Voltage down converter allowing supply of stable internal power supply voltage

摘要

A voltage down converter includes a first voltage down converting circuit and a second voltage down converting circuit. The first voltage down converting circuit supplies an internal power supply voltage VCCS1 to an internal circuit only during a period T when the internal power supply voltage VCCS1 falls below a predetermined voltage according to a signal DCE. In the first voltage down converting circuit, P channel MOS transistors are selectively activated according to the levels of the plurality of voltages, and a voltage down converting partial circuit supplies a current of an amount corresponding to the level of the external power supply voltage VCC to a power supply node. As a result, even during the period T, the internal power supply voltage can be maintained at a level of the reference voltage.