Apparatus and method for step-down switching voltage regulation

A circuit for switched buck regulation, comprising:

• an inductor circuit that is coupled between a switch node and an output node;
• a capacitor circuit that is coupled to the output node;
• a bottom-side switch circuit that is coupled between a ground node and the switch node;
• a top-side switch circuit that is coupled between switch node and an input node;
• a current sense amplifier circuit including a first input that is coupled to the switch node, and further including a second input that is coupled to the ground node;
• a sample-and-hold circuit including an input that is coupled to an output of the current sense amplifier circuit;
• an oscillator circuit;
• a current source circuit including a first input that is coupled to the output node and a second input that is coupled to a resistor, wherein the resistor is coupled to the input node;
• an analog current multiplier circuit including a first input that is coupled to an output of the oscillator and a second input that is coupled to an output of the current source circuit;
• a ramp generator circuit including a first input that is coupled to an output of the analog current multiplier circuit and a second input that is coupled to an output of the sample-and-hold circuit;
• and
• a switch control circuit including an input that is coupled to an output of the ramp generator circuit.

A method for providing switched buck regulation, comprising:

• providing a ramping current;
• providing an output voltage from the ramping current;
• coupling a ground node to the means for providing the ramping current if a first switch control signal is asserted;
• coupling an input node to the means for providing the ramping current if a second switch control signal is asserted;
• sensing a current across the means for coupling the ground node to the means for providing the ramping current;
• providing a current sense voltage in response to the current;
• sampling the current sense voltage if the means for providing the ramping current is coupled to the ground node;
• holding the current sense voltage if the means for providing the ramping current is coupled to the input node;
• providing an oscillator current;
• providing a source current based in part on a difference between the output voltage and a predetermined portion of the input voltage;
• providing a control current based in part on the source current and the oscillator current;
• providing a ramp voltage based in part on the control current and sampled-and-held current sense voltage;
• and
• providing the first and the second switch control signals based on the ramp voltage.