A Low Power High Resolution Digital PWM with Process and Temperature Calibration for Digital Controlled DC-DC Converters

Research Category: Engineering and Technology
Presenter: Ho Joon Lee
PI: Yong-Bin Kim

In this paper, a 12-bit high resolution, power and area efficiency hybrid digital pulse width modulator (DPWM) with process and temperature (PT) calibration is proposed for digital controlled DC-DC converters. The hybrid structure of DPWM combines a 6-bit differential tapped delay line ring-mux digital-to-time converter (DTC) schema and a 6-bit counter-comparator DTC schema, resulting in a power and area saving solution. Furthermore, the 6-bit differential delay line ring oscillator serves as the clock to the high 6-bit counter-comparator DTC, thus a high frequency clock is eliminated and power is significantly saved. In order to have simple delay cell and  flexible delay time controllability, voltage controlled inverter is adopted to build the deferential delay cell, which allows fine-tuning of the delay time. The PT calibration circuit is composed of process and temperature monitors, two 2-bit flash ADCs and a look-up table. The monitor circuits sense the PT (Process and Temperature) variations, and the flash ADC converts the data into digital code. The look-up table combines both the process and the temperature digital information, and provides an appropriate value to the control voltage of the differential delay cell. The complete circuits design has been verified under different corners of CMOS 0.18um process technology node.