Wearable


Advances in low power microcontrollers and communication ICs have made it possible to build lightweight, unobtrusive, wearable smart devices that run diverse applications. Popular examples include smart watches and body signal monitoring bands.



Applications


Power and Battery Management

In a wearable device the power system must be able to regulate voltage from a battery—a voltage source with a declining voltage output. The regulators must be very efficient so as to maximize charge usage, and must also supply the number of rails required by the design. The usable voltage range of a rechargeable Li+ battery ranges from 4.2V to approximately 3.2V. Most wearable products use main power rails that are below the minimum charge of a single-cell Li+ battery, so the main rails within a wearable design are sourced from a step-down regulator. Some functions within a wearable product might require a higher voltage level than is provided by a single-cell battery. To provide these voltage levels the power management function must contain at least one step-up regulator. The number of rails required depends on the device functionality, but for optimum efficiency it’s best to minimize the number of required rails.

Wearable Healthcare Platform Design Considerations
PMICs for Wearables 
Boost Regulators for Wearables 
Battery Chargers for Wearables 
Battery Fuel Gauges for Wearables 

Processing

Power usage and processing capabilities are the most important selection criteria for a microcontroller for wearable applications. A system partitioning strategy should be used to decide which system functions are best integrated into the microcontroller and which can be handled externally. Because the wearable health devices read body signals, the capabilities of any on-chip analog circuitry must also be taken into account to ensure they can accurately process low-level body signals.

Wearable Healthcare Platform Design Considerations
High-Performance Microcontrollers for Wearables 

Sensors and Sensor Interface

The electrical outputs from body sensors have very low magnitude, in the millivolt and microvolt range. Accordingly, many of the sensors that are practical for wearable health applications have been combined with amplification and conversion circuits within a single die or package so that they output either a higher level analog signal or a serialized digital signal.

Wearable Healthcare Platform Design Considerations
Body Wearable Sensors 


Featured Products


Battery Management

Stand-Alone ModelGauge m5 Fuel Gauge with SHA-256 Authentication

MAX17201/5/11/15

This ultra-low power fuel gauge IC with SHA-256 authentication doesn’t require characterization, ideal for pack-side implementation.

Micropower 1-Cell/2-Cell Li+ ModelGauge ICs

MAX17048

Tiny, low-power fuel gauge maximizes battery run time and eliminates a current sense resistor.

USB/AC Adapter, Li+ Linear Battery Charger

MAX8606

This complete 1-cell Li+ battery charge-management IC operates from either a USB port or AC adapter. It integrates a battery disconnect switch, current-sense circuit, PMOS pass element, and thermal-regulation circuitry, while eliminating the external reverse-blocking Schottky diode, to create a simple and small charging solution.

Industry's Smallest 1.55A 1-Cell Li+ DC-DC Charger

MAX8971

This device charges quickly with minimal heat generation. It charges from variety of adapters and maximizes Safety featuring JEITA-compliant temperature monitoring and withstands transient inputs up to 22V.

Wearable Charge Management Solution

MAX14690

This battery-charge-management solution includes a linear battery charger with a smart power selector, several power-optimized peripherals and up to five regulated voltages, each with an ultra-low quiescent current in a 2.7mm x 2.5mm package.

ModelGauge m3 Fuel Gauge

MAX17047/MAX17050

These battery fuel gauges provide excellent short-term and long-term accuracy by using both coulomb counting and voltage-based ModelGauge algorithms. ModelGauge m3 cancels offset accumulation error in the coulomb counter while providing better short-term accuracy than any purely voltage-based fuel gauge.

 

Processors

High-Performance, Ultra-Low Power Cortex-M4F Microcontroller for Rechargeable Devices

MAX32620/1

These microcontrollers combines high-efficiency, signal-processing functionality with low cost, and ease of use. The device features 4 powerful & flexible power modes. Built-in dynamic clock gating and firmware controlled power gating minimize power consumption for any application. The MAX32621 incorporates a trust protection unit (TPU) with encryption and advanced security features.

Ultra-Low Power, High-Performance Cortex-M4F Microcontroller for Wearables

MAX32630/1

These are ARM® Cortex® -M4F 32-bit microcontrollers with a floating point unit, ideal for wearable applications. The architecture combines ultra-low power high-efficiency signal processing functionality with significantly reduced power consumption and ease of use. Both include a hardware AES engine. Further, the MAX32631 incorporates a trust protection unit (TPU) with encryption and advanced security features.

 

Sensors

Pulse Oximeter and Heart Rate Sensor for Wearables

MAX30102

This pulse oximetry and heart-rate monitor biosensor module includes internal LEDs, photodetectors, optical elements, and low-noise electronics with ambient light rejection for mobile and wearable devices.

 

DC-DC Regulators

28V Internal Switch LCD Bias Supply with True Shutdown

MAX1606

Boost converter uses internal switches to deliver up to 28V from inputs as low as 0.8V, with True Shutdown™.

30V Internal Switch LCD Bias Supply

MAX1605

Boost converter with 0.5A internal switch in a tiny 6-pin SOT23 package, accepts inputs as low as 0.8V.

Step-Up Converter for Handheld Applications

MAX8969

A simple 1A step-up converter in a tiny WLP package that can be used in any single-cell Li-ion application. This IC provides protection features such as input undervoltage lockout, short circuit, and overtemperature shutdown.


Solutions


For information about designing wearable health products, including example block diagrams of typical wearable products, please visit:

Wearable Healthcare Solutions

Related Resources



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November 2014



Body Temperature Measurement: Send and Receive With Wearable NFC
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Pulse Oximetry Measurement: Wearable Oxygen Monitor for Active Lifestyles
2:06 min
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