Patent ID: 7450361
Filing Date: 2008-11-11
Classification: H03K

Abstract:
1. A semiconductor integrated circuit comprising: a power switch circuit for starting the output of an internal source voltage to be supplied to a semiconductor chip from an external source voltage supplied from outside said semiconductor chip; and an internal circuit into which said internal source voltage from said power switch circuit is supplied, wherein said power switch circuit further comprises an output transistor for, being supplied with said external source voltage, outputting said internal source voltage; a start-up circuit for controlling said output transistor so that the output current controlled to a predetermined value during the initial period following the turning “on” of an external power supply may flow in said output transistor; and a control circuit for controlling said start-up circuit, wherein said control circuit controls said start-up circuit in response to the turning “on” of the external power supply so that said start-up circuit may control said output transistor in such a way that said output current flowing in said output transistor during the initial period following the turning “on” of the external power supply may constitute effectively a constant increment as time passes, wherein said start-up circuit comprises a bias element for biasing said output transistor so that said output current controlled to said predetermined value may flow in said output transistor during said initial period following the turning “on” of said external power supply, wherein said start-up circuit comprises a first switch for relating the current value of said output transistor with the current value of said bias element during the initial period following the turning “on” of the external power supply and a startup current generating circuit for generating an output current constituting effectively a constant increment as the time passes during the initial period following the turning “on” of said external power supply, wherein said output current from said startup current generating circuit constituting effectively said constant increment during said initial period following the turning “on” of said external power supply is supplied to said bias element, said control circuit sets said first switch in the “on” state during the initial period following the turning “on” of said external power supply so that the current value of said output transistor may be related with the current value of said bias element, and said control circuit sets said first switch in the “off” state during said initial period following the turning “on” of said external power supply so that the current value of said output transistor may be effectively rendered unrelated with the current value of said bias element; further comprising a regulator for generating an internal source voltage to be supplied to said internal circuit out of said external source voltage received, wherein said control circuit controls said output transistor so that the fact that the difference between the value of said internal source voltage due to the charge of the load capacitance of said internal circuit with said output current of said output transistor during the initial period following the turning “on” of said external power supply and the value of said internal source voltage generated by said regulator is within a predetermined limit may be detected, and as a result of the detection any increase in said output current flowing in said output transistor for the passage of time may be stopped; further comprising a second switch connected between a voltage supply node to which any one voltage selected from said internal source voltage from said power switch circuit and said internal source voltage from said regulator is supplied and the output of said regulator, wherein after said increase in said output current flowing in said output transistor for the passage of time has been stopped based on said result of detection, said control circuit controls said second switch to be in the “on” state so that said internal source voltage generated by said regulator may be supplied to said internal circuit so that said internal source voltage generated by said regulator may be supplied to said voltage supply node as said selected one voltage.