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ESD test -- Using a 2KV Mosquito bat as ESD gun?

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player80

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Hi,

today I went to a lab for testing the EMC.
When doing the ESD test my device started to fail (the sensor IC started to reset).

After I went home I started to think about why the IC was resetting and how to reproduce it, suddenly a mosquito bat came into my mind.
I have checked the spec of the bat and it says 2KV, 0.7w

I was able to reproduce the ESD test with it, and fix it by adding a 100nF to the reset line (RST is connected to the MCU with a 300ohm resistor in series and 4.7k to 3.3v). Now the bat is just sparking on the device and everything works fine.

Are those mosquito bats really suitable for such ESD gun tests? I have seen there are even mosquito bats with 4kV available.

We will do another lab test next week with the real ESD gun I'm curious about the new results.
 

I think mosquito bats are great. For mosquitoes. Obviously you were able to solve your problem with it, but it's not really lab-quality test equipment. You would be hard-pressed to justify ESD compliance.
 

In a pinch, I have also used flint-less gas lighters as quick and dirty ESD guns (with the gas tank fully empty, of course).

But as Barry has accurately mentioned, you cannot validate or assure ESD compliance with an un-calibrated equipment with unknown energy levels, unknown waveform shapes and most likely, poor repeatability.
 

ESD testing, to be meaningful beyond "yep, blowed up
real good!", has to be traceable to a common standard
in the electrical details. There are only a few "models"
(old HBM, CDM, MM and some newer ones I don't know
details, of). Key are source resistance, source capacitance
and source voltage. Depending on how the waveform is
generated / applied you might also care about standard-
compliant risetimes.

A transmission line pulser is fairly easy and low cost to
build, aside from the power supply. 50-100' of 50-ohm
coax, mercury relay, high value charging resistor, low
value series resistor (for rough output Zmatch). This
can let you capture pin current/voltage waveforms at
ESD-realistic currents (everybody talks about voltage,
but current loop is key) if you want to do things like
characterize your ESD protection elements to enable
explicit design (often we are only provided rules of
thumb, by people who know nothing about ESD or
circuit design, and often are not even provided ESD
protection element models that actually -work- (MOS
device breakdown being kind of a forgotten feature
of older compact models, and modeling group being
more interested in forward-active circuit simulation
accuracy than any "abnormal conditions").

Measuring a few-kV waveform is not going to be easy
or cheap, and accuracy will be kind of on you to assess.
But low voltage ICs can be tested current-mode with
no real issues (at least for HBM where the kV and kOhms
make the threat look pretty much like a pulsed current
source).
 

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