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April 2015 • The PCB Design Magazine 35 Barry olney is managing direc- tor of in-Circuit Design Pty ltd (iCD), Australia. The company developed the iCD stackup Planner and iCD PDN Plan- ner software, is a PCB Design service Bureau and specializes in board level simulation. To read past columns, or to contact olney, click here. beyond design LEARNING THE CURvE continues nology to be proven before jumping in. • This market, representing more than 65% of the total EDA software market, wants estab- lished technology at an affordable price. • Inadequate power delivery can exhibit in- termittent signal integrity issues. • The PDN must accommodate variances of current transients with as little change in power supply voltages as possible. • The AC impedance should be below the target impedance up to the maximum band- width (5 th harmonic). • As the frequency approaches half wave- length, the planes act as an unterminated transmission line and start to resonate. This resonance is not a problem unless it falls on the fundamental frequency or one of the odd har- monics. • The fundamental frequency generally has little radiation but then increases up to the 5 th harmonic and reduces again with the higher harmonics. • If the AC impedance is high at the funda- mental frequency or at any of the odd harmon- ics, the board will radiate. • Above 1GHz, there are a number of ways to reduce the AC impedance. The most effective being increasing planar capacitance and modi- fying the plane area. PCBDESIGN References: 1. Barry Olney's Beyond Design columns: PDN Planning and Capacitor Selection, Part 1 & Part 2; Power Distribution Network Planning 2. Geoffrey Moore: Crossing the Chasm For information on the ICD Stackup and PDN Planner, click here. French physicist Jean Charles Athanase Peltier discovered a key concept necessary for thermo- electric (Te) temperature control in 1834. his find- ings were so significant that Te devices are now commonly referred to as Peltier devices. since his work, there have been steady advancements in materials and design. Despite the technological sophistication Peltier devices, they are still less en - ergy efficient than traditional compressor/evapo- ration cooling. in the 1960s, Peltier devices were primarily made from Bismuth-Tel- luride (Bi2Te3) or Anti- mony-Telluride (sb2Te3) alloys and had a peak ef- ficiency (zT) of 1.1, mean- ing the electricity going in was only slightly less than the heat coming out. since the 1960s there have been incremental advancements in alloy technol- ogy used in Peltier devices. Te alloys are special because the metals have an incredibly high melting point. instead of melt- ing the metals to fuse them, they are combined through a process called sintering which uses heat and/or pressure to join the small, metallic granules. The applications for such a material are abun- dant. As new fabrication techniques are devel- oped, Peltier cooling devices may be used in place of traditional compression refrigeration systems. More importantly, as electrical vehicles and personal electronic devices become more ubiquitous in our daily lives, it is becoming in- creasingly necessary to have more efficient sys- tems for localized electri- cal power generation and effective cooling mecha- nisms. This new thermo- electric alloy paves the way for the future of mod- ern Te devices. Breakthrough in Thermoelectric Materials

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