If the CONTROL pin external capacitance (CT) should discharge
to the lower threshold, then the output MOSFET is turned off
and the control circuit is placed in a low-current standby mode.
The high-voltage current source turns on and charges the
external capacitance again. Charging current is shown with a
negative polarity and discharging current is shown with a
positive polarity in Figure 6. The hysteretic auto-restart
comparator keeps VC within a window of typically 4.7 to 5.7 V
by turning the high-voltage current source on and off as shown
in Figure 5(b). The auto-restart circuit has a divide-by-8
counter which prevents the output MOSFET from turning on
again until eight discharge-charge cycles have elapsed. The
counter effectively limits TOPSwitch power dissipation by
reducing the auto-restart duty cycle to typically 5%. Autorestart
continues to cycle until output voltage regulation is
again achieved.