Walking pads: Fast power-supply pad-placement optimization

Abstract

Abstract-We propose a novel C4 pad placement optimization framework for 2D power delivery grids: Walking Pads (WP). WP optimizes pad locations by moving pads according to the "virtual forces" exerted on them by other pads and current sources in the system. WP algorithms achieve the same IR drop as state-of-theart techniques, but are up to 634X faster. We further propose an analytical model relating pad count and IR drop for determining the optimal pad count for a given IR drop budget.

Walking Pads

“…Prior work has targeted resistive voltage noise (IR drop) and optimized pad location and number to minimize worstcase IR drop [13,14,16,18,19]. All these state-of-the-art pad placement techniques focus on steady-state analysis and VDD pads only.…”

Architecture implications of pads as a scarce resource

“…For example, Wang et al [35] evaluated the impact of pad placement on chip IR drop and proposed an optimization algorithm to minimize global IR drop. Zhang et al [39] also used IR drop as a figure of merit and examined the impact of C4 pad count on technology scaling.…”

“…2, the number and locations of C4 pads have a significant effect on power delivery quality. To avoid sub-optimal pad allocation, we adopt the simulatedannealing algorithm described in [35] and extend it to jointly optimize both Vdd and ground pad locations.…”

“…As a result, delivering a stable voltage supply to switching transistors is increasingly challenging. The optimization of the power delivery network's (PDN's) physical structure (e.g., metal layer geometry [19], decoupling capacitor distribution [29] and controlled collapse chip connection (C4) pad location [35]) helps to reduce supply noise, and to date, noise can generally be handled with modest guardbands (i.e., slight under-clocking and/or overvolting). However, power delivery difficulties arise and will get worse for several reasons.…”

IGS: The Novel Fast IC Power Ground Network Optimization Flow Based on Improved Gauss-Seidel Method

“…[4] presents the analysis method of Graphene-Based power distribution networks. A Walking pads method is presented in [5] and [6], which reduces IR-drop by changing the position of power supply pads according to critical path. But the changed power pads lead to distribution problem.…”