Patent ID: 8018699

Claim:
An over-voltage protection circuit for limiting the electrical power supplied via a low-power serial data bus to a computing apparatus in a machine, the circuit comprising: a long term voltage protection circuit including a first switch including a field effect transistor, the field effect transistor including a source terminal, a drain terminal, and a gate terminal, the first switch connecting an external interface to the computing apparatus when the first switch is in a closed position; and a second switch, including a first bipolar junction transistor including a first collector terminal, a first emitter terminal, and a first base terminal, and a second bipolar junction transistor including a second collector terminal, a second emitter terminal, and a second base terminal; and configured to sense the voltage level developed at the external interface and provide a control signal to open the first switch if the voltage at the external interface exceeds a predetermined threshold voltage to remove power from the low-power serial data bus and the computing apparatus, and wherein the gate terminal is connected to the first collector terminal, and the second base terminal is connected to the source terminal through a first resistor and the first emitter terminal is connected to a first reference voltage that approximates the predetermined threshold voltage.