A Single-Inductor-Multiple-Output (SIMO) 0.8-V/1.8-V/12-V Step-Up/Down Converter With Low-Quiescent Current for Implantable Electroceutical SoCs

Abstract

This letter presents a single-inductor-multiple-output (SIMO) step-up/down dc-dc converter for an implantable electroceutical system on chip (SoC), which generates the supply voltages of 0.8, 1.8, and 12 V from a battery (3-4.2 V). To extend the battery lifetime during a long standby period, the load-adaptive frequency-scaling (LAFS) without an active load sensor is proposed, effectively reducing the quiescent current under light loads at no expense of transient response performance. Also, this letter introduces a new design of a low-power adaptive on-time (AOT) generator to achieve a consistently low-output ripple regardless of battery voltage variation. The proposed chip fabricated in 0.18-mu m BCD consumes a quiescent current of only 217 nA and offers the output recovery time of <= 1 ms at a zero-to-full load transition. The measured efficiency was 86% with a load of 500 mu A and 55% even with an ultra-light load of 1 mu A.