Low leakage current LED drive apparatus with fault protection and diagnostics

Drive apparatus for an LED, comprising:

• a controller having an I/O port selectively configurable as an output or an input, said I/O port being coupled to a control terminal of the drive apparatus;
• a FET having an input coupled to said control terminal, and an output coupled to the LED via an output terminal of the drive apparatus for selectively completing a current path through the LED to selectively turn the LED ON and OFF;
• a diagnostic interface circuit including a transistor having an input coupled to the output terminal of said drive apparatus and a output coupled to the control terminal of said drive apparatus, said transistor having a conduction state that is diagnostic of an output fault condition;
• and
• control means effective at a desired ON-to-OFF or OFF-to-ON transition of said LED to first configure said I/O port as an output for a predetermined interval to initiate the desired transition of said LED, and then re-configure said I/O port as an input for sampling a voltage at said control terminal to determine the conduction state of said transistor and diagnose said output fault condition.