A recursive algorithm for estimating the internal charge sharing effect in RC tree circuits

BTS (Binary-tree Timing Simulator) is a waveform-based switch-level timing simulator for VLSI circuits and the primary goal is to obtain an accurate waveform during the transient period. To achieve high accuracy, the internal charge effect should be considered because the delay behavior of a CMOS gate is dramatically influenced by internal charges stored in the internal nodes. However, the delay estimation will become a difficult problem when the charge sharing effect is considered. Therefore, this paper presents a recursive algorithm based on Modified Threaded Binary (MTB) tree for efficiently performing the internal-charge-delay estimation in transistor groups using the switch-level delay model. The algorithm CSEE (Charge Sharing Effect Estimation) can determine the charge distribution among the internal nodes, and then increases the accuracy of the waveform approximate technique used in BTS.