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ESD testing

Hi,

I have been assigned to do some "switching power" ESD testing recently. I a m a beginner engineer. So, please forgive me and do not be offended, if I a sk dumb beginner's questions.

I am using the following setup to test the supplies

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Questions:

  1. I found that that VCP is grounded to Ground Reference plane (GRP) via tw o resistors of value 470Kohm in series. Why 470k and two of them?

  1. The ESD gun air discharge looks like the following ( Human Body Model)

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How can I calculate how much charge this waveform has delivered? Plus if I charge the VCP and HCP plane with this waveform then how can I calculate th e " Electric" and " Magnetic field" generated by this waveform.

I found the following device to measure the electric field of HBM

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But sure that this probe can work for this purpose.

  1. How can I measure input and output impedance of a fly back transformer b ased switching power supply? I found the following paper
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I was unable to understand the whole paper but I think that a separate devi ce is required to measure the input and output impedance of the supply? Is it possible that I can buy one?

mel

Reply to
walravenmelissa
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The charge (Q) of the waveform shown can be estimated by calculating the area of the curve. I estimated 20nC. I cannot say how much is actually delivered to your object of interest.

The usual method, I think, is to measure the input voltage and input current for various load and line conditions, then calculate the impedance. Output impedance is done essentially the same way so measure the output voltage and current at the same time.

A spread sheet will give you the answers. Or you can bang them out manually.

Reply to
John S

Your links are too non-specific (which image, in each case?) to identify, characterize or otherwise illustrate your issue.

ESD testing isn't dependent solely on output impedance, but on the combined, coordinated output node's inherent ot built-in transient immunity. Transient immunity often depends on nonlinear or surge characteristics of parts which play no part in linearly-controlled or passive impedances.

You might, from inspection, get a pretty good idea if transient immunity was a consideration in the design and construction of the DUT. In any event, its expected immunity level should be spelled out clearly in its data or spec sheet. Testing outside of the DUT's designed immunity levels is not going to be a constructive exercise.

I suggest you refer to the relevent standard and accompanying test method that is recommended for the standard. Issues can be referred to specific chapter and verse, when they arise.

RL

Reply to
legg

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