Patent ID: 6031705
Filing Date: 2000-02-29
Classification: H02H

Abstract:
A surge protection circuit for use with at least one input of an integrated circuit, comprising:at least one input line for receiving at least one input signal;a surge detection device for detecting one of a positive surge condition and a negative surge condition of the at least one input line, wherein the surge detection device includes a threshold value switch and a Zener diode;a switching device that is capable of being activated by the surge detection device to interrupt the at least one input line, wherein the threshold value switch activates the switching device if a predefined switch-off threshold voltage is exceeded by the at least one input signal, and wherein the switching device includes an analog switch that is connected in series with the at least one input line and that assumes a high-resistance state when activated; anda logic circuit connected upstream from the surge detection device, wherein the at least one input line includes a first input line and a second input line, each one of the first input line and the second input line having an input terminal and an output terminal, wherein the analog switch includes a first field-effect transistor for monitoring the first input line and a second field-effect transistor for monitoring the second input line, wherein each one of the first field-effect transistor and the second field-effect transistor respectively includes a gate terminal, a drain terminal, and a source terminal, each gate terminal being jointly connected to an activating output of the threshold value switch, each drain terminal being connected to a corresponding input terminal of one of the first input line and the second input line, and each source terminal being connected to a corresponding output terminal of one of the first input line and the second input line, and wherein the logic circuit links instantaneous peaks of the input line and the input terminal of the second input line, and wherein the logic circuit includes a first diode and a second diode connected together in series at a common connection point between the first input line and the second input line, wherein a polarity of the first diode is opposite to a polarity of the second diode, and wherein the Zener diode has a terminal coupled to the common connection point of the first diode and the second diode.