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'PATENTED EMI REDUCTION TECHNOLOGY WITH PIC 20 pin'
1998\08\20@160429 by WF AUTOMACAO

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Does someone know this kind of PIC IC with EMI Technology?

       Miguel

1998\08\20@170128 by Morgan Olsson

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At 16:57 1998-08-20 -0700, you wrote:
>Does someone know this kind of PIC IC with EMI Technology?
>
>        Miguel
>

Remove power...
Or put in 230VAC for a while, and there will be no more EMI.
Always works :)

Actually,
take care of layout, decoupling, external drivers, anything...

/Morgan
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  spam_OUTmrtTakeThisOuTspaminame.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\08\20@171537 by WF AUTOMACAO

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Morgan Olsson wrote:
>
> At 16:57 1998-08-20 -0700, you wrote:
> >Does someone know this kind of PIC IC with EMI Technology?
> >
> >        Miguel
> >
>
> Remove power...
> Or put in 230VAC for a while, and there will be no more EMI.
> Always works :)
>
> Actually,
> take care of layout, decoupling, external drivers, anything...
>
> /Morgan
> /  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
> \  .....mrtKILLspamspam@spam@iname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /
COP has this technolgy! But i don't know if MICROCHIP for the PIC!

Miguel.

1998\08\20@171948 by Russell McMahon

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If you're serious and desperate look at the ST6.
It s slow and very dumb but has excellent EMI performance.
They also do an app note on crystal / CPU layout for least clock
radiation etc.

{Original Message removed}

1998\08\20@212446 by David VanHorn

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>
>Actually,
>take care of layout, decoupling, external drivers, anything...


BING BING BING  You win a cigar :)

Yes, there are no EMI answers like "low EMI microcontrollers" or "FCC
approved microcontrollers".
You have to lay the board out right. You can make the noisiest chip near
silent, and you can make the quietest chip flunk horribly.

1998\08\20@222807 by Craig Webb

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Somebody gave a URL suggestion yesterday for an EMI reduction app note. Can
you please post it again?

Thanks.

Craig

1998\08\21@121102 by John Payson

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>>Actually,
>>take care of layout, decoupling, external drivers, anything...

>BING BING BING  You win a cigar :)

>Yes, there are no EMI answers like "low EMI microcontrollers" or "FCC
>approved microcontrollers".
>You have to lay the board out right. You can make the noisiest chip near
>silent, and you can make the quietest chip flunk horribly.

I received e-mail once from an engineer at HP who designed a 40MHz microprocessor board for one of HP's printers; the thing was a double-sided (not 4-layer) board, memory-bus speed was 20MHz, and the thing passed FCC without ANY shielding!  Took him quite awhile to get the layout perfect, but when you're making oodles of something even $0.50 worth of shielding can get expensive.

Generally, I suspect that PIC's (especially the internal-clock ones) are going to be fairly EMI-quiet if you do a good job of bypassing the VDD rail at the chip; putting "magic beads" (ferrites) on any signals that go any distance should kill any EMI junk that remains, but probably isn't really necessary.

In fact, I'd say that PIC's by design take a major step toward EMI reduction vs older microprocessors in that they generally don't have any off-chip memory bus.  Since all high-speed signals are kept confined to a very small area there really isn't much that CAN radiate EMI.

The only other point that I'd mention would be that if you're driving shift registers, etc., especially if the signals are traveling any significant distance, you may want to avoid clocking them "as fast as possible" since even a 4MHz PIC may be able to clock out data at up to 1MHz (if ports are laid out nicely), and 1MHz is fast enough that harmonics can pose real EMI problems.  But if you can afford to add a few NOP's in the shift loop, you should be able to reduce EMI easily.

1998\08\21@121717 by David VanHorn

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>I received e-mail once from an engineer at HP who designed a 40MHz
microprocessor board for one of HP's >printers; the thing was a double-sided
(not 4-layer) board, memory-bus speed was 20MHz, and the thing passed >FCC
without ANY shielding!  Took him quite awhile to get the layout perfect, but
when you're making oodles of >something even $0.50 worth of shielding can
get expensive.


Exactly. I use only two layer myself, in plastic enclosures, with switching
power supplies etc. The latest one had a 300uS 19A @32V pulse requirement.


>The only other point that I'd mention would be that if you're driving shift
registers, etc., especially if the signals are >traveling any significant
distance, you may want to avoid clocking them "as fast as possible" since
even a 4MHz >PIC may be able to clock out data at up to 1MHz (if ports are
laid out nicely), and 1MHz is fast enough that >harmonics can pose real EMI
problems.  But if you can afford to add a few NOP's in the shift loop, you
should be >able to reduce EMI easily.


Always a good idea, not to go faster than you really need to.  Clock lines
should have a resistor at the source end, even if you end up placing a zero
ohm there, if you need to slow the edges, you'll be glad for the pad.  I
hear lots of comments about placing CAPS to GROUND on high speed lines,
which is exactly the WRONG thing to do.
You just make the chip draw MORE high frequency current!

1998\08\21@121936 by WF AUTOMACAO

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John Payson wrote:
>
> >>Actually,
> >>take care of layout, decoupling, external drivers, anything...
>
> >BING BING BING  You win a cigar :)
>
> >Yes, there are no EMI answers like "low EMI microcontrollers" or "FCC
> >approved microcontrollers".
> >You have to lay the board out right. You can make the noisiest chip near
> >silent, and you can make the quietest chip flunk horribly.
>
> I received e-mail once from an engineer at HP who designed a 40MHz microproces
sor board for one of HP's printers; the thing was a double-sided (not 4-layer) b
o
>
> Generally, I suspect that PIC's (especially the internal-clock ones) are going
to be fairly EMI-quiet if you do a good job of bypassing the VDD rail at the ch
i
>
> In fact, I'd say that PIC's by design take a major step toward EMI reduction v
s older microprocessors in that they generally don't have any off-chip memory bu
s
>
> The only other point that I'd mention would be that if you're driving shift re
gisters, etc., especially if the signals are traveling any significant distance,

Thanks for this information!

Miguel.

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