of modern devices, its rise and fall times were less than a
Interesting articles on your web-site, Tim.
BTW, how about just using a 100 pF capacitor with the 'leads' hugging close
to the microprocessor package
There's a mile from the Vcc pin to ground, that's another problem. No
ground plane, only ground traces which is routed around on the PCB. This
Correct, the picture is complex. The PCB is 2-layer with signal, 5V-power
and 0V-ref lines routed on both sides. There is no ground layer/plane. There
must be a large number of RF current loops because the 0V-lines are routed
up and down and around.
Beside trying to achieve a good decoupling I
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