Patent ID: 6392394
Filing Date: 2002-05-21
Classification: G05F

Abstract:
A step-down circuit for reducing external supply voltage to be supplied from the outside to supply it to an internal circuit, comprising:a diode circuit for reducing said external supply voltage by desired voltage to output it as internal supply voltage; a pull-down transistor for pulling down said internal supply voltage to be outputted from said diode circuit when said external supply voltage drops; and a controlling circuit for controlling an operation of said pull-down transistor, wherein said diode circuit has step-down transistors inserted between said external power supply and said controlling circuit, wherein said step-down circuit has a compensation circuit for controlling source-drain voltage of said step-down transistor to a desired value, and wherein said compensation circuit comprises compensation transistors to be inserted in series between said external power supply and grounding potential, to whose gates predetermined reference voltage is applied so as to provide such on-resistance as to offset temperature dependence of said step-down transistors, at least one resistor to be connected in series to said compensation transistors, and a capacitor to be inserted between connecting portions between said resistor and said compensation transistors, and said external power supply.