High‑Performance PMICs Power Always‑On Wearables and IoT Devices

Designing a wearable that stays on the go requires a blend of compact form, sleek aesthetics, and, most critically, power efficiency. To meet these demands, engineers focus on tiny, highly integrated power‑management ICs (PMICs) that extend battery life while keeping the device lightweight and comfortable. These ICs enable continuous operation, smooth data collection, and reliable connectivity—key for wearables that track health metrics or connect to the Internet of Things (IoT).

Optical‑sensing accuracy, a cornerstone of many health wearables, depends heavily on the underlying power architecture. Ultra‑low‑power PMICs are engineered to minimize noise and optimize voltage regulation, thereby enhancing the sensitivity of photoplethysmography (PPG) and other optical measurements. In wrist‑worn form factors, this translates to more precise vital‑sign readings, even during movement or varying ambient light conditions.

Over the past decade, the number of wearable sensors has surged, driven by rising healthcare costs, the growth of “health fanatics,” and the proliferation of online health data. As consumer expectations for instant, actionable insights grow, so does the need for reliable electronics that can sustain higher power demands—especially for advanced functions like speech recognition, gesture control, and continuous monitoring.

Traditional lithium‑ion (Li‑ion) cells still serve low‑power wearables, but they struggle to meet the power density required by high‑performance devices. The industry is therefore moving toward smaller, thinner packages and the next generation of integrated power‑management circuits that support rapid charging, efficient voltage conversion, and comprehensive safety monitoring.

PCB design for wearables must balance material selection with electromagnetic compatibility (EMC) requirements. Tight impedance control and meticulous trace routing are essential to ensure clean signal propagation, reduce interference, and maintain overall device integrity.

PMIC Architecture

A typical wearable architecture integrates a system‑on‑chip (SoC), memory, display, sensors, and power‑management blocks. The power system usually includes a charger, buck converters, and low‑dropout regulators (LDOs) to supply Bluetooth or Wi‑Fi modules. Key design challenges involve thermal dissipation and battery sizing, both of which hinge on selecting the right PMIC.

Most systems require a charger and multiple regulated outputs—for example, 3.3‑V and 1.2‑V supply buses for the microcontroller and communication interfaces. A highly configurable linear load within the PMIC supports a broad range of Li‑ion chemistries and includes battery temperature monitoring for added safety. A bidirectional I²C interface allows designers to configure and monitor device status, while an integrated supervisor ensures reliable operation.

Switching regulators (buck and boost) deliver the highest efficiency, whereas low‑voltage LDOs are preferred for low‑noise applications. An optimal supply chain often relies exclusively on switching supplies, but each switch demands an inductor, which can inflate PCB area and device thickness.

To reconcile these constraints, many designs adopt a single‑input, multiple‑output (SIMO) architecture that consolidates several power buses into one IC. SIMO PMICs provide multiple regulated rails while keeping standby current low, extending battery life and trimming the bill of materials by eliminating redundant components.

For example, Maxim Integrated’s MAX20310 integrates two SIMO buck‑boost outputs, two LDOs, and a sequencing controller. Its linear regulators can double as power switches, disconnecting inactive peripherals to improve overall efficiency (see Fig. 1).

Fig 1: A block diagram of the MAX20310. (Image: Maxim Integrated)