[SI-LIST] Re: Strange resets happening in one of our circuit boards
- From: "Chris Cheng" <Chris.Cheng@xxxxxxxxxxxx>
- To: "SI-List" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 1 Jun 2006 17:05:46 -0700
I really don't know how to fix your problem but can you please tell me =
what hospitals use those eqipments ?
TIA
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Bashir, Shiraz (GE
Healthcare)
Sent: Thursday, June 01, 2006 4:42 PM
To: SI-List
Subject: [SI-LIST] Strange resets happening in one of our circuit boards
Hi,
A unit with microprocessor based system circuit board is resetting when
we plug in emulator port in JTAG port.
Using scope we see that CPU reset pin is asserted, hence the reset.
We see +5/-3V worth of noise on the signal just by rolling my chair back
and forth in front of the emulator.
This happens in following scenario:
1. User is sitting on chair, user gets up (doesn't touches the
unit) and unit resets.
We demonstrated this on three randomly selected units.
Sounds ridiculous but it is true
OR
2. If we keep solder wires for scoping purposes.
It doesn't happen when Unit is enclosed in it's metal housing.
Investigated..
a. Reviewed schematics and CPU's reset line is pulled to 3.3V using 1K
ohm resistor.
b. Physically checked that pull up resistor is in place and is connected
with BGA ball of reset pin.
c. We checked power monitor chip which can drive reset too..but no issue
there.
D. Reset line is not going anywhere else other than JTAG port and Power
Monitor Chip
Brainstormed..
a. Soldering issue due to BGA ? Ruled out as how can soldering issue be
on three randomly selected units.
b. ESD- Ruled out as per our understanding ESD (air discharge) cannot
"arc over" from 2-3 feet distance.
Fix:=3D20
A team member recommended to put a capacitor across resistor. Did that
and problem went away.
Can anybody explain why it is happening ? Is it noise from Power Supply
but how can it defeat a strong pull up ?
Thanks,
Shiraz Bashir
General Electric Healthcare
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at: =20
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
=20
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
