Fully Integrated Digital Average Current-Mode Control Voltage Regulator Module IC

This paper introduces a fully integrated 12-to-1.xV voltage regulator module IC. A fully synthesizable digital two-loop controller has been realized through hardware description language tools. Several new IP blocks have been developed and described in detail: a window delay-line-based analog to digital converter (DL-ADC), two independent PI compensators with shared hardware for calculations, high-resolution digital pulsewidth modulation (PWM), and a programmable dead-time module. To fully exploit the benefits of digital electronics, reduce power consumption, and save area, all units of the digital controller have been designed through asynchronous architecture, eliminating the need of high-speed clock. High-performance synchronized, fixed frequency, PWM operation is enabled by a digital programmable time-base generator and system governor, which has been developed as well. In addition, to extend the capabilities of the window DL-ADC to support the full range of the load with minimal hardware penalty, adaptive reference of the current compensation is introduced. The mixed-signal IC has been fabricated on a 0.18- μm 5-V CMOS process. It incorporates the digital controller and periphery as well as a synchronous buck power stage, including a drive circuitry that enables operation up to several megahertz from a 12-V input. The digital core has been realized by an automated synthesis process and place-and-route tools, resulting in an effective silicon area of 0.16 mm². Experimental results of the fabricated IC operating in closed loop are provided, demonstrating the performance and benefits of the new controller for meeting the requirements of tight output voltage regulation over wide load range.