Switched-Capacitor Low-Pass Filter with Pole Frequency Tuning at Constant Frequency of Switching

The circuitry of a switched-capacitor low-pass filter (SCF) is considered, in which it is possible to tune the pole frequency without changing the capacitances of the switched capacitors, for example, by selecting them of the same kind. To study the suggested SCF circuit, the analysis in the time domain was used, and the obtained characteristics of the SCF were further compared with the characteristics of a generalized second-order analog filter. It is shown that the parameters implemented by the suggested filter depend not only on the capacitance values of the switched capacitors, but also on the ratio of the resistances of two additional resistors. Moreover, the SCF pole frequency is determined by the switching frequency of the keys, the ratios of the capacitances of the switched capacitors, as well as the ratio of the resistances of additional resistors. Due to the goal-oriented selection of the resistances of these resistors, it is possible to lower the SCF pole frequency at constant and identical values of the capacitances of the switched capacitors.