COVER STORY Delivering long battery life in tiny devices
Introducing ‘SIMO’ Single Inductor Multiple Output power architecture solutions from Analog Devices
When you wear your earbuds for a long hike or an afternoon at the gym, you don’t want to be interrupted by having to stop and recharge the earpieces. You expect your hearables, wearables, and other tiny, battery powered electronic devices to perform reliably over long periods of time. From a design standpoint, these user expectations are a tall order to meet. The form factor
constraints dictate the need for a small Lithium-Ion battery, which must last a long time between charge cycles and be utilized sparingly. Power supplies, in turn, must meet the distinct and diverse voltage requirements of the sub-systems within the design. The SIMO architecture provides an optimal solution for these systems, integrating functionality that would otherwise require multiple discrete components. In this month’s issue Kevin Doyle, field applications engineer at Anglia, gives an insight into what a SIMO architecture is and how it works for buck-boost regulators.
SIMO regulators
Single Inductor Multiple Output (SIMO) ICs harness the high efficiency of switching converters with the compact, space saving architecture of a single inductor design for multipower rails applications. Analog Devices’ family of single inductor multiple outputs (SIMO) power management ICs provides multiple switching buck-boost regulators using only one single inductor. The high efficiency conversions benefit and extend battery life, while the ultracompact size and low bill of materials provide a perfect solution for space constrained wearables, hearables, IoT and other small form factor battery powered industrial, eHealth and consumer devices. Additional integrated functionalities and features further simplify the design of low power portable devices by incorporating functions such as battery management (charger and fuel gauging), LDO outputs for noise-sensitive rails and on- board sequencing for controlled power-up and power-down. Additionally, an I2C interface provides the capability to enable complete customization of the power management IC and supports dynamic voltage scaling (DVS) for additional power savings and custom power profiles.
SIMO architecture
In a traditional multiple switching regulator topology, each switching regulator needs a separate inductor (Figure 1). The inductors can be physically large and costly, this is a major disadvantage for small form factor products. The other option is to use linear regulators, which are fast, compact, and low noise, but have higher power dissipation. There’s also the hybrid alternative of using multiple low-dropout regulators (LDOs), in conjunction with DC-DC converters. However, while this configuration would result in intermediate power and heat dissipation, it still yields a larger design than LDOs alone. The featured buck-boost SIMO converter can regulate up to three (four on the MAX77655) output voltages over wide
10 March 2023 Components in Electronics
www.cieonline.co.uk
Figure 1: Traditional architecture for buck-boost switching regulator and the MAX77643 SIMO
output voltage ranges using a single inductor. The buck-boost topology helps to better utilize the inductor since it requires less time to service each channel compared to a buck-only SIMO.
A buck-only SIMO will suffer when an output voltage approaches the input battery voltage. Presently, a buck-only
SIMO requires the inductor for too much time, which impacts the other output channels. The topology of the SIMO buck- boost is outlined in Figure 2.
Note: the flow arrows are illustrative only and do not represent current flow at any specific time.
As shown in Figure 2, under the control of the “Service On
Figure 2: SIMO architecture
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