Global PCB Connections: A Field Engineer’s Perspective on the Top 10 Trends to Watch
Target Condition: Designing vs. Inventing
Dana on Data: The Missing AI-NPI Link
Systematic Estimation of Worst-Case PDN Noise: Target Impedance and Rogue Waves
February 1, 2016 | Istvan Novak, OracleEstimated reading time: 1 minute
In the dark ages of power distribution design, the typical advice was to use a bulk capacitor and one 0.1uF bypass capacitor for every power pin on the digital circuit. This was very unscientific, but served the industry reasonably well in low-density and low-speed circuits. As the designs got more demanding, the target impedance concept was developed [1]. Using a target impedance, designers had a metric and a design goal to guarantee that the voltage transients stay within specified limits.
Strictly speaking, the target-impedance concept is valid only for flat self-impedance profiles; however, most of our practical designs do not have that luxury. With non-flat impedance profiles, the noise is different. Surprisingly and counterintuitively, keeping the same maximum impedance, the more we deviate from the flat impedance by pushing the impedance down in certain frequency ranges, the higher the worst-case transient noise becomes. This raises the question how to do a systematic design and also gives rise to speculations about rogue waves [2]. But there is a systematic, fast and efficient way of calculating the worst-case noise for any arbitrary impedance profile.
The target impedance concept assumes that the power distribution network is hit by a series of current steps, each current step having a magnitude of DI and fastest transition time of ttr. If up to the BW bandwidth of the excitation the PDN impedance is Ztarget, the resulting voltage transients are within the DV limits.
To read this entire article, which appeared in the December 2015 issue of The PCB Design Magazine, click here.
Share on:
Suggested Items
Intervala Hosts Employee Car and Motorcycle Show, Benefit Nonprofits
08/27/2024 | IntervalaIntervala hosted an employee car and motorcycle show, aptly named the Vala-Cruise and it was a roaring success! Employees had the chance to show off their prized wheels, and it was incredible to see the variety and passion on display.
KIC Honored with IPC Recognition for 25 Years of Membership and Contributions to Electronics Manufacturing Industry
06/24/2024 | KICKIC, a renowned pioneer in thermal process and temperature measurement solutions for electronics manufacturing, is proud to announce that it has been recognized by IPC for 25 years of membership and significant contributions to electronics manufacturing.
Boeing Starliner Spacecraft Completes Successful Crewed Docking with International Space Station
06/07/2024 | BoeingNASA astronauts Barry "Butch" Wilmore and Sunita "Suni" Williams successfully docked Boeing's Starliner spacecraft to the International Space Station (ISS), about 26 hours after launching from Cape Canaveral Space Force Station.
KIC’s Miles Moreau to Present Profiling Basics and Best Practices at SMTA Wisconsin Chapter PCBA Profile Workshop
01/25/2024 | KICKIC, a renowned pioneer in thermal process and temperature measurement solutions for electronics manufacturing, announces that Miles Moreau, General Manager, will be a featured speaker at the SMTA Wisconsin Chapter In-Person PCBA Profile Workshop.
The Drive Toward UHDI and Substrates
09/20/2023 | I-Connect007 Editorial TeamPanasonic’s Darren Hitchcock spoke with the I-Connect007 Editorial Team on the complexities of moving toward ultra HDI manufacturing. As we learn in this conversation, the number of shifting constraints relative to traditional PCB fabrication is quite large and can sometimes conflict with each other.