A 30-MHz Voltage-Mode Buck Converter Using Delay-Line-Based PWM Control

A 30-MHz voltage-mode buck converter using a delay-line-based pulse-width-modulation controller is proposed in this brief. Two voltage-to-delay cells are used to convert the voltage difference to delay-time difference. A charge pump is used to charge or discharge the loop filter, depending on whether the feedback voltage is larger or smaller than the reference voltage. A delay-line-based voltage-to-duty-cycle (V2D) controller is used to replace the classical ramp-comparator-based V2D controller to achieve wide duty cycle. A type-II compensator is implemented in this design with a capacitor and resistor in the loop filter. The prototype buck converter was fabricated using a 0.18-mu m CMOS process. It occupies an active area of 0.834 mm(2) including the testing PADs. The tunable duty cycle ranges from 11.9%-86.3%, corresponding to 0.4 V-2.8 V output voltage with 3.3 V input. With a step of 400 mA in the load current, the settling time is around 3 mu s. The peak efficiency is as high as 90.2% with 2.4 V output and the maximum load current is 800 mA.