Decoupling capacitor sizing and placement

Abstract

A method and system for reducing noise in a power grid of an integrated circuit, which optimizes the placement and sizing of decoupling capacitors in the power grid. Logic cells are located in a first layout of the integrated circuit with empty spaces between the adjacent cells, and the placement of the cells is changed to a second layout wherein the size of the empty spaces between the adjacent cells also change. The decoupling capacitors are placed in the empty spaces of the second layout. In the example of a row-oriented cell structure, the empty spaces may be uniformly distributed along each row for the initial layout. An adjoint sensitivity analysis is performed of the sensitivity of a noise function of the integrated circuit with respect to sizes of the empty spaces between adjacent cells, and an original noise waveform is convolved with an adjoint noise waveform. The convolution may use piecewise linear compressions of the original and adjoint noise waveforms. A quadratic programming solver is then used to iteratively determine the sizes of the empty spaces between adjacent cells.