MAXREFDES220: Reference Designs for Finger-Based Heart Rate and Pulse Oximetry Product Prototyping

MAXREFDES220 wearable heart monitor

Wearable health products like the MAXREFDES220 are very popular and easy to design with the right set of components

If you’re getting started on a design in a new application area or you’re developing an innovative new product, the design process will be easier if you have resources to help you get started. Wearable health monitoring products are becoming increasingly popular and there are many components on the market to support these designs. To properly design these marketable products, designers need access to a set of integrated sensors and a processing platform that automates signal readout and processing.

Heart rate monitoring and pulse oximetry are two standard features on any personal health monitor, and the MAXREFDES220 reference design from Maxim Integrated is one resource designers have to develop new products with these important features. While personal health monitors may seem like they should be relatively complex products, they really only rely on a few key components. The MAXREFDES220 can show you how to start using these primary components to build out a personal health monitor or a more complex medical device.

Heart Rate and Pulse Oximetry with the MAXREFDES220

The MAXREFDES220 is a personal health monitor that provides integrated heart rate monitoring, pulse oximetry, and step counting on a single platform. The product is built on top of the MAX32630FTHR, a microcontroller evaluation board that supports a diverse array of applications. The MAXREFDES220 is not a ready-to-wear fitness monitor like the MAXREFDES103, but the additional processing capabilities of the MAX32630FTHR host controller allow designers to build an application around the core components on the MAXREFDES220.

The MAXREFDES220 is built around a few particular components:

    • MAX30101: This IC is an integrated, high-sensitivity pulse oximeter and heart rate sensor. This component meets FDA Class II Device accuracy requirements, although your end product may have a different accuracy level and should be qualified by the FDA.
    • MAX32664: This component is an integrated sensor readout and processing IC that easily interfaces with a variety of Maxim Integrated biometric sensors.
    • BMI160 3-axis Accelerometer: Using an accelerometer allows this product to be used to track heart rate and SpO2 levels during exercise or while walking.
    • MAX32630FTHR: This evaluation board contains the main MCU (MAX32630IWG+) used to build an application around the other two components. The MAX32630FTHR can also be used to communicate with other MAX32664 biometric sensor interfaces to build a larger health monitoring product.

MAXREFDES220 block diagram

Block diagram of the MAXREFDES220 from the MAXREFDES220 product page

In the block diagram above, the MAX32630FTHR acts as a baseboard for the MAX30101 and MAX32664 components. It provides all the important processing and application functions in the product, which are implemented on the MAX32630IWG+ MCU. These components are branded as low-power components and can provide long battery life. Power management of the MAX32664 and MAX 30101 components can also be implemented with the MAX32630IWG+, all of which can be put into sleep mode with ultra-low current draw.

It’s important to note that the MAXREFDES220 is not a completed, wearable product, but it can be quickly used as a functional prototype for testing a real application. This product is built on Maxim Integrated’s MAX32630FTHR application development platform, which makes it easy to develop, test, and debug a proof-of-concept application before flashing it onto a functional prototype for more rigorous testing. Thanks to some design resources for the MAX32630FTHR baseboard, firmware developers can build production-grade applications around the MAX30101 and MAX32664.

Design Resources for MAX Health Monitors

The MAXREFDES220 platform is not in a state where it can be tested in the field as a health monitor product, but it is excellent for application development. Designers who want to use the MAXREFDES220 as a baseline for their new product will need to write custom firmware for the application and use additional components to build their product.


Maxim Integrated designs with multiple digital components and an MCU will need some custom firmware to integrate features from each component into a larger application. Specifically, developers will need to write firmware for the MAX32664 component, as this part will handle the collection and processing of data from the sensor. Code libraries and other resources for firmware development can be found on the MAX32664 product page.

Other Components for Health Monitor Design

When you’re ready to design a custom PCB for a health tracker, you’ll need other components in addition to MAX30101 and MAX32664. Some components in these designs include:

  • USB connector: Today’s mobile devices and wearables are all charged via USB, so you’ll need a USB Type-C connector so your design can plug into a standard charger. 
  • Power regulator and battery charge controller: Battery-powered units need a small battery charge controller and power regulator (usually an LDO) to ensure stable power and long battery life. 
  • Bluetooth or Wifi transceiver: Health monitor devices often connect to a phone via Bluetooth or Wifi at 2.4 or 5 GHz. If you don’t want to use the MAX32630IWG+ MCU, there are other MCUs that include an integrated BLE transceiver and will support the MAX32664 firmware. 
  • Display: If you don’t want the user to do everything through an app, then you’ll need a display for your design. These screens are usually moderate resolution OLED touch screens. 

When you use the right electronics search engine, it’s easy to find reference designs from Maxim Integrated and other major component manufacturers. Searching by application helps you find designs from multiple vendors or by specific manufacturers. This is a great option if you still need to find components for your product.

 Electronics reference design Maxim Integrated

Example reference designs from Maxim Integrated

Whether you need to find electronics reference designs like the MAXREFDES220 or individual components, try using the electronics search engine features in Ultra Librarian. When you use Ultra Librarian, you’ll have access to datasheets, technical specifications, CAD data, and verified 3D models that can be imported into popular ECAD applications. Ultra Librarian has also partnered with major component manufacturers like Maxim Integrated and Cadence, to make their reference designs easily searchable and available in Cadence systems formats.

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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