Appliance Design - February 2009 - (Page 37)

SHIELDING & EMI Fig. 10. Active FPGA demonstration board. Fig. 11. Data comparisons: X2Y capacitors vs. conventional MLCCs. Location benefits Power switchers inside a product can propagate noise outside the product by way of power cables. Traditional AC filter solutions combine multiple passive components on a dedicated printed circuit board (PCB). Physically locating many components at the power lead exit is simply not possible. At high frequencies, wire lengths connecting the components in a filter network degrade high frequency filter performance. In many cases, a large ferrite is integrated into the AC power cord as a secondary measure to meet EMC compliance requirements that can go to 1GHz or higher frequencies. Schurter’s 5150 filtered IEC connector solves the proximity issue by integrating a single X2Y AC capacitor inside the connector, which can eliminate multiple passive components used for high-frequency filtering and their associated PCB. The 5150 connector can be ideally located at the AC power cable I/O to deliver optimized high frequency EMI filtering. (See Fig. 9.) and LCD drivers, to name a few. Logic transition with fast signal edges can result in EMI issues as printed circuit boards with copper planes and traces become resonant structures. To evaluate real world performance, X2Y and industry experts [8, 9] built an active FPGA board [10] to demonstrate passive component reduction and noise reduction on the I/O power plane. (See Fig. 10.) The power island surrounding the FPGA supports the bypass capacitors used for the power delivery network (PDN) supporting the IC. To directly compare performance, capacitor mounting pads for 16 X2Y 0603 capacitors and up to 64 conventional 0402 capacitors were located around all four sides of the FPGA. The left and right FPGA I/O banks drive 50 Ohm transmission lines: 60 lines from each 6 banks terminate on the left and right side of PCB. An SMA connector shown at the top right of the FPGA power island was used to probe I/O voltage with the FPGA driving all 360 of the left and right bank outputs simultaneously. (See Fig. 11.) An oscilloscope was used to compare the various capacitor configurations and peakto-peak noise voltage results on the I/O power plane at the SMA connector. The following networks were measured: 4No capacitors, which yielded maximum peak-peak noise and caused IC malfunction. Power plane noise Today, even modest appliances use integrated circuits (ICs). Many appliances use programmable logic [7] (FPGAs) to manage a variety of functions that include motor control, power management, network interface, www.applianceDESIGN.com Fig. 12. Wireless phone, and a cell phone tower. applianceDESIGN February 2009 37 http://www.appliancedesign.com

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Appliance Design - February 2009 Contents Editorial Shipments/Forecasts News Watch Force-Sensing Technology Offers Designers an Alternative Approach to Creating Touch-Control Interfaces A Flammable Vapor Sensing Technology that was Originally Developed for use in Water Heaters has Evolved for use in a Broader Array of Applications Latches, Hinges, and Slides Must Reliably Secure Parts Together, Sometimes for Hundreds of Thousands of Cycles. Beyond their Utilitarian Functions, They Can Also Change Consumer Perceptions Elastomeric Electrical Connectors Can Solve Space Constraint Problems in Electronic Products and Provide Some Cost Advantages as Well A Multi-Layer Ceramic Capacitor with a Novel Electrode Design Can Suppress Electromagnetic Interference, Improve Circuit Performance, and Reduce the Number of Needed Components Design Marts Association Report: AHRI Advertisers’ Index

Appliance Design - February 2009

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