Slammers And Software Verify Performance Of Advanced Voltage Regulators 
 by David Baretich, ProGrAnalog, Portland, Oreg.
      Digital integrated circuits (ICs) continue to increase rapidly in capability and application. Much of this improvement is due to new processing technology, including smaller feature size, larger transistor count and larger die sizes. With these trends come higher supply current and current step loads, simultaneously with lower voltages and tighter regulation tolerances.
      In turn, voltage regulators must meet these increasingly stringent supply requirements. Peak load currents of several hundred amperes are common, and transient load steps can be a high percentage of full load current. Test equipment designed to exercise and verify these regulators has previously existed only in the realm of custom testers for vendor-specific ICs. In this article we look at the utilization of load slammers, a class of off- the-shelf voltage regulator test devices from ProGrAnalog—and sometimes constructed by engineers for in- house use—as a test utility for high-performance transient load testing.
      We begin by discussing the differences between load slammer measurements versus simulation results, and how load slammers compare with Bode and impedance analyzers in terms of their respective measurement capabilities.
      Mainly the focus here will be on how we configure the LoadSlammer’s GUI to perform a variety of transient, pulse train and impedance tests. Example test results are presented and analyzed with attention given to the various features of the GUI that aid our analysis.The ability of the LoadSlammer to perform dc load testing and the delay feature are also briefly discussed.
      Finally, we note the various benefits in product design and manufacturing that can be obtained by using the LoadSlammer in combination with test suites.

Reaping The Benefits
      Besides simply being able to test voltage regulator performance per a specification, there are additional ways to benefit from using LoadSlammers with a suite of tests. They enable reduced development and debugging time from automated testing. They also permit faster optimization, enabling smaller output filtering, saving cost and board space.
     Meanwhile, testing is made easier with the ability to generate documentation over a wide range of electrical and environmental conditions for a more-robust design. Similarly, LoadSlammers with test suites support manufacturing testing to verify and document performance of individual boards and fixtures for future reference, increasing production yield. Designers can also verify board performance over time as components degrade, and use the test suites to debug field returns.
    Finally, it’s possible to reduce the heat and power consumption by using the LoadSlammer to improve transient response of the regulator. A tighter responding regulator can potentially be used to implement dynamic voltage  scaling or other voltage-reduction methodologies.
    Overall, fast transient load testers provide unique, large-signal testing capabilities for qualifying high performance board-level power converters. This capability can yield multiple reliability, cost, and time benefits for boards and systems.

About The Author
David Baretich is an electrical engineer and consultant to ProGrAnalog. He has 42 years’experience in power conversion, working at companies such as Texas Instruments,MicroPlanet, onsemi, Tektronix and Biamp Systems. An IEEE member, David holds 10U.S. patents. He received a BSEE from Iowa State University.For more information on the subject of transient response and transient load testing, see How2Power’s Design Guide, locate the Design Area category and select Transient Response.