Fitness Tracker Design with the MAXREFDES103

fitness tracker design graphic

Use the MAXREFDES103 to get started with fitness tracker design

Sometimes, a designer needs to pivot into a new application area and start designing unfamiliar systems. As fitness trackers grow in popularity, you might find yourself wanting to try your hand at designing these in-demand wearables. 

Fitness trackers are small devices involving multiple microelectronic sensors and a central processor that must synthesize a wealth of health information in a tiny package. They also have a particular form factor to which users have become accustomed to and new designs will have to fit into this form factor.

If you’re planning a new fitness tracker design, but you’ve never worked in this area before, the MAXREFDES103 Health Sensor reference design can help you design a new health tracker product. It contains PPG algorithms that include power optimization, pulse rate/heart rate, interbeat interval, heart rate variability, stress monitoring, sleep quality monitoring, respiration rate monitoring, and VO 2 Max. All this offers users a complete evaluation and design guidance platform. 

This reference design is also unique from many other designs in that it includes a real wristband containing the reference board. You can use this product and many others as examples for your next design or you can use it as a development tool to debug software/firmware for your prototype.

Starting a Fitness Tracker Design

Fitness trackers operate on a simple concept: gather vital signs from the wearer and display them in an embedded screen or send data to a mobile app. Every fitness tracker needs a few essential components to provide these basic functions:

  • Microcontroller (MCU): The MCU will control all the important functions, including data collection and processing. The MCU needs to interface with other functional blocks in the system and send data back to the user for viewing. It may also need to accept input from the user, either via a touch screen or a mobile app.
  • Sensors: Most fitness trackers include a pulse oximeter, heart rate monitor, and temperature sensors, as well as an accelerometer to track footsteps and speed. More advanced sensors are present in specialty health trackers and medical products which may not be used strictly for fitness and exercise. 
  • Analog front-end (AFE): The AFE section includes multiple filters and amplifiers that are needed to collect and clean up analog signals from the sensors. 
  • Rechargeable battery and charge controller: Fitness trackers are small devices, and they need to include a small battery charge controller and power regulator to ensure long battery life. Rechargeable Li-ion batteries are standard for fitness trackers. 
  • Bluetooth transceiver: Fitness trackers connect to other mobile devices via Bluetooth at either 2.4 GHz or 5 GHz. Some MCUs, like the nRF52 series from Nordic, will include an integrated BLE transceiver, making them ideal for the small form factor of a wearable fitness tracker design. 
  • Display: Not all fitness tracker designs have a display, but this is a nice add-on that lets the user view their health information without requiring an app. These screens are usually moderate resolution OLED touch screens. 

The key to getting to a small form factor is to take advantage of components that integrate multiple functions into a single package. Maxim Integrated now offers products that integrate these functions into a small set of components. A great way to get started using these components and building an app that will interface with your system is to use the MAXREFDES103 reference design.

What’s in the MAXREFDES103 Health Tracker?

The MAXREFDES103 from Maxim Integrated is more than just a development board—it’s a reference fitness tracker design that comes complete with a wristband and software support. The goal is to provide developers a reference design that gives the required electrical functionality as well as wearer functionality so that wearers can evaluate all aspects of a new product.

Maxim Integrated MAXREFDES103

The MAXREFDES103 reference fitness tracker design from Maxim Integrated

This reference design is built around two primary components that provide most of the fitness tracker design functions:

  • MAX32664: This product is a highly integrated health tracker MCU providing communication with multiple biometric sensors from Maxim Integrated. This component runs with a lightweight Arm Cortex-M4F core with 32-bit processing for highly accurate signal acquisition and processing.
  • MAX86141: This component is an integrated pulse oximeter and heart rate sensor. Data is provided back to the MAX32664 via SPI, so no external ADC is needed to process sensor signals into digital data.

Other components include a Bluetooth transceiver, temperature sensor, and MAX4740 quad SPDT switch for interfacing with all onboard sensors. You can view the full BOM and find CAD files on the MAXREFDES103 product page. If you want to build a new design around these core components or add new features to the MAXREFDES103, you can find the components and CAD models you need with a parts search engine.

Use an Electronics Search Engine to Find Reference Designs

The MAXREFDES103 is one of many Maxim Integrated reference designs targeting the healthcare industry with personal medical products. Many other component manufacturers provide a range of reference designs targeting different applications. All of these reference designs are a great place to start if you’re designing products for an industry that might be unfamiliar. For products supporting embedded systems, reference designs generally come with plenty of manufacturer development support, and you’ll likely be able to find example projects from the open-source community.

If you’re looking for development products for specific applications, use a comprehensive electronics search engine to find reference designs and evaluation boards. The best search engines will let you search by application, part type, or part number to find the development product you need. Just like Maxim’s MAXREFDES series, many developer products are branded and can be found from major electronics distributors.

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Search for parts with Ultra Librarian’s electronics search engine

If you’re looking for reference designs for new products, or if you need to find MCUs and sensors for fitness tracker design, try using the electronics search engine features in Ultra Librarian. In addition to component data, you’ll have access to verified component models that can be imported into popular ECAD applications. Thanks to a partnership between Maxim, Cadence, and Ultra Librarian, all Maxim Integrated reference designs in Ultra Librarian can be downloaded in Cadence systems formats and used to create your new product.

Working with Ultra Librarian sets up your team for success to ensure any design is going through production and validation with accurate models and footprints to work from. Register today for free.


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