Robert,

three vias help to minimize overall inductance of decoupling caps which
will return improve high frequency decoupling. A method that has less
burden for the layout engineer is to use a very thin core between the
ground and power plane (100um or less) of  the pcb. This is the best
technique to improve high frewuency decoupling. For low an medium
frequencies, use several caps with different values (which means different
frequency response). The values of the caps shouldn't differ by more than a
factor o 100. Use groups of caps with slightly different values e.g.
100nF/2.2nF and 220nF/6.8nF. This will improve decoupling over a broad
frequency range.


Regards,

Peter
-----Ursprüngliche Nachricht-----
Von:    Robert Blake [SMTP:[log in to unmask]]
Gesendet am:    Dienstag, 9. Februar 1999 12:22
An:     [log in to unmask]
Betreff:        [DC] Motorola MC68360 ?

Hi all,

Can anyone out there who has used a ceramic Motorola Processor MC68360 in a
design give me any pointers to a good layout. The data sheets indicate that
decoupling capacitors should have  at least three vias from each capacitor
going down to a GND plane. A total of twenty decoupling capacitors around
the device is recommended. This is the first time I have seen a requirement
for multiple vias. Getting one via in is normally a headache but three. Has
anyone else used this before.

Thanks in advance for any tips.

Regards

Robert (London UK)





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