ESD measurements enhance simulations

Researchers at Missouri University can simulate the effects that electrostatic discharge will have on a device.

Martin Rowe, Senior Technical Editor -- Test & Measurement World, 4/14/2011 12:01:38 PM

Design engineers often must add ESD (electrostatic discharge) protection to electronic circuits, and then test engineers or EMC (electromagnetic compatibility) engineers must verify that a discharge won't harm the circuits. Students and faculty at the Missouri University of Science and Technology's EMC lab (Ref. 1) study the effects of ESD and develop models that designers can use to predict performance.

In a recent paper called “Full-Wave Simulation of an ElectroStatic Discharge Generator Discharging in Air-Discharge Mode Into a Product,” graduate student Dazhao Liu and others developed a SPICE model of an air-discharge ESD event (Ref. 2). Their goal was to estimate an arc length based on a rise-time measurement of current discharged into a device. From the arc-length model and the impedance of of the device under test, the researchers can simulate the effects that ESD will have on a device. Those effects include electromagnetic fields produced by the discharge, which can couple into PCB traces and produce damaging currents.

To verify the model, the researchers used a commercial ESD simulator in air-discharge mode to discharge 5 kV into an MP3 player placed in a dielectric sheet above a ground plane. They measured the current from the discharge that entered the MP3 player using a current probe and an oscilloscope. The rise-time measurement went into a SPICE model that's based on the Rompe and Weizel model. It describes an arc as a resistance during the first tens of nanoseconds following a discharge.

Because they knew the impedance of the device under test, the researchers could use the recorded data to simulate the fields that a discharge can generate inside the MP3 player. Those fields can then couple into circuits in the player, producing unwanted current.

References

1. Rowe, Martin, "The EMC continuum," Test & Measurement World, May 2010.

2. Liu, D., A. Nandy, F. Zhou, W. Huang, J. Xiao, B. Seol, J. Lee, J. Fan, and D. Pommerenke, “Full-Wave Simulation of an Electrostatic Discharge Generator Discharging in Air-Discharge Mode Into a Product,” IEEE Transactions on Electromagnetic Compatibility, February 2011, p. 28. ieeexplore.ieee.org.