With rapidly increasing switching speeds and surge current requirements, placement of local decoupling capacitors is becoming critically important in high-speed low-power designs. In this paper, utilizing the driving-point impedance (viewed from the device pin) as a metric, a new method is presented for the placement of decoupling capacitors in parallel-plate power ground pairs of high-speed circuits. In the proposed approach, instead of using the traditional trial-and-error method to identify an appropriate placement distance, the process is formulated in the form of a transcendental function. The resulting function is solved using Newton-Raphson (N-R) iterations to give a direct solution for the distance. Also, an analytical representation based on Hankel functions for the driving point impedance and its derivatives is developed to speed up the N-R iterations. The proposed method is validated by comparing the results with the full-wave electromagnetic simulations.

Additional Metadata
Keywords Capacitors, Decoupling capacitors, driving point impedance, Impedance, Microwave circuits, Pins, power delivery network, power integrity, Power measurement, printed circuit board, Rails, signal integrity, target impedance.
Persistent URL dx.doi.org/10.1109/TMTT.2017.2783382
Journal IEEE Transactions on Microwave Theory and Techniques
Citation
Erdin, I. (Ihsan), & Achar, R. (2018). Efficient Decoupling Capacitor Placement Based on Driving Point Impedance. IEEE Transactions on Microwave Theory and Techniques. doi:10.1109/TMTT.2017.2783382