Patent ID: 8689033

Claim:
A data processing device comprising an internal node, and a power supply and data signal interface for connection to an external line for conducting power and data signals between the data processing device and an external element, said power supply and data signal interface comprising: a switch having a current conduction path for connecting said external line and said internal node, and a control terminal for controlling said current conduction path, said switch being capable of withstanding an overvoltage condition on said external line; a controller for applying an enabling voltage to said control terminal, said enabling voltage enabling said current conduction path to supply current between said external line and said internal node in the presence of power supply to said controller and in the absence of said overvoltage condition on said external line; and a voltage reduction connection from said external line for applying a control voltage to said control terminal, said control voltage enabling said current conduction path to supply current between said external line and said internal node in the absence of power supply to said controller, said control voltage limiting a voltage applied to said internal node through said current conduction path in the presence of said overvoltage condition.