Advanced Control Features of Hybrid Current-Programmed Digital Controller in Multiphase VRM Applications

This paper introduces advanced digital control features intended for high-end multiphase VRM controllers. These features are incorporated in state-of- the-art digital hybrid Average Current Mode (ACM) control architecture to facilitate a through and comprehensive solution required in voltage regulation of high-performance loads. Particularly, two main architectures are detailed. A phase shedding (and adding) scheme to determine the optimal phase-count according to the per-phase maximum efficiency region and the current provided to the load, and an Active Voltage Positioning (AVP) modifies the output voltage to limit instantaneous heat dissipation of the load according to a programmable piecewise linear load-line profile. In addition, the voltage regulation scheme is based on a control scheme that hybrids two control laws: a linear ACM and non-linear acceleration for optimized transient response. The hand-off procedure, presented in this study, achieves seamless transitioning between controller operations, reducing post-transient output voltage deviations and current spikes. The mixed-signal platform (digital controller, analog interfaces, acquisition periphery) have been tested and successfully validated experimentally on Intel-certified hardware and test protocols. The experimental prototype features a 4-phase 12V to 1.xV multiphase buck VRM that drives an array of 7 DDR4 load modules, accommodating 100A load transients with transition rate of 2000A/us, demonstrating minimum-deviation load recovery as well as ace steady-state target tracking.