Lpc2000

It's not easy and there are only well known general rules. Use emi 
filters on high speed lines where possible (e.g. murata EMIFIL or 
similar), use ground shielding as much as possible. Avoid current 
flowing through shielding / ground planes. Add external shield if 
nothing else works. It's tough task. I had similar issues with smaller 
MCU (x51), which was solved with EMI filters and grounding with 4-layer PCB.

M.

tsvetanusunov wrote:

>
> > Hello,
> >
> >   I am currently in the middle of a design for the 2138. EMI is very
> > important in the design.
> >
> >    Are you used multilayer boards? How about series resistors on all
> > the lines (both input and output)? Do you have a resistor in series
> > with the XTAL2 output? How about 100pF capacitors on all the I/O
> that
> > goes off the board. What crystal frequency are you using? How about
> > ferrites on all level transistion devices (like RS232 and such)?
>
> we use double side board, the problem is not in the crystal
> definitely as if PLL is not enabled this noise is not generated
> IIRC PLL works on 150-180 Mhz and the radio iterference is caused
> probably when PLL frequency pass through 108Mhz FM range
>
> Best regards
> Tsvetan
> ---
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