Buffer sizing for delay uncertainty induced by process variations

Controlling the delay of a signal in the presence of various noise sources, process parameter variations, and environmental effects represents a fundamental problem in the design of high performance synchronous circuits. The effects of device parameter variations on the signal propagation delay of a CMOS buffer are described in this paper. It is shown that delay uncertainty is introduced due to variations in the current flow through a buffer. In addition, the variations in the parasitic resistance and capacitance of an interconnect line also affect the buffer delay. A design methodology that reduces the delay uncertainty of signals propagating along buffer-driven interconnect lines is presented. The proposed methodology increases the current flow sourced by a buffer to reduce the sensitivity of the delay on device and interconnect parameter variations.