Methodology for placing localized guard rings to reduce substrate noise in mixed-signal circuits

A methodology is proposed to improve the efficacy of placing guard rings to reduce substrate coupling noise in mixed-signal circuits. The methodology is based on a localized guard ring structure within an aggressor circuit by redesigning the standard cells in a library. Specifically, a noise aware library is generated where each standard cell contains a dedicated substrate contact. This library is used within the aggressor block. Dedicated contacts within the cells generate a localized guard ring structure within each aggressor block. The proposed methodology achieves enhanced isolation as compared to conventional guard rings by minimizing the number of vertical current paths within the substrate.