Optimized design of high fan-in multiplexers using switches with driving capability

In this communication, a strategy to design fast multiplexers with high fan in is proposed. It is based on the recently proposed architecture heterogeneous tree (Lin, IEEE Trans. on CAS, pt. I, vol. 19, no. 18, pp. 963-967, 2000), which until now has been optimized assuming only CMOS switch-based implementation with transmission gates or pass transistors. In this work the design strategy of heterogeneous-tree multiplexers is extended to the case of switches with driving capability, like clocked inverters. It provides design criteria to minimize the delay, which are general and simple to be applied, and thus are helpful from the early design phases. Moreover, performance achievable is analytically expressed for a given fan in and CMOS process. As an example, a multiplexer designed with the strategy proposed and with a fan in of 256 is simulated using a 0.35-μm CMOS process. The predicted delay agrees well with the simulated value