On Wed, 26 Jul 2000, Dan Michaels wrote:

> >At 07:55 AM 7/25/00 -0700, Brian Aase wrote:
> .......
> >>I want to stay away from the MAX232 et al because they
> >>all contain an oscillator that adds to the overall EMC
> >>noise.
> .......
>
   Max 232 family can be supplied from +5V and other +/- source if
connections to oscilators are interrupted. Without oscillator load the EMC
noise must
be lower than usual. All the problem may occure is to not overload the
comunication pins, the chip will become hot...
   Vasile

>
> Regarding EMI generated by these chips, I have not specifically
> checked the MAX232, but have extensively used the 766x-type
> negative voltage converter chips. Both use similar switched
> capacitor charge pumps. The 766x generate significant EMI - probably
> much more than the MAX232 since they pump more current - but
> if you use a ground plane under the chip, most of the noise
> is squelched.
>
> These facts - re EMI - are not well publicized in the datasheets
> AFAICT. I found this out the hard way by using a 766x [originally
> with no gnd plane] to drive a high sensistivity amp that was located
> 1" away.
>
> best regards,
> - Dan Michaels
> Oricom Technologies
> http://www.sni.net/~oricom
> ==========================
>
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