Patent ID: 6392392
Filing Date: 2002-05-21
Classification: H03K

Abstract:
A semiconductor integrated circuit comprising:an output transistor connected between an output terminal and a power source; an OCD circuit which detects a current passing through said output transistor, said OCD circuit having: a constant-current source which generates a first constant current having a given temperature characteristic on the basis of a reference voltage, said given temperature characteristic being substantially equal to a temperature characteristic of said output transistor; a current mirror circuit which generates a second constant current on the basis of said first constant current; a current-voltage converting circuit which generates a reference voltage on the basis of said second constant current; and a comparator which compares said reference voltage with a voltage at said output terminal; and a logic circuit which controls a conduction state of said output transistor on the basis of an input signal, said logic circuit causing said output transistor to be in a nonconductive state in response to generation of an output signal from said comparator, whether said input signal is inputted or not; wherein the constant-current source comprises n diodes connected in series with a first resistor, the current-voltage converting circuit comprises a second resistor, and wherein n is an integer nearest a value N defined as follows: N=âˆ’(R1Ã—IS/mR2)Ã—(&dgr;Ron/&dgr;T)/(&dgr;VF/&dgr;T); â€ƒwherein: R1 is a resistance of the first resistor; R2 is a resistance of the second resistor; m is a transfer characteristic of the current mirror circuit; Is is a current flowing through the output transistor; &dgr;Ron/&dgr;T is a temperature coefficient of an ON-state resistance of the output transistor; and &dgr;VF/&dgr;T is a temperature coefficient of a forward direction voltage of each said diode.