Numerical modeling of electrostatic discharge generators

The discharge current and the transient fields of an electrostatic discharge (ESD) generator in the contact mode are numerically simulated using the finite-difference time-domain method. At first the static field is established. Then the conductivity of the relay contact is changed, which initiates the discharge process. The simulated data are used to study the effect of design choices on the current and fields. They are compared to measured field and current data using a multidecade broadband field and current sensors. The model allows accurate prediction of the fields and currents of ESD generators, thus it can be used to evaluate different design choices.     

Characterization of human Metal ESD reference discharge event and correlation of generator parameters to failure levels-part I: reference event

Electrostatic discharge (ESD) generators are used for testing the robustness of electronics toward ESD. Most generators are built in accordance with the IEC 61000-4-2 specifications. Using only a few parameters, this standard specifies the peak current, the rise time and the falling edge. Lacking a transient field specification, test results vary depending on which generator is used, even if the currents are quite similar. Such a specification is needed to improve the test repeatability. As for the current, the specification should be based on a reference human metal ESD event. While keeping the presently set peak current and rise time values, such a reference ESD (5 kV, 850-/spl mu/m arc length) is identified and specifications for current derivative, fields, and induced voltages are derived. The reference event parameters are compared to typical ESD generators.     

A new test setup and method for the calibration of current clamps

Current probes are widely used to measure the common mode currents in electromagnetic compatibility (EMC) applications. Often, it is necessary to characterize the ratio of measured voltage to the common mode currents up to gigahertz (GHz) frequencies. Existing calibration methods for current probes suffer from the problem of not directly measuring the current within the current clamp. Instead they either reconstruct the current from measurements at other locations or they use assumptions regarding the geometry which allows them to use a current that is measured at a different location without applying a mathematical correction. For example, by maintaining a 50-/spl Omega/ transmission-line impedance the current can be determined with low uncertainty. The proposed method overcomes these disadvantages by directly measuring the current at the center of the current clamp. This way the mechanical dimensions of the test setup are not critical any more, i.e., one setup can be easily used to measure a large variety of clamps. The method is primarily applicable for current monitoring probes in the frequency domain.     

Preliminary results on reflectance feedback control ofphotocoagulation in vivo

The size of therapeutic laser-induced retinal lesions is critical for effective treatment and minimal complications. Due to tissue variability, the size of a lesion that results from a given set of laser irradiation parameters cannot be predicted. Real time feedback control of lesion size is implemented based on two-dimensional reflectance images acquired during irradiation. Preliminary results of feedback controlled lesions formed in pigmented rabbits demonstrate an ability to produce uniform lesions despite variations in tissue absorption or changes in laser power     

Characterization of human metal ESD reference discharge event and correlation of generator parameters to failure levels-part II: correlation of generator parameters to failure levels

Most electrostatic discharge (ESD) generators are built in accordance with the IEC 61000-4-2 specifications. It is shown, that the voltage induced in a small loop correlates with the failure level observed in an ESD failure test on the systems comprised of fast CMOS devices, while rise time and derivative of the discharge current did not correlate well. The electric parameters of typical ESD generators and ESD generators that have been modified to reflect the current and field parameters of the human metal reference event are compared and the effect on the failure level of fast CMOS electronics is investigated. The consequences of aligning an ESD standard with the suggestions of the first paper, of this two-paper series, are discussed with respect to reproducibility and test severity.