A two-wire power delivery system comprising: a passive protection circuit in a mobile device with a two-wire power interface that includes two power pins; a control circuit, external from the mobile device, wherein the control circuit is powered by a high-side power supply (V H) and a low-side power supply (V L), and wherein the control circuit is configured to detect a voltage at a detect pin and generate one or more control signals; and a switch circuit, external from the mobile device, that is configured to selectively control connections between the two power pins (PIN1, PIN2) of the mobile device and one or more of the high-side power supply, the low-side power supply, and the voltage detect pin of the control circuit, such that: in an IDLE state; in a TEST state, one of the two power pins (PIN1, PIN2) of the mobile device is coupled to one of the high-side power supply and the low-side power supply by the switch circuit, and the other of the two power pins (PIN1, PIN2) is coupled through a series resistor to the other of the high-side power supply and the low-side power supply which corresponds to the detect pin of the control circuit, wherein the control circuit determines an orientation of the two power pins based on a detected voltage at the detect pin; and in a CONNECT state, one of the two power pins is coupled to one of the high-side power supply and the low-side power supply by the switch circuit, and the other of the two power pins is coupled to the other of the high-side power supply and the low-side power supply by the switch circuit based on the determined orientation, characterized in that the switch circuit is configured to decouple the two power pins (PIN2, PIN2) from external power. a passive protection circuit in a mobile device with a two-wire power interface that includes two power pins; a control circuit, external from the mobile device, wherein the control circuit is powered by a high-side power supply (V H) and a low-side power supply (V L), and wherein the control circuit is configured to detect a voltage at a detect pin and generate one or more control signals; and a switch circuit, external from the mobile device, that is configured to selectively control connections between the two power pins (PIN1, PIN2) of the mobile device and one or more of the high-side power supply, the low-side power supply, and the voltage detect pin of the control circuit, such that: in an IDLE state; in a TEST state, one of the two power pins (PIN1, PIN2) of the mobile device is coupled to one of the high-side power supply and the low-side power supply by the switch circuit, and the other of the two power pins (PIN1, PIN2) is coupled through a series resistor to the other of the high-side power supply and the low-side power supply which corresponds to the detect pin of the control circuit, wherein the control circuit determines an orientation of the two power pins based on a detected voltage at the detect pin; and in a CONNECT state, one of the two power pins is coupled to one of the high-side power supply and the low-side power supply by the switch circuit, and the other of the two power pins is coupled to the other of the high-side power supply and the low-side power supply by the switch circuit based on the determined orientation, characterized in that the switch circuit is configured to decouple the two power pins (PIN2, PIN2) from external power. in an IDLE state; in a TEST state, one of the two power pins (PIN1, PIN2) of the mobile device is coupled to one of the high-side power supply and the low-side power supply by the switch circuit, and the other of the two power pins (PIN1, PIN2) is coupled through a series resistor to the other of the high-side power supply and the low-side power supply which corresponds to the detect pin of the control circuit, wherein the control circuit determines an orientation of the two power pins based on a detected voltage at the detect pin; and in a CONNECT state, one of the two power pins is coupled to one of the high-side power supply and the low-side power supply by the switch circuit, and the other of the two power pins is coupled to the other of the high-side power supply and the low-side power supply by the switch circuit based on the determined orientation, characterized in that the switch circuit is configured to decouple the two power pins (PIN2, PIN2) from external power.