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 electro-ceutical system-on-chip (SoC), which generates the supply voltages of 0.8 V, 1.8 V, and 12 V from a battery (3 -4.2 V). To extend the battery life-time 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 tran-sient response performance. Also, this paper introduces a new design of a low-power adaptive on-time (AOT) generator to achieve a consist-ently low output ripple regardless of battery voltage variation. The proposed chip fabricated in 0.18-mum BCD consumes a quiescent cur-rent 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 muA and 55% even with an ultra-light load of 1 muA.