From: Chris Rokusek ([email protected])
Date: Wed Nov 03 1999 - 09:20:48 PST
You may also want to rule out noise induced from said IC onto the VDD/GND
network by taking a conducted V(f) measurement across the VDD/GND at IC
location. This noise results primarily from "shoot-through" currents of the
CMOS drivers and can be reduced by improving power bus decoupling.
Also, of course large near fields don't ALWAYS translate to large far
If you can replace uP with equivalent from another MFG and radiation goes
down then cause is likely power/gnd routing on the die so you can try to
pass the buck to IC MFG.
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of [email protected]
> Sent: Wednesday, November 03, 1999 7:31 AM
> To: [email protected]
> 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.....
> **** To unsubscribe from si-list: send e-mail to
> [email protected] In the BODY of message put:
> UNSUBSCRIBE si-list, for more help, put HELP. si-list archives
> are accessible at http://www.qsl.net/wb6tpu/si-list ****
**** To unsubscribe from si-list: send e-mail to [email protected] In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****
This archive was generated by hypermail 2b29 : Tue Feb 29 2000 - 11:39:33 PST