RE: [SI-LIST] : Micro Noise

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From: Farrokh Mottahedin (Farrokh.Mottahedin@quantum.com)
Date: Wed Nov 03 1999 - 13:57:53 PST


Is there a "floating" heat sink on your microprocessor? If so, that can be
a significant source of capacively coupled noise.

Regards,

Farrokh Mottahedin

Quantum Corp.
500 McCarthy Blvd.
Milpitas, CA 95035

At 10:31 AM 11/3/99 -0500, you 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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