Design007 Magazine

PCBD-Apr2015

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April 2015 • The PCB Design Magazine 61 Important Points to Remember • The dynamic characteristics of the cur- rent sink or load determine the effective area in which the capacitance of the PCB can be uti- lized. • In the case where the PCB is much larger than the calculated effective area, high dielectric materials are of minimal impact in noise volt- age suppression. Better performance is achieved by increasing capacitance either by minimizing power plane spacing, or by increasing the num- ber of plane pairs attached to the current sink. • In the case where the PCB is larger than the calculated effective area, further increases in plane area outside of the effective radius/area also have minimal impact on performance. • In the case where the PCB is smaller than the calculated effective area; increasing the ca- pacitance by using higher dielectric constant materials can improve noise voltage perfor- mance. However, similar, if not better results are achieved by decreasing the spacing or add- ing additional plane pairs. • Decreasing the plane pair spacing not only increases the capacitance but also decreases the inductance of the structure. • The PCB is only one part of a PDN. The VRM, discrete decoupling capacitors, chip pack- age, and on-die capacitance are also very im- portant in achieving the desired performance. PCBDESIGN References 1. Right the First Time, A Practical Hand- book on High-Speed PCB and System Design, Volume 2, by Lee W. Ritchey. 2. Electromagnetic Compatibility Engineer- ing, by Henry W. Ott. 3. Signal Integrity: Simplified, by Eric Boga- tin. article EFFECTIvE DECoUPLING RADIUS continues Figure 9: showing the results of experiment 6 when adjusting the dielectric constant higher. The peak noise voltage has decreased near the corners to 66mv, but only to 93.2mv at the current sink. Kirk Fabbri is owner of KsPT engineering Consulting llC and electrical engineer for l-3 Communications—Avionics systems. he can be reached at kirk.fabbri@l-3com.com. The most recent Mercedes automatic car looks just like a car on the outside but like a lounge from the inside. The car, based on the concept F 015 "luxury in Motion" showcased at the Consumer electronics show, is totally self-driving but has a brake and steering wheel if one wants to drive it manually. Tesla, Audi, Google and a number of other com- panies are trying to create their own adaptations of driverless cars, satisfying the predictions that they will be a reality on the roads possibly by the end of this decade. in fact, all the technology required for a self- driving car is already present. existing features such as self-parking preview and adaptive cruise control show what a fully automatic car can do. Driverless Cars to Renovate Automotive Industry

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