[SI-LIST] Re: ESD failure - need advise

  • From: Douglas Smith <doug@xxxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Tue, 23 Sep 2014 23:53:40 -0700

 Hi Ramesh,
I agree with Steve Weir, if you knew enough to simulate the problem
accurately you would already be able to fix it without the simulation. The
physical implementation of the system is at least important as the schematic
as the parameters that affect ESD performance are usually parasitic
capacitance and inductance on the order of a few pf or nh.

I find mapping out ESD current paths through measurements or injecting
controlled amount of ESD like noise (not necessarily from an ESD simulator
but inductively from a pulse generator with a large di/dt output) to be
useful. The Fischer Custom Communications TG-EFT pulse generator is one of
myfavorite for the purpose. You can contact me privately for more
informationif you like.

On 9/23/14 4:20 PM, steve weir wrote:
CM ESD energy is converting to DM noise. Your flex cable should be an
immediate suspect. That said, you could suffer from any of the many ills
thatDoug Smith regularly writes about. Going after the problem with software
now that the product has already been designed is probably not a very
productive approach. Software is a good way to test ideas and assess risk
while you are still making design decisions. If you go the software route
now, it will after you learn to use it and get your models set-up properly
tell you what you already know: Your design fails. Steve. On 9/23/2014 3:48
PM, Ramesh N wrote: Hello Experts, Greetings!!! we are having ESD fail (in
regulatory testing) in one of our design. It's simple wireless DAQ system
with 2 boards [controller PCB + LED/Sensor PCB]. FPC cable (5") is used as
interconnect.Package is abs plastics. Light-pipe is used for the for led
indication. When +8kV is applied through air discharging, inadvertent LED
trigger occurs . Randomly, system is also hanging when multiple zapping
applied (especially for 8kV voltage level). I have tried to limit airgaps,
added filter caps, etc but issue is not entirely solved. Is there any ESD
simulation/analysis tool available for addressing this failure analysis? Any
help/debug tips related to this would be very helpful. Thanks and regards,
Ramesh ------------------------------------------------------------------ To
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