| 摘要 |
PURPOSE:To reduce current consumption by providing an internal step-down power supply voltage equipped with a means to detect the impression of an external power supply voltage to a semiconductor device and a means to selectively activate first and second substrate bias impressing means in response to an output signal from this detecting means. CONSTITUTION:A ring oscillator 1 is provided to be operated with an external power supply voltage Vocc as an operation power supply voltage, and a ring oscillator 2 is provided to be operated with an internal power supply voltage Vicc, which is obtained by dropping the external power supply voltage, as the operation power supply voltage. Then, a charge pump circuit 3 is provided to supply a bias voltage to a semiconductor substrate in response to an oscillation signal f1 from the ring oscillator 1, and a charge pump circuit 4 is provided to impress the bias voltage to the semiconductor substrate in response to an oscillation signal f2 from the ring oscillator 2. By selectively operating the charge pump circuit 3 or 4 corresponding to a substrate potential, the optimum substrate bias voltage is stably supplied to the semiconductor substrate with the low current consumption. Thus, a substrate voltage generating circuit can be obtained with high reliability and low current consumption. |
