Re: [SI-LIST] : Micro Noise

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From: Adrian Shiner (adrian.shiner@virgin.net)
Date: Wed Nov 03 1999 - 10:24:21 PST


I had the same problem with a display driver. Bite the bullet & screen the
damned thing. Check out the power supply lines.....

If you are in the European Union, it is high time we statred putting some
pressure on the chip manufacturers to get this sort of poor performance
under control. They are arguably in contravention of the EMC Directive. The
internal chip switching rise & fall times are unnecessarily short in many
(most??) cases & users pay the price to stop the EM problems.

Adrian

----- Original Message -----
From: <Lfresearch@aol.com>
To: <si-list@silab.eng.sun.com>
Sent: 03 November 1999 15:31
Subject: [SI-LIST] : Micro Noise

> 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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