Automatic Routing Algorithm for Differential Pair and Current Mirror in Analog Circuit Design

Differential pairs and current mirrors are basic building blocks in analog circuits. Routing is a crucial part of circuit design and directly determines circuits' performance. Existing papers on routing of analog circuits mostly use one fixed combination of metal layers and the placement is fixed. Such approach may result in wasted chip area and high production cost. This paper proposes an algorithm which can route differential pair and current mirror in flexible metal layer combinations, to be selected by designers. This algorithm considers routing symmetry, electro migration (EM) and voltage (IR) drop. It also adopts channel multiplexing and can adjust the row spacing of placement according to routing plan. Therefore, it effectively utilizes chip area and reduces cost. In addition, our algorithm automatically performs statistics on routing related data, making it easier to evaluate routing quality. The routing results show that under various metal layer combinations, our algorithm can successfully achieve high-quality routing for differential pair and current mirror with various placement forms.