Fast analysis and optimization of power/ground networks

Abstract

This paper presents an efficient method for optimizing power/ground (P/G) networks by widening wires and adding decoupling capacitors (decaps). It proposes a structured skeleton that is intermediate to the conventional method that uses full meshes (which are hard to analyze efficiently), and treestructured networks (which provide poor performance). As an example, we consider a P/G network structure modeled as an overlying mesh with underlying trees originating from the mesh, which eases the task of analysis with acceptable performance sacrifices. A fast and efficient event-driven P/G network simulator is proposed, which hierarchically simulates the P/G network with an adaptation of PRIMA to handle non-zero initial conditions. An adjoint network that incorporates the variable topology of the original P/G network, as elements switch in and out of the network, is constructed to calculate the transient adjoint sensitivity over multiple intervals. The gradients of the most critical node with respect to each wire width and decap are used by a sensitivity-based heuristic optimizer that minimizes a weighted sum of the wire and the decap area. Experimental results show that this procedure can be used to efficiently optimize large networks.

Efficient power/ground network analysis for power integrity-driven design methodology

“…The problem of power/ground (P/G) network synthesis has been studied extensively in the literature [1,2,3,6,7,8,9,10,11,12]. An important problem of P/G network synthesis is to use the minimum amount of silicon area for wiring P/G network under the constraint of potential reliability such as IR drops and electromigration.…”

Partition-based algorithm for power grid design using locality

“…Typically, the choices available to a supply net designer are to (i) appropriately size the supply net wires [1][2][3][4], (ii) perform topology optimization, i.e., to assign suitable pitches to the power grid wires and/or determine the optimal assignment of the pins to the pads and placement of pads on the power grid [5][6][7][8][9], and (iii) add decoupling capacitors [10], [11].…”

“…Schemes for automated power distribution network design can be divided into the following two categories, based on tradeoffs between the accuracy of the embedded power grid simulator and the level of sophistication of the optimizer: (A) Heuristic iterative optimization methods, employing an explicit and exact circuit analysis step in the main optimization loop to determine constraint violations in the power grid [6], [10].…”

Congestion-aware topology optimization of structured power/ground networks

“…The wire sizing and decap placement methods of [1][2][3][4][5][6] all assume that the topologies of P/G networks are fixed, and only the widths of the wire segments and the positions of decaps need to be determined. The wire sizing and decap placement solutions to P/G network designs have a significant cost of over-utilization of the chip area.…”

“…The key constraints in the design of power supply network are those of IR drop, electromigration and ground bounce due to inductive effects. To meet these constraints, the typical techniques available to the designers of supply networks are (i) wire sizing [1][2][3][4], (ii) adding decoupling capacitors (decaps) [5,6], and (iii) using appropriate topologies for the P/G network [7][8][9].…”