Patent ID: 7482791
Filing Date: 2009-01-27
Classification: H02M

Abstract:
1. A buck switching regulator formed on an integrated circuit and receiving an input voltage, the buck switching regulator controlling a first switch and a second switch using a constant on-time, variable off-time feedback control loop to drive a switch output node for generating a switching output voltage, the switch output node being coupled to an LC filter circuit external to the integrated circuit to generate a regulated output voltage having a substantially constant magnitude on an output node, the regulated output voltage being fed back to the buck switching regulator to a voltage divider for generating a feedback voltage on a feedback voltage node, the buck switching regulator comprising: an amplifier with a high output impedance having a first input terminal coupled to receive the feedback voltage, a second input terminal coupled to receive a first reference voltage and an output terminal providing a first output voltage indicative of the difference between the feedback voltage and the first reference voltage; an error comparator having a first input terminal coupled to receive a second reference voltage and a second input terminal coupled to receive the first output voltage of the amplifier, the error comparator generating an output voltage signal for controlling the constant on-time, variable off-time feedback control loop of the buck switching regulator; a first capacitor and a first resistor formed on the integrated circuit of the buck switching regulator, the first capacitor and the first resistor being connected in series between the switch output node and the output terminal of the amplifier; and a second capacitor coupled between the output node and the output terminal of the amplifier, wherein the first capacitor and the first resistor generate a ripple voltage signal being related to the switching output voltage and provide the ripple voltage signal to the output terminal of the amplifier for use in the constant on-time, variable off-time feedback control loop, the magnitude of the ripple voltage signal being a function of the capacitance value of the second capacitor.