Conformity Magazine - September 2007 - (Page 22)

ESD Open Forum Transient-Induced Latch-Up Test Provided by the ESD Association Q: A: Will testing my device with a Transient-Induced Latch-up (TLU) test help in isolating transient susceptible device designs? The answer is yes! Transient-Induced Latchup testing, using the ANSI/ESD SP5.4-2004 Standard Practice, has been shown to replicate field failures or failures occurring during burn-in testing, that other standard latch-up test methods have not. The ESD Association (ESDA) standard practice ANSI/ ESD SP5.4-2004 outlines testing techniques that may help reproduce in-field failures, which up till now have not been reproducible. The ESDA Transient Induced Latch-Up (TLU) working group (WG5.4) developed the Standard Practice based on information gathered from a number of years of experiments using different device technologies. Different transient stimuli were also evaluated, in an attempt to replicate real world failures. This information is presented in the ESDA TLU Technical Report (ESD TR-5.4-01-00) and can be used as a reference when trying to understand how the Standard Practice was developed and how to implement it. Since the Standard Practice was released, the work group has focused their experiments on using a negative going rectangular pulse as the stimulus. The test requires the device be biased to its nominal Vdd voltage level, the transient pulse generator would then force the Vdd rail negative, holding it there for 20us before returning it to the nominal Vdd voltage. During the time of the pulse, current and voltage measurements on the power supply rail are recorded and used as the basis for determining whether latch-up has occurred. During the event, if there is a sudden and sustained increase in the supply current, then latch-up has occurred. Figure 7, taken from ANSI/ESD SP5.4-2004, shows an idealized representation of how the stress is applied to the Vdd rail, while the voltage and current measurements are being recorded during the event. Figure 8, also taken from Standard Practice shows the results of an actual device test. Idd current being measured on channel 2 of the oscilloscope clearly shows an increase in the current draw, after the negative going transient event has been applied to the Vdd rail. Unlike other latch-up test methods, which force or sink current on an IO pin, or attempt to over-volt the supply rail, possibly 22 CONFORMITY SEPTEMBER 2007 © Photographer: Kiyoshi Takahase Segundo | Agency: Dreamstime.com causing an EOS event, the TLU test method introduces a short duration negative pulse, which reduces the time that the trigger current flows thereby reducing the possibility of EOS damage due to over-current or thermal runaway. The committee has also found that, by using this method, the transient signal is distributed to all parts of the die powered by the supply under test, greatly increasing test coverage to a larger proportion of the device’s structures. The TLU Work Group (TLU5.4) is in the process of writing a second Technical Report (TR) which outlines some of the recent findings during our additional experiments. This report should be available later this year. Equipment manufacturers are now offering systems that will allow designers to test their devices using the Standard Practice, which will also lead to new discoveries and further improvements in the test methods. ■ Q: A: When will the TLU standard practice become a real standard, with specific stress levels and failure criterion? A number of companies have begun to use the method on a wider variety of parts; however, more feedback on the SP’s implementation and actual result data is needed by the ESDA working group. This information can help drive changes to the standard practice, which will also drive the SP towards a Standard Test Method (STM). Please review and implement the Standard Practice and provide feedback on your findings to the ESD Association headquarters. ■ http://Dreamstime.com

Table of Contents Feed for the Digital Edition of Conformity Magazine - September 2007

Contents Editor’s Note FCC Extends Disability Access Requirements to VOIP Commission Fines Importer $3 Million Over Non-Compliant TVs FCC Gets Tough on Retailers Over Analog TV Tuner Labeling Analog Cellular Service Sunset Date Reaffirmed Commission Adopts Recommendations of Katrina Panel Free-Space Antenna Factors Through the Use of Time-Domain Signal Processing Editorial Correction ESD Open Forum An Update on Revisions to IEC 61000-4-2, the Basic Standard on ESD Practical Advice for Meeting the DFS Testing Requirements of the FCC The EMC Impact of Embedded Software ESD Design Buyer's Guide Tate Renominated to the FCC EPA Releases Report on U.S. Electronic Waste Additional Standards For The EU’s Toy Directive Medical Device Manufacturer Enters Consent Order Updated Guidance Document on Laser Products Issued FDA Offers Advice on Defective Heating Pads CPSC Issues China Product Safety Program Report Other CPSC Actions In The News IEC Standards Update Product Reviews Product News UL Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - September 2007

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