Patent ID: 7254002

Claim:
A protection circuit for preventing reverse conduction through a lower voltage driver that is coupled to a first node when a higher voltage driver coupled to the first node is driving the first node to a voltage higher than the maximum voltage of the lower voltage driver, wherein the lower voltage driver includes an output stage having a first transistor having a first current flow terminal coupled to a lower voltage rail and a second current flow terminal coupled to drive the first node, the circuit comprising: a second transistor having a first current flow terminal coupled to the second current flow terminal of the first transistor and a second current flow terminal coupled to the first node, and further having a control terminal; a comparator coupled to detect when a voltage on the first node exceeds the voltage of the lower voltage rail, the comparator having an output coupled to the control terminal of the second transistor and configured to turn the second transistor off if the voltage on the first node exceeds the voltage of the lower voltage rail; and a diode clamp coupled between the control terminal and the first current flow terminal of the second transistor.