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Design007-Nov2018

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44 DESIGN007 MAGAZINE I NOVEMBER 2018 Further Reading • Beyond Design: Power Distribution Net- work Planning by Barry Olney, The PCB Maga- zine, May 2012. • Beyond Design: Plane Crazy, Part 1 by Barry Olney, The PCB Design Magazine, December 2015. • Beyond Design: The Target Impedance Approach to PDN Design by Barry Olney, Design007 Magazine, February 2018. • High-Speed Digital Design: A Handbook of Black Magic, First Edition by Howard Johnson and Martin Graham, Prentice Hall, 1993. Barry Olney is managing director of In-Circuit Design Pty Ltd (iCD), Australia, a PCB design service bureau that specializes in board- level simulation. The company developed the iCD Design Integrity software incorporating the iCD Stackup, PDN, and CPW Planner. The software can be downloaded from www.icd.com.au. To read past columns or contact Olney, click here. • Split ground planes create discontinuities of impedance, crosstalk, and EMI, and should not be used • The ground planes should not be split, but partitioned instead • The goal of PDN planning is to design a stable power source for all the required power supplies • Each component of the PDN has a specific resonant frequency where the impedance will be low • PDN components interact to create anti-resonance peaks that may occur at undesirable frequencies • The further the PDN impedance is above the target impedance, the greater the risk of intermittent operation or even complete product failure • Decoupling capacitors are only effective up to about 200 MHz; above that, only on-die capacitance or planar capacitance can reduce the PDN impedance significantly Figure 6: Optimized PDN for a 1066 MHz DDR3 (iCD PDN Planner).

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