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December 2015 • The PCB Design Magazine 71 ELECTRICAL DESIGN CHALLENGES FoR AUToMoTIVE PCBS eye diagrams with stable signal density distribu- tions. These distributions are processed to pro- duce bathtub curves to reliably predict BER per- formance. These simulation approaches apply an impulse response to characterize the serial channel and then apply convolution methods to achieve their high-capacity throughput. Automotive Ethernet standards apply pulse amplitude modulation (PAM). The 1000BASE- T1 standard targets PAM-3, which means three logic signal levels exist on the channel instead of traditional two-level binary signals (Fig- ure 4). PAM-3 has significant implications for transceiver design as well as the modeling and simulation algorithms. Serial-link simulation software has been recently upgraded to support PAM for IBIS-AMI algorithms. As for transceiver IC design, it is a complex task to accommodate PAM signals in the many equalization algo- rithms, a task accomplished for PCB system de- sign software in parallel as part of general multi- level PAM signal support. Due to the application of PAM3, high at- tenuation and high levels of electromagnetic interference, 1000BASE-T1 designs use forward error correction (FEC). This technique applies Reed Solomon algorithms to boost BER to the required level. FEC is not applied for typical computing or telecom designs but has recently been implemented for PCB system design soft- ware to enable automotive Ethernet design. The final step to complete automotive Eth- ernet application for mainstream PCB system design is twofold. First, the IEEE standard must be finalized to fully know and implement the protocol compliance checks for serial link per- formance. Draft-level prototype implementa- tion of such compliance checks is now avail- able. Second, vendors must openly provide IBIS-AMI models for their chipset or IP blocks. This process is slow for computing and telecom device vendors but has become standard prac- tice and seems to be perceived as a market-en- try requirement by automotive Ethernet chip- set and IP vendors. Rapidly advancing market forces for ADAS and infotainment systems are driving (pun intended) these final steps to be completed sooner than many had envisioned necessary only months ago. In summary, as the automotive market goes through rapid changes, PCB Design teams must rise to the electrical challenges. Unique signal integrity challenges are faced by design teams due to the systemic nature of an automobile. With safety concerns at a premium, signal qual- ity concerns take a front seat to these chal- lenges. Modern PCB signal integrity tools must advance the features originally developed for computing, telecom and mobile designs to sup- port the automotive industry. Compliance tests for 1000BASE-T1 utilizing three logical signal levels (PAM-3) is just one example. PCBDESIGN Brad Brim is senior staff product engineer at Cadence Design Systems. He holds a PhD in electrical engineering. Future cell phones and other electronics could have batteries that charge in less than a minute. This new capability will be in part thanks to a space experiment using hard, flexible mate- rial as a clean power source. That potential future is scheduled for launch on the orbital ATK's S.S. Deke Slayton II Cygnus spacecraft atop a united launch Alliance Atlas v rocket Dec. 3. A team of students attending Desert Christian School in lancaster, California, with the support of NASA mentors and the uni- versity of California, los Angeles, developed the experiment. The experiment is designed to see how graphene-based supercapacitors charge, dis- charge and deteriorate in a microgravity envi- ronment. Future Batteries Could Charge in 30 Seconds article

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