Thierauf Design & Consulting: Signal Integrity Design, Analysis & Training

Here's the running list of commonly asked questions regarding the new Power Integrity Lab manual. Contact me here if you have questions or would like more information.

  • How is decoupling explained?
    • The book first looks at decoupling in the time domain (the “supplying charge” point of view) and then in the frequency domain (the “PDN target impedance” approach).
  • How is decoupling in the time domain demonstrated?
    • The experiments you’ll perform will show you that poor decoupling can change an IC’s timing, alter a signal’s waveshape, and can cause runt pulses to occur. You’ll use a small homemade ferrite to create current probe; these experiments are really neat because you’ll see the relative magnitudes of the current provided by the DCAPs and the power supply when an IC switches, and you’ll see how adding DCAPs change that.
  • How is decoupling in the frequency domain explained?
    • The book discusses signal and power supply harmonics and target impedance in some detail and shows how adding DCAP can change the PDN's impedance and suppress high frequency harmonics but also sometimes makes high frequency noise worse. You'll use your homemade current probe to measure the harmonics in a signal and in the power feeding an IC. DCAP ESL and resonance (including the important topic of multiple resonances) are also discussed and measured in the lab.
  • Is DCAP resonance covered?
    • Yes, you’ll learn how to use an oscilloscope or a homemade RF voltmeter to measure DCAP resonance. As part of this you’ll see how interconnect inductance and capacitance effect the frequency and shape of the DCAP’s resonance curve.
  • Who is this manual written for?
    • Students and degreed electrical engineers and computer engineers and electronics technicians wishing to learn the basics of power integrity in electronic systems by performing practical, low cost and straightforward hands-on experiments with inexpensive CMOS IC’s.
  • How is the book arranged?
    • The chapters come in pairs: A chapter presenting theory is followed by a chapter of experiments demonstrating that material.
    • Chapters 1 (theory) and 2 (experiments) briefly cover the characteristics of CMOS I/O so you’ll understand why power problems can lead to signal integrity problems.
    • Chapters 3 and 4 cover decoupling and DCAPs theory and experiments in the time domain.
    • Chapters 5 and 6 discuss decoupling, DCAPs and PDN impedance theory and experiments in the frequency domain.
    • Appendix A and Appendix B provide detailed build notes for the projects, including instructions for building and testing the RF voltmeter and AC current probes.
    • Appendix C is a review of decibels. This chapter is supplemental: Decibels only appear in a few places in the manual and this material is included to assist those readers unfamiliar with them.
    • Appendix D is a list of recommended parts (suggested vendor part numbers).
  • What will I need to perform the experiments?
    • A solderless breadboard.
    • A handful of resistors, capacitors, a ferrite or two, a few low-cost IC’s and some test leads. None of the parts are rare, and all are readily available.
  • What test gear will I need?
    • An adjustable power supply (although some of the experiments require a second supply or a 9V battery).
    • A DMM (it’s a bonus if your DMM can measure capacitance).
    • A 200MHz bandwidth dual channel oscilloscope. You can get away with a 100MHz scope, but your results won’t closely match the results in the manual. A sub-100MHz scope is OK for a few of the experiments, but in general low bandwidth scopes won’t work well. It’s a plus (but not a necessity) if your scope can perform an FFT.
    • A function generator that outputs a square wave up to around 5MHz and a sine wave up to about 15MHz. You still can perform some of the experiments even if your generator dosn't go up that high. It’s not necessary for it to have a sweep function.
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