A switched capacitor circuit simulator

Abstract:

This paper describes the modeling and simulation of switched capacitor circuits in AWEswit. AWEswitis a mixed signal simulator for switched capacitor circuits. It allows for portions of the circuit to be modeled with digital blocks controlled by an event queue. The remainder of the circuit is modeled in the analog domain. The paper describes the circuit formulations employed by AWEswit, and how they are exploited in modeling the nonidealities associated with switched capacitor circuits.
AWEswit employs asymptotic waveform evaluation (AWE) as its core simulation engine. It combines circuit formulations in the charge-voltage and current-voltage regimes. This flexibility in the circuit formulations means that if the circuit is modeled entirely with ideal switches (Le., no resistors), then it is automatically solved in the chargevoltage regime (like SWITCAP2). However,
if portions of the circuit need to be solved in the current-voltage regime, then AWEswit automatically partitions the circuit and solves the different partitions in whichever regime is appropriate, i.e., in the current-voltage regime (using AWE to evaluate circuit response) or in the chargevoltage regime. AWEswit naturally handles the bandwidth limitations associated with switched capacitor circuits. In addition, it models the clock feedthrough and signal-dependent charge dump that characterize MOSFET  switches. The simulator is illustrated by example.


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