Design Considerations of Distributed and Centralized Switched-Capacitor Converters for Power Supply On-Chip

On-chip power supply distribution faces the challenges of high and fast-changing load current, limited metal layers and decoupling capacitors, efficiency, and thermal issues. This paper mainly discusses system-level design considerations of both distributed and centralized fully integrated voltage regulators. In particular, a ring-shaped switched-capacitor dc-dc converter that has a unity-gain frequency a few times higher than its switching frequency is introduced with comprehensive considerations, and optimizing the number of time-interleaving phases (power cells) is detailed. Design issues such as on-chip power-rail routing parasitics, input capacitor and input ripple, and phase mismatch between power cells are addressed. Furthermore, a couple of possible extensions of the converter-ring architecture are proposed, which include power management of the active-matrix light-emitting diode array in a microdisplay system, cascading multiple nMOS-LDO regulators for granular power, and on-chip power converter grid with flipped-chip packaging.