I don't know what your device looks like -- perhaps it is hand held?
With USB jacks installed in PCBs we find that the shell needs to be tied
to circuit ground. It can also be tied to chassis ground (case ground)
if that is available. Tying the USB shell to chassis only has caused
problems for us.
The standard is fine, we have customer devices tested upwards of 20KV!
The levels are dependent on the market and application. We have also had
troubles with hand-held devices at 6KV. With a hand-held there is
nowhere for the ESD energy to go after discharge, so making sure the
discharge path creates just common mode voltages is critical. Adding
physical protection so that direct contact is not possible helps.
Curt
in real life
Curt McNamara P.E. // principal electrical engineer
Logic Product Development
411 Washington Ave. N. Suite 400
Minneapolis, MN 55401
T // 612.436.5178
F // 612.672.9489
www.logicpd.com
Bharathkumar Raju wrote:
> Dear Memebrs,
> I feel EN61000 - 4 - 2 is an over kill for assessing the ESD
> immunity level of a device. An USB device with a CCD type sensor is
> repeatedly failing in the lab testing conducted as per the standard
> and as per sensor manufacturer's recomendations. On the other hand the
> sensor manufacturer claims that millions of sensors are deployed in
> the field for more than a year and absolutely no field returns on ESD
> account. The lab results are not at all matching with field results
> calimed by the sensor manufacturer. As a product certification
> engineer, I am confused whether to give the go ahead to my company
> for the mass production.
> I look for the members advise
> a. Do you see a reasonable match between the EN 61000 - 4 - 2 lab
> test results and field results.
> b. Is there any other standard that you feel better than EN 61000 - 4 - 2.
>
> Wishing you all a Happy Christmas & Prosperous New Year 2008
>
> Bharath
>
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