[SI-LIST] Re: Strange resets happening in one of our circuit boards
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: Shiraz.Bashir@xxxxxx
- Date: Thu, 01 Jun 2006 20:30:41 -0400
Shiraz
Sounds like something that Doug would be able to help with.
Scott
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed® is the registered service mark of
Teraspeed Consulting Group LLC
Bashir, Shiraz (GE Healthcare) wrote:
> 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:=20
> 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:
> //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
>
>
>
------------------------------------------------------------------
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:
