From: Yehuda D. Yizraeli ([email protected])
Date: Wed Nov 03 1999 - 20:20:28 PST
Hi All,
Just to add something we just found out good to think of: Does scan make
chips to fail, does it test the chip at all, is it under-test or over-test,
how can we correlate test conditions to real life operation mode. We would
like to do it faster, but design the chips with minimal power supplies
width. I think this is very important topic and would like to hear ANY data
on it.
regards, yehuda
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of [email protected]
Sent: Wednesday, November 03, 1999 6:19 PM
To: [email protected]
Subject: Re: [SI-LIST] : Micro Noise
A few thoughts, not necessarily connected.
Many times self-test operations generate more power supply transients than
actual operation. Is there decoupling explicitly on the chip or the
package? If you allow the part to start operating on a very low activity
code loop, does it generate a stronger or weaker near field?
Are all of the off-chip drivers tristated during reset or are they toggling
or static?
If the crystal is pulled, what is generating the clock to the device?
Something internal to the chip? What frequency does it operate at without
external guidance?
Joe
CEC Analysis and I/O Design
Phone: 507.253.0762 Fax: 507.253.4966
[email protected]
[email protected] on 11/03/99 09:31:26 AM
Please respond to [email protected]
To: [email protected]
cc:
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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