[SI-LIST] AW: Re: ESD on center pin of 6VDC jack input.
- From: "Pommerenke, David" <davidjp@xxxxxxx>
- To: <Ken.Cantrell@xxxxxxxxxxxxxxxx>, <Chandan.M@xxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 19 Dec 2007 11:16:02 -0600
Group,
Judging if testing a connector with an ESD simulator is needed requires =
detailed knowledge on the port's location and use model. The amended IEC =
61000-4-2 explains quite well when PIN testing is required.
However, if a cable is plugged into a connector and a very severe metal =
to metal discharge can occur. This type of discharge (named =93Cable =
Discharge Event=94) is not the reference event for the IEC 61000-4-2, =
the standard is based on the discharge of a human via a small piece of =
metal like a key (=93human-metal ESD=94).
If a portable EUT fails (soft- or hard-error) the moment a cable is =
plugged into a connector I would strongly suggest analyzing the root =
cause of the problem. For portable equipment CDE events will be quite =
likely. In most cases I would discourage adding rubber caps or alike to =
avoid testing this test points.=20
Using a transmission line pulser as injection device models CDE quite =
well, but an IEC 61000-4-2 generator will give you an indication of the =
robustness, at least for soft-errors.
There are many ways to solve such problems, filtering, re-routing, =
software. But all solutions need an understanding where to apply them. =
This requires understanding the root cause: hich net is affected and =
which IC will be disturbed. In our research we use local scanning for =
locating sensitive areas on PCBs or in ICs. Details of the method are =
explained in:=20
Finding the root cause of an ESD upset event
Pommerenke, D; Jayong Koo, Giorigi Muchadze
DesignCom 2006, Santa Clara, Feb. 2006
http://web.mst.edu/~davidjp/publications.html
or
http://web.umr.edu/~davidjp/publications.html
Regards,
David Pommerenke
EMC laboratory, University Missouri Rolla (soon: Missouri Science and =
Technology MST)
573 308 2019 / 573 341 4531=20
-----Urspr=FCngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx im Auftrag von Ken Cantrell
Gesendet: Mi 12/19/2007 9:17
An: Chandan.M@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Re: ESD on center pin of 6VDC jack input.
=20
Chandan,
First I would reference the IEC spec for the specific rules. You want =
IEC
61000-4-2. Your answers will be in there. If the DC jack is not
accesible in normal use, then the area only needs to be swept with the
indirect discharge head. Your definition of "not accesible during =
normal
use" has to be the same as the spec. As I remember, if you recess the =
jack
an quarter of an inch to half an inch, you don't have to do direct =
contact
discharge, i.e., can you fit a finger in there. You can also put a =
"door"
(rubber housing) over the input. There are many ways to make it work.
There are two categories of devices for protecting your equipment =
downline
from the discharge, TVS's(transient voltage suppressor)also called
transorbs, and C/pi filters. The first is a fast triggering shunt to =
ground,
and the second is a low-pass filter that provides dB's of attenuation.
Power supplies typically use filters, I/O lines use transorbs(low shunt
capacitance).
The link below was the first hit on a Google search for transient =
voltage
suppressor.
http://www.microsemi.com/micnotes/125.pdf
Hope this helps,
Ken
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Chandan M
Sent: Wednesday, December 19, 2007 6:48 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] ESD on center pin of 6VDC jack input.
Hi,
We are developing a handheld equipment, which can work on both battery =
and
AC/DC adapter.
AC/DC adapter is not mandatory to be connected while using the =
equipment.
Also there is no connection between the equipment and the earth while
operating on battery.
The DC jack is not accessible in normal use. where as it is accessible
with IEC test finger.
What I am wondering is, should we do contact discharge on the center pin
of the DC jack? And if we need not, I want to know the reason why we =
need
not?
I will be grateful if any can give some info on that.
Regards,
Chandan.
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