Sgs-Thomson Microelectronics S.a.

Freeric Breugnot

Serge Fruhauf

Some integrated circuits need to be protected against malfunctioning due to the variations in the supply voltage Vcc. A detector of fast variations of the supply voltage is placed in the integrated circuit to interrupt or modify all or a part of the working of the general integrated circuit in the event of the occurrence of fast variation in Vcc. The detector includes a capacitor, a current limiter, a charging circuit, and a detection transistor. The current limiter is a transistor mounted as a diode. The charging circuit uses the supply voltage to charge the capacitor through the current limiter. The relatively stable voltage of the capacitor is applied to the gate of the detection transistor, which has a threshold voltage Vtp. The source of the detection transistor is connected to the voltage supply Vcc. If Vcc varies suddenly, the detector is made conductive. The assembly uses the difference between the threshold voltage Vtn of the current limiter and the threshold voltage Vtp of the detection transistor.

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Gournay Sur Marne, France

Freeric Breugnot