Digitally calibrated sawtooth generator for PWM based buck converters

An apparatus, comprising:

• a variable current source;
• a first capacitor coupled to the variable current source via a first node, the first capacitor is coupled to a discharge point via a first switch, and is to be charged by the variable current source when the first switch is opened, and to be discharged to the discharge point when the first switch is closed, to provide a sawtooth waveform at the first node;
• a first comparator coupled to the first node;
• a second capacitor coupled to the first node;
• a second comparator comprising an inverting input terminal coupled to the second capacitor, a non-inverting input terminal coupled to a selectable voltage, and an output terminal;
• and
• a switch coupled to the inverting input terminal of the second comparator and to the output terminal of the second comparator, the switch is closed when the first capacitor is discharged to the discharge point and open when the first capacitor is charged by the variable current source;
• wherein the variable current source is to adjust a respective output current in response to a sample of an output signal from the first comparator, and the second comparator is to generate a pulse-width modulated (PWM) waveform on its output terminal based on a comparison between a voltage of its inverting input terminal and the selectable voltage of its non-inverting input terminal.