Method and apparatus for programming a power converter controller with an external programming terminal having multiple functions

A power converter, comprising:

• an energy transfer element coupled between an input of the power converter and an output of the power converter;
• a power switch coupled the energy transfer element and the input of the power converter;
• a control circuit coupled to generate a switching signal to control switching of the power switch in response to a feedback signal representative of the output of the power converter to control a transfer of energy from the input of the power converter to the output of the power converter;
• a programming interface circuit coupled to the control circuit;
• a coupling switcher coupled to the programming interface circuit;
• and
• a programming terminal selectively coupled to the programming interface circuit through the coupling switcher, wherein a programming circuit coupled to the programming terminal is coupled to the programming interface circuit through the coupling switcher during a startup programming condition and during a fault condition of the power converter, wherein the programming circuit coupled to the programming terminal is decoupled from the programming interface circuit by the coupling switcher during a normal operating condition of the power converter.