An integrated circuit includes a control circuit and first to second voltage generation circuits. The control circuit is coupled between a first voltage terminal providing a first supply voltage and a first node coupled to a first capacitive unit. The first voltage generation circuit includes at least one first transistor that has a source terminal receiving a second supply voltage, a drain terminal coupled to a second node in contact with a second capacitive unit, and a gate terminal coupled to the first node. The second voltage generation circuit is coupled to the first voltage terminal and the first and second nodes. Firstly the control circuit turns on the at least one first transistor to adjust a voltage level of the second node to have the second supply voltage. The second voltage generation circuit adjusts a voltage level of the first node to have the first supply voltage.