Re: [SI-LIST] : Micro Noise

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From: Ron Miller (rmiller@Brocade.COM)
Date: Wed Nov 03 1999 - 10:02:47 PST


Derek

If you have the option to add inductance in the power and ground connections to the chip
this will slow up the edges and reduce emi. With a 50 Mhz signal it looks like the
edges could be slowed quite a bit without effecting performance. Good luck.

Ron Miller

Lfresearch@aol.com wrote:

> Hi all,
>
> I have a problem with a microprocessor which appears to be radiating very
> strongly from the package. I've deactivated all other circuits ( pulled
> crystals, pins etc ) on the board. Additionally, the micro is held in reset,
> PROM's are pulled, but it's a noisy as heck. Close field probes ( both E and
> H field ) show the package to be the dominent source of radiation.
>
> The device has a maximum clock rate of 50 MHz, this is where we're using it.
> Clock it at 32 MHz and the emissions fall about 10 dB up to about 300 MHz,
> more above 300 MHz. Yes it's a CMOS device.......
>
> Am I stuck with putting a can over the chip? The product has a plastic
> package, so there is no shielding available at all.....
>
> Thanks,
>
> Derek
>
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Ronald B. Miller  _\\|//_  Signal Integrity Engineer
(408)487-8017    (' 0-0 ') fax(408)487-8017
     ==========0000-(_)0000===========
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