Asymmetric-Amplitude Dual-Polarity Charge Pump With Four-Phase Selectable Operation

摘要

A symmetric dual-voltage charge pump and its control circuit generate bipolar output voltages. The charge pump converts a unipolar power source to a set of dual-voltage outputs of opposite polarity that are completely independent of each other. The charge pump includes two voltage-boosting transfer capacitors and two output capacitors. Two-phase operation generates an increased-magnitude output voltage of a negative polarity and another two phases of operation generate an increased output voltage of a positive polarity. The charge pump selectively charges one or both of the bipolar outputs with individual 2-phase charge cycles or with a sequence of charge cycles. When controlled by comparators with unequal reference voltages, the charge pump can force the bipolar outputs to unequal positive and negative voltages. Charge pumping is faster since only 2 phases are needed for charging either the positive or negative output.