Issue link: https://iconnect007.uberflip.com/i/1408619
36 DESIGN007 MAGAZINE I SEPTEMBER 2021 to use planar capacitance during the analysis. Planar capacitance is important as it dramati- cally reduces inductance at frequencies where decaps are out-of-range. Capacitor manufacturers are now mainly providing capacitor profiles in the form of S-parameter (S 11 ) data which makes analysis more difficult. Gone are the days when you could look at the V-curves from the capacitor ESL, ESR, and value. S-parameter data can be imported into the iCD PDN Planner to model the combination of decaps, planar capacitance, and mounting inductance. PDN issues impact the project schedule. By incorporating PDN simulation into your design process you can avoid the likelihood of a costly respin and a delay in the schedule. PDN Planners are now very affordable and so there is no reason why every product designer should not have access to the simulation tool. Key Points • PDN analysis is now a proven technology that should be adopted by mainstream developers. • e goal of robust PDN planning is to design a stable power source for all the required onboard power supplies. • One solution to reduce the PDN size is to combine up to eight DC-to-DC converters in the same IC package. • e trend in lower DC voltages also requires tighter voltage noise tolerances and higher currents. • e target impedance approach to analyzing the PDN is the combination of the worst-case transient current and the voltage noise specification, which act together to set the maximum allowable AC impedance with assured performance. • As current demands increase and voltage noise fluctuation tolerances reduce, we must lower the AC impedance even further with higher density capacitance. • Planar capacitor laminate or embedded capacitor materials are becoming a cost- effective solution to further improved power integrity. • Embedded capacitance technology pro- vides distributive decoupling capacitance and takes the place of conventional dis- crete decoupling capacitors over 1 GHz. • Ultra-thin laminates allow a significant layer count reduction in PCBs with better signal performance. • Increasing the converter switching fre- quency reduces the size of the PDN but is less efficient—producing more heat. • Switched tank converters create resonant tanks which require much less space than traditional switched capacitor converters. • Simulation is the key to resolving trade- offs. And, simulation allows the designer to perform what-if analysis of the PDN before the board assembly is produced. • It is imperative to be able to extract the plane data from the stackup and import the information into the PDN profile. is allows one to use planar capacitance during the analysis. • Capacitor manufacturers are now mainly providing capacitor profiles in the form of S-parameter (S 11 ) data. DESIGN007 Resources 1. Beyond Design: Learning the Curve, Plane Crazy Part 1 and Part 2, The Target Impedance Approach to PDN Design, Impact of PDN Imped- ance on EMI, by Barry Olney. 2. KEMET and Mouser Electronics: 7 Experts on New Approaches for Power Distribution Network Design - Mighty Guides 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 incorporat- ing the iCD Stackup, PDN, and CPW Planner. The software can be downloaded at www.icd.com.au. To read past columns or contact Olney, click here.