US Patent 7304528 Charge pump with speed control

A charge pump circuit includes a test mode control unit for generating a plurality of control signals according to a test mode enable signal and an input signal and fixing one of the plurality of the control signals depending upon whether a fuse has been cut or not, a ring oscillator for outputting an output frequency of which varies according to an output of the test mode control unit, and a charge pump for generating a high voltage, which is higher than an external voltage, according to an output of the ring oscillator.