14.4 A Monolithic 26A/mm2Imax, 88.5% Peak-Efficiency Continuously Scalable Conversion-Ratio Switched-Capacitor DC-DC Converter

As SoC complexity continues to increase, more and more fine-grained power domains are being employed to more precisely allocate power and meet stringent requirements on power, performance, and battery life. This does, however, put additional strain on the power delivery system as each time a domain is divided into multiple domains, the sum of the maximum currents that must be supported increases beyond the current rating of the initial domain. For voltage regulators (VRs), this has proven particularly troublesome. Switched-inductor buck or resonant converters rely on large on-board or in-package inductors [1], limiting the number of possible power domains and incurring large volume overheads as current rating increases. Low-Dropout (LDO) regulators, in contrast, do not rely on large passives and can be scaled more easily to fit the domain demands, but have poor efficiency if the various load domains have widely different voltage requirements or rely on aggressive dynamic voltage and frequency scaling (DVFS). Switched-Capacitor Voltage Regulators (SCVRs) offer the promise of providing scalable voltage conversion without having to rely on in-package components but have so far not lived up to their expectations. Conventional SCVR topologies have demonstrated both high current density and efficiency thanks to the use of high-density on-die capacitors [2] or using an approach where MIM capacitors are placed on top of the load domain while minimizing the active silicon area of the converter- and thus cost [3]. But because they do not maintain high efficiency across a wide voltage range, they have some of the same drawbacks as LD0s. The Continuous-Scalable Conversion-Ratio (CSCR) topology [4], on the other hand, can maintain high efficiency across voltage conversion ratios (VCRs) but has never been demonstrated with high current density [5]. In this work, a Phase-Merging-Turbo (PMT) technique is proposed that can significantly increase the current capability of CSCR SCVRs.