Semiconductor integrated circuit with an internal voltage generating circuit requiring a reduced occupied area

摘要

A semiconductor integrated circuit includes a charge pump for issuing an internal power supply voltage higher than an external power supply voltage, two level detectors for detecting a magnitude of the internal power supply voltage issued from the charge pump, and a composite ring oscillator including two ring oscillators connected to these level detectors and having different oscillation frequencies, respectively. Depending on the magnitude of the internal power supply voltage issued from the charge pump, the signals generated by the ring oscillators are selectively issued to the charge pump.