Patent ID: 7944276

Claim:
A charge pump circuit for stepping up or down an input voltage to output a stepped-up or stepped-down output voltage, comprising: a pumping circuit; and a protection circuit, wherein the pumping circuit comprises: a pumping capacitance; a first drive transistor connected between an input node for receiving the input voltage and one terminal of the pumping capacitance; and a second drive transistor connected between an output node for outputting the output voltage and the one terminal of the pumping capacitance, wherein in a charge storing mode, the first drive transistor is turned ON to store charge in the pumping capacitance, while in a charge transfer mode, the second drive transistor is turned ON to transfer the charge stored in the pumping capacitance to the output node, and if the output voltage is lower than a judgment voltage during stepping up then the protection circuit puts at least one of the first and second drive transistors in a high-resistance state in which the resistance value is higher than when the transistor is ON, said judgment voltage is equal to or lower than the input voltage.