Switched-Capacitor DC–DC in Bulk CMOS for On-Chip Power Granularization

Abstract

Recent trends show that the power management unit (PMU) to supply System-on-Chip solutions is undergoing a transformation and is taking a leap toward monolithic integration [31, 39, 130]. This is a necessary evolution because of multiple market requirements. On the one hand, modern electronic systems are forced to be more energy efficient. This can follow from constraints on heat dissipation, where lower losses result in a lower overall dissipated heat, or to increase the battery autonomy in mobile systems. On the other hand, monolithic integration enables to reduce the form factor of power converters, saving on the required PCB board space. On top of that, the solution thickness can be reduced [122], which has become an important differentiation in modern high-end smartphones. In order to improve system efficiency and form factor reduction, these systems frequently rely on energy saving techniques, such as Adaptive Voltage Scaling (AVS), Dynamic Voltage Scaling (DVS), Dynamic Frequency Scaling (DFS), power and clock gating to realize (deep, etc.) sleep, multiple supply voltages with voltage islands and power domains, and so on. Consequently, the step toward integrated power conversion is a key enabler for the aforementioned techniques because it allows power delivery to take place via a distributed or granular concept, yielding the possibility of many voltage domains. In fact, once power converters are integrated on chip, the concept of having one centralized power converter becomes obsolete. There is no longer a reason to keep the power converter in one place besides tradition, which is not a rational motivation and leads to bad circuit design [30].