Samsung Advanced Institute of Technology

This paper presents a single-inductor multiple-output (SIMO) step-up/down converter integrated into the implantable electroceutical system-on-chip (SoC), which generates the internal supply voltages of 0.8 V, 1.8 V, and 12 V from the battery (3 ？ 4.2 V). To extend battery time during a long standby period, the low-powered circuits suitable for a pulse skipping scheme are proposed. The load-adaptive frequency scaling (LAFS) technique without using an active load sensor is proposed, effectively reducing the quiescent current under light loads at no expense of transient response performance. Also, this paper introduces a new design of low-power adaptive on-time (AOT) generator to achieve the consistent low output ripple regardless of battery voltage variation. The proposed chip fabricated in 0.18-μm BCD process 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％ at a load of 500 μA, and 55％ even at an ultra-light load of 1 μA.