A switching power regulator for performing DC-to-DC conversion may be
implemented with a soft-start circuit configured to ensure orderly
power-up of the switching power regulator by controlling the maximum
output current delivered to a load while maintaining proper voltage
regulation during start-up. The soft-start circuit may use combinations
of reference voltages generated by a reference voltage digital-to-analog
converter and a programmable width burst-pulse to control an output
voltage of the switching power regulator during start-up without
requiring external components. The soft-start circuit may provide
burst-pulses directly to a drive circuit configured in the switching
power regulator to control the output voltage of the switching power
regulator, thereby beginning to ramp up the output voltage of the
switching power regulator from zero volts. A specified number of clock
cycles after the output voltage has reached a specified value, the
soft-start circuit may switch control of the drive circuit from the burst
pulses to regular PWM or PFM operating modes.