17.7 A 0.03mV/mA Low Crosstalk and 185nA Ultra-Low-Quiescent Single-Inductor Multiple-Output Converter Assisted by 5-Input Operational Amplifier for 94.3% Peak Efficiency and 3.0W Driving Capability

Abstract

The single-inductor multi-output (SIMO) converter offers the advantage of small size and can provide distributive voltage/current for wearable electronic devices. However, there are still some design challenges to solve. In continuous-conduction-mode (CCM) control, it is difficult to reduce crosstalk between multiple outputs [1– 5]. Any crosstalk will result in excessive or insufficient energy in other outputs, resulting in severe voltage ripple. In the upper left of Fig. 17.7.1, when there is any load change on $\mathrm{V}_{O2}$, crosstalk will occur at $\mathrm{V}_{O1}$ and $\mathrm{V}_{O4}$. On the other hand, in the discontinuous-conduction-mode (DCM) control [6, 7], if any one of the multiple outputs changes from light load to heavy load, serious crosstalk occurs due to the extension of the switching period $\mathrm{T}_{SW}$, as shown in the upper right of Fig. 17.7.1. Although constant frequency control can avoid the expansion of $\mathrm{T}_{SW}$ [8], the limited peak inductor current will reduce the driving capability $(\mathrm{I}_{LOAD(MAX)} \quad =100$ mA [8]). In this paper, the proposed SIMO converter, shown at the bottom left of Fig. 17.7.1, uses an adaptive switchable CCM and DCM (ASCD) technique that takes advantage of the high driving capability of CCM and the advantage of reducing crosstalk in DCM under light loads. To effectively reduce the crosstalk in CCM (Mode1 in this paper), a 5-input crosstalk-reduction error amplifier (CREA) with a feedback rotator is proposed to reduce the shortcomings of hardware overhead in [1– 10]. For achieving low crosstalk and high driving capability under medium load, the SIMO converter works in a combination of stacked DCM and sequential DCM, which are classified as Mode2 to Mode4 to change the energy distribution path of each output (Fig. 17.7.1 bottom right). Under ultra-light load conditions, the switching cycle $\mathrm{T}_{SW}$ can be extended to reduce switching power loss, and SIMO will enter the ultra-low-power (ULP) mode (Mode5) to further reduce the quiescent current and increase the battery runtime.