| 摘要 |
PURPOSE:To hold an output voltage within a proper constant range at all times by connecting clamping element groups which differ in clamp voltage in parallel and placing and operating the clamping element group which is large in clamp voltage in an area where the source voltage is low and the clamping element group which is small in clamp voltage in an area where the source voltage is high. CONSTITUTION:The clamping element groups 2 and 3 which have the mutually different clamp voltages are connected between the output voltage VCP of a charge pump 1 and the source voltage VDD in parallel. Before the clamp voltage by the clamping element group 2 which is large in clamp voltage exceeds the output voltage VCP, a switching circuit 4 interrupts the clamping operation by the clamping element group 2 which is large in clamp voltage and starts the clamping operation by the clamping element group 3 which is small in clamp voltage. Consequently, even if the clamp voltage varies as the source voltage VDD varies, the output voltage VCP of the charge pump 1 can be held within the proper constant range at all times. |
