Common-centroid capacitor layout generation considering device matching and parasitic minimization

In analog layout design, the accuracy of capacitance ratios correlates closely with both the matching properties among the ratioed capacitors and the induced parasitics due to interconnecting wires. However, most of the previous works only emphasized the matching properties of a common-centroid placement, but ignored the induced parasitics after it is routed. This paper addresses the parasitic issue in addition to device matching during common-centroid capacitor layout generation. To effectively minimize the routing-induced parasitics, a novel common-centroid placement style, distributed connected unit capacitors, is presented. Based on the placement style, the ratioed capacitor layout generation flow and algorithms are proposed to simultaneously optimize the matching properties of a common-centroid placement and minimize the induced parasitics. Experimental results show that the proposed approach can greatly reduce area, wirelength, and routing-induced parasitics, and guarantee the best matching quality after routing.