Effect of the switching order on power dissipation in switched-capacitor circuits

The total power dissipation in a switched-capacitor circuit can be expressed as the sum of two terms: the static power absorbed by the operational amplifiers and the switching power, i.e., the power dissipated in charging and discharging the capacitors. It is shown that, in general, the switching power depends on the order in which the switches connected to the same clock phase are closed. In practice, it is impossible to know this order with absolute certainty. As a consequence, a realistic estimate of the power dissipation can only be given as a range of possible values. It is shown that upper and lower bounds on the power dissipation can be computed by solving a single-source shortest paths problem on a directed graph. Numerical results obtained on a number of switched-capacitor circuits indicate that, if low-power operational amplifiers are used, the switching power can be a significant fraction of the circuit's overall power dissipation.