Editor's Note: In 2007, we published a four-part series on bypass capacitors and decoupling that was very popular with the design audience (links below). Now, one of the authors of Part 4, Kendall Castor-Perry, extends the series with six more sections which explore interactions between supply and capacitor, capacitor materials, and simulation models. This very practical extension blends theory and measurements, and its lessons not only will improve your knowledge but help you minimize problems, some of which can be very subtle and difficult to diagnose and solve.
For various reasons, they are presented to you as linked pdf files, one per week, with the corresponding section links added in successive weeks.
And a big "congratulations" to you if you have gone through all five preceding sections of Part 5 (and any of Parts 1 through 4); you are on the last lap. You've invested a lot of time that will hopefully have a big payback!:
Part 5.1: "The regulators interaction with capacitors": The interaction between the power-supply regulator and the decoupling (bypass) capacitor is explained. In addition, the overall impedance seen by the IC, including capacitors, PCB traces, and voltage regulator is assessed; click here
Part 5.2: "Ring the changes, change the rings": Ringing and other voltage transient effects examined with a small test-current step, as well as effect of capacitor dielectric, click here
Part 5.3: "Some gain, some pain": How coupling affects, and bleeds through, to op amp output; click here
Part 5.4: "Don't get into a macromuddle": Inaccurate op-amp simulation macromodels can lead to misleading results on the effect of bypass capacitors in decoupling applications, click here
Part 5.5: "When Harry regulator met Sally op amp": Examine the signal chain from op amp to load, and the interaction of load current, power supply, and amplifier output, click here
Part 5.6: "Steering in the right direction": Validated simulations and macromodels provide an approach to proper selection of bypass decoupling capacitors in op-amp and other circuits, click here
You can read the previous parts by clicking on the corresponding link:
Part 1: "Choosing and Using Bypass Capacitors," click here
Part 2: "Choosing and Using Bypass Capacitors," click here
Part 3: "Choosing and Using Bypass Capacitors,"click here
Part 4: "Know the sometimes-surprising interactions in modelling a capacitor-bypass network," click
About the author Kendall Castor-Perry has been practicing the electronic arts for over three decades, having designed industrial instrumentation, communications systems and audio circuits. He spends much of his time helping people to solve complex signal-path problems with both empathy and rigor.
When your homeís deep freezer, full of food, experiences an AC power failure while you are out for an extended time, its contents can thaw out. If the AC power is then restored before you return home, the contents can re-freeze and you may never know that your food is spoiled. This has given rise over the years to a number of freezer-alarm circuits and methods to detect thaw and re-freeze.
It seems like we just had LTE and LTE Advanced beginning deployment in base stations everywhere. In spite of that effort, there has been heavy discussion of early development ideas of the 5G next-gen architecture to meet the ever-growing demands of the cellular airwave capacity, speed and customer future needs.
If you have worked in the semiconductor industry for more than a few years I am sure you have heard senior leadership speak about the need for your integrated circuit designs to be first pass successes and not the typical two to three spins or more to reach the targeted performance. The question is this: Is first pass success feasible and should be expected? I do not want to stir up a hornets nest with my response but the answer to the question is that it depends. Depends on what you say? Well, the answer depends on several different interwoven complexities that can determine if first pass success is possible. I would like to explore some possible ways to answer this question. Furthermore, the complexity of this question increases when developing complex mixed signal ICís.
Fortunately for circuit designers, a new tool is available that can simplify the process of identifying the ESD suppression device best suited to an application, which makes it far easier to incorporate circuit protection earlier in the board planning process. The Littelfuse iDesignô Online Simulation and Product Selection Tool
. I received a very good reader question from my last blog post regarding the various parameters that are reported by the tool. Letís take a look at an example and explore the parameters that are returned. In this example we will look at the AD9643-250.