Patent ID: 7782585

Claim:
A semiconductor integrated circuit device comprising: a power transistor operable for switching control to be performed thereon; and an overheat protection circuit for detecting an abnormal rise in temperature of the power transistor and notifying a circuit to be protected of the abnormal rise in temperature, wherein the overheat protection circuit comprises: a filter portion for removing, from a power supply voltage thereof, a frequency component that is higher than a predetermined cut-off frequency, reference voltage producing circuitry to produce a predetermined reference voltage; a bipolar transistor for temperature detection that is provided next to the power transistor, wherein the bipolar transistor is operable to be turned on/off according to whether a base-emitter forward voltage drop which varies depending on an ambient temperature, is higher or lower than the reference voltage; control voltage signal generating circuitry for generating from the power supply voltage a control voltage signal having a logic according to an on/off state of the bipolar transistor; switch circuitry operable to be turned on/off according to the logic of the control voltage signal; and overheat protection signal generating circuitry to generate an overheat protection signal having a logic according to an on/off state of the switch circuitry, wherein, as the filter portion, the overheat protection circuit further comprises: a resistor disposed between one end of the switch circuitry and a point to which the power supply voltage is to be applied; and/or a capacitor disposed between another end of the switch circuitry and ground.