| 摘要 |
PURPOSE:To improve a switchover to high voltage by prohibiting the charging of load capacity by turning off a transfer gate circuit in case the electric poten tial is higher than power potential. CONSTITUTION:A power supply voltage switching circuit is such that gates of (n) channel MOS transistors(Tr) T9 and T10 are commonly connected at a node N10 respectively, and that drains are also connected to a high voltage terminal VPP each other. A charge pump circuit is connected between a gate and source of the Tr T10. This pump circuit is constituted of a Tr T12 and a capacitor C4. A node N8 is the output from a decoder, and the Tr T8 is con nected between nodes N8 and N9. When the node N8 reached a high level, the node N9 is lifted to high voltage. According to the constitution, the potential difference that the potential of a gate commonly connected at one cycle of a clock supplied to the pump circuit is boosted is getting big, and even the power supply of a low voltage can get high voltage. |
