FreeLists / si-list / [SI-LIST] Re: Strange resets happening in one of our circuit boards

[m.j.farrell@xxxxxxx]

Ken Wyatt of Agilent made a EMC Precompliance Testing and Case Studies 
presentation back in November 17, 2005 at our Denver IEEE EMC chapter .  Ken 
demostrated several simple ESD testing one can perform to produce radiant noise 
like a ziplok bag with coins, a piezoelectric lighter, "Doug Smith's ESD ruler. 
 Plus ESD detector devices and preventive design techniques.
http://www.ewh.ieee.org/r5/denver/rockymountainemc/archive/2005/November/200511_Presentation.htm
http://www.ewh.ieee.org/r5/denver/rockymountainemc/archive/2005/November/Ken_Present.pdf

Mike Farrell


-------------- Original message from "Peterson, James F (FL51)" 
<james.f.peterson@xxxxxxxxxxxxx>: -------------- 


> 
> An observation : 
> It looks like since the reset can be driven from two places (JTAG port 
> and Power monitor), these drivers must be of the open-drain or 
> open-collector sort. This means that when at a logic 1 level they are 
> not driving anything - the only thing keeping it to a logic 1 level is 
> your 1K ohm resistor. This will not take near as much energy to toggle 
> than if it was driven high by some low-Z logic device. 
> 
> regards, 
> Jim 
> 
> 
> 
> -----Original Message----- 
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] 
> On Behalf Of Carlton Ross-ra8188 
> Sent: Friday, June 02, 2006 10:23 AM 
> To: SI-List 
> Subject: [SI-LIST] Re: Strange resets happening in one of our circuit 
> boards 
> 
> Doug Smith tells a classic chair ESD story in his training. I think this 
> is your problem.=3D20 
> 
> The likely case is that ESD from the chair is coupling into your JTAG 
> cable. Since your JTAG cable contains a conductor connected to the micro 
> RESET pin, a susceptibility problem should be no surprise. You may want 
> to try shielding the cable or placing ferrite(s) at the board connector. 
> Alternately, you could provide protection for your RESET pin by 
> implementing an RC low-pass filter at the micro. You can test this by 
> soldering a leaded 100nF capacitor from the RESET pin to the nearest VSS 
> pin.=3D20 
> 
> Ross Carlton 
> Freescale Semi. 
> 
> 
> -----Original Message----- 
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] 
> On Behalf Of Zhangkun 
> Sent: Thursday, June 01, 2006 8:20 PM 
> To: Shiraz.Bashir@xxxxxx; SI-List 
> Subject: [SI-LIST] Re: Strange resets happening in one of our circuit 
> boards 
> 
> Shiraz Bashir 
> 
> Normally, the power ground noise could not be so strong to reset the 
> system. 
> 
> Best Regards 
> 
> Zhangkun 
> 2006.6.2 
> 
> ----- Original Message ----- 
> From: "Bashir, Shiraz (GE Healthcare)" 
> To: "SI-List" 
> Sent: Friday, June 02, 2006 7:42 AM 
> 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. 
> >=3D20 
> > 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 
> >=3D20 
> > OR 
> >=3D20 
> > 2. If we keep solder wires for scoping purposes. 
> >=3D20 
> > It doesn't happen when Unit is enclosed in it's metal housing. 
> >=3D20 
> > 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 
> >=3D20 
> > 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. 
> >=3D20 
> > Fix:=3D3D20 
> > A team member recommended to put a capacitor across resistor. Did that 
> 
> >and problem went away. 
> >=3D20 
> > Can anybody explain why it is happening ? Is it noise from Power 
> Supply 
> > but how can it defeat a strong pull up ? 
> >=3D20 
> > Thanks, 
> > Shiraz Bashir 
> > General Electric Healthcare 
> > ------------------------------------------------------------------ 
> > To unsubscribe from si-list: 
> > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field=20 
> >=3D20 or to administer your membership from a web page, go to: 
> > http://www.freelists.org/webpage/si-list 
> >=3D20 
> > For help: 
> > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field =3D20 =20 
> >List FAQ wiki page is located at: 
> > http://si-list.org/wiki/wiki.pl?Si-List_FAQ 
> >=3D20 
> > List technical documents are available at: 
> > http://www.si-list.org =3D20 
> > List archives are viewable at: =3D20 
> > http://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 
> > =3D20 
> >=3D20 
> >=3D20 
> ------------------------------------------------------------------ 
> 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: 
> http://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: =3D20 
> http://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 
> =3D20 
> 
> ------------------------------------------------------------------ 
> 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: 
> http://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 
> http://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: 
> http://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: 
> http://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:
http://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:     
                http://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