A power supply controller having a multi-function terminal. In one embodiment,
a power supply controller for switched mode power supply includes a drain terminal,
a source terminal, a control terminal and a multi-function terminal. The multi-function
terminal may be configured in a plurality of ways providing any one or some of
a plurality of functions including on/off control, external current limit adjustments,
under-voltage detection, over-voltage detection and maximum duty cycle adjustment.
The operation of the multi-function terminal varies depending on whether a positive
or negative current flows through the multi-function terminal. A short-circuit
to ground from the multi-function terminal enables the power supply controller.
A short-circuit to a supply voltage from the multi-function terminal disables the
power supply controller. The current limit of an internal power switch of the power
supply controller may be adjusted by externally setting a negative current from
the multi-function terminal. The multi-function terminal may also be coupled to
the input DC line voltage of the power supply through a resistance to detect an
under-voltage condition, an over-voltage condition and/or adjust the maximum duty
cycle of power supply controller. Synchronization of the oscillator of the power
supply controller may also be realized by switching the multi-function terminal
to power or ground at the desired times.
