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).
