Revolutionizing power management for wearable power management with SIMO technology
Wearable and IoT devices are becoming increasingly compact and feature-rich. As consumers demand slimmer smartwatches, more comfortable fitness trackers, and barely visible wearables, the power management puzzle becomes increasingly complex.
Have you ever wondered how your fitness tracker manages to run for days on such a tiny battery? Or why your wireless earbuds seem to get smaller yet more powerful with each generation? The smaller the device, the less room for batteries, yet users still expect their devices to last all day or longer. The problem is physics: smaller devices mean smaller batteries and typically shorter battery life. It is the frustrating triangle of wearable design that engineers have been fighting for years. The MAX77650 and MAX77651 from Analog Devices address these issues with Single-Inductor Multiple-Output (SIMO) technology and redefine power management for wearables and ultra-portable devices.
What makes the MAX77650/51revolutionary?
Traditional Power Management ICs (PMICs) for wearables face challenges such as inefficient power conversion, limited battery life, and space constraints. Many wearables require multiple regulators, which increase board size, component count, and power losses. Existing solutions often fail to balance high efficiency with compact designs, making it difficult for engineers to optimise power budgets in modern wearables.
Here, Analog Devices' innovative solution is introduced: the MAX77650/51 power management ICs. They reduce the PCB footprint through a single-chip SIMO architecture while improving power efficiency, extending battery life with ultra-low quiescent current operation, and simplifying system design with an integrated solution. The next-generation SIMO PMIC reduces component count by up to 40% and BoM cost by 23%, making it ideal for compact consumer devices like wearables and hearables. It delivers three outputs at 91% efficiency using a single inductor, replacing three traditional converters and inductors in a 19mm² solution that’s 50% smaller. The PMIC improves battery life by 20%, reduces heat dissipation by 7x, and lowers board temperature by over 20°C. It operates with a 500nA shutdown current and 6µA supply current (with five regulators on). It maintains low output ripple under 20mVp-p—ideal for noise-sensitive applications like GPS, biometric sensors, gesture control, 3D recognition, and compact cameras. Think of it as the difference between having three separate water pumps for your house (wasteful and space-consuming) versus one smart pump that efficiently directs water exactly where and when it's needed. That's essentially what SIMO does for power in your wearables!
Figure 1: Simplified application circuit of the MAX77650
Figure 1 shows a simplified application circuit of the MAX77650 PMIC, which manages power from sources like USB and batteries to supply multiple regulated voltages (1.2 V, 2.05 V, 3.3 V, 1.85 V) to system resources and a processor while also supporting LED drivers, GPIOs, I²C communication, and battery charging.
Key features and unique selling points
Here are the standout features that make the MAX77650/51 special:
- Design simplicity and integration: The SIMO Buck-Boost regulator generates three independent voltage rails from a single inductor. A 150mA LDO provides ripple rejection for noise-sensitive applications like audio, ensuring clean power delivery.
- Power efficiency and battery life: It offers ultra-low power consumption, with 0.3 µA in shutdown and 5.6 µA operating current, extending battery life in low-power modes. This is vital for always-on devices, unlike those powered by other PMICs that may have higher quiescent currents.
- Space and size challenges: The MAX77650/51 uses a single inductor for multiple outputs, reducing the footprint by up to 50%, - crucial for small devices like smartwatches and fitness trackers.
- Safety and flexibility: Highly configurable for Li-ion batteries, with JEITA-compliant temperature monitoring for safety. It also includes current sinks for LED indicators, an analog multiplexer for monitoring, and an I²C interface for configuration and status checking.
Figure 2: MAX77650EVKIT top view
Figure 2 shows the MAX77650/MAX77651 Evaluation Kit, which provides a complete platform to test and evaluate the PMIC's features such as power rails, LED drivers, charger functions, I²C communication, and GPIO control, using labeled test points, headers, and a USB interface for GUI connection.
Applications in smart wearables
The MAX77650/51 is ideal for battery-powered, space-constrained devices such as:
- True wireless earbuds (TWS) and hearables
- Smartwatches and fitness bands
- Medical wearables (continuous glucose monitors, ECG monitors)
- IoT sensor nodes and ultra-portable gadgets
So, next time you wonder how your tiny fitness tracker lasts all week or how your wireless earbuds pack so much tech into such a small package, remember—there's probably some clever SIMO technology making that magic happen!
