Behind the Scenes: Ultra-Small Wearable Healthcare Design Platform

Behind the Scenes: Ultra-Small Wearable Healthcare Design Platform

There’s nothing new about wearable healthcare electronics, given that devices like hearing aids and pacemakers have been around for years. What’s novel, of course, is all of the data being generated, along with the connectivity that allows this information to be shared. Developing products that are small, unobtrusive, connected, and data-centric is no easy feat.

“There’s a lot of innovation happening now in the wearable healthcare space,” says Sudhir Mulpuru, executive business manager in Maxim’s Industrial and Healthcare Business Unit. “Everybody has a different idea of what might work, or what might provide meaningful information about human physiology. There are things that have never been tried before.”

To help designers test out new assumptions and quickly move from concept to prototype to product, Maxim offers its hSensor Platform, otherwise known as the MAXREFDES100# reference design. The platform can shave up to six months off the product development cycle for a variety of wearable clinical and fitness applications.

“We wanted to make this really small wearable platform that could be a complete reference design for specific use cases,” explained John DiCristina, a distinguished member of the technical staff for product definition at Maxim. “We wanted to include a variety of sensors—such as contact temperature, ECG, heart rate, and barometric pressure—and have the platform be adaptable for using one or more of the sensors.”

Easing the Design Process for the Internet of Medical Things

Mulpuru and DiCristina are part of the team that developed the hSensor Platform. Fitting all of this functionality in a tiny form factor—the platform measures 25.4mm x 30.5mm—was one of the biggest challenges. The designers opted to place on one side of the board all of the components that need to go against the body—temperature and optical sensors, for example. Other sensors, such as for ECG, went on the other side of the board. The ECG analog front-end (AFE) was tricky because it requires electrodes—about as big as the board itself—to be attached to said board. To make this work, the designers placed copper pads on the board; the electrodes (both wet and dry) then can attach to these pads. The board ships with wet electrodes and ECG cables. See Figure 1 for a system diagram of the platform.

Figure 1: The hSensor Platform ships with a debugger board, battery holder, USB Type-C and Micro-USB cables, and ECG cables.

The hSensor platform, which was named to EDN’s Hot 100 Products of 2016, brings together various Maxim solutions, providing a faster and easier way for design engineers to evaluate these offerings for a variety of use cases:

  • MAX30205 temperature sensor
  • MAX30101 pulse oximeter and heart-rate sensor
  • MAX14720 power management IC
  • MAX32620 ARMRegistered CortexTm M4F microcontroller
  • MAX30003 biopotential AFE

A three-axis accelerometer, a 6 DOF accelerometer/gyroscope, a barometric pressure sensor, a coin cell battery, a defibrillation protection unit, 32MB flash memory, a USB Type-C connector, and Bluetooth Low Energy module complete the platform. For any developers who want to customize the platform, there is code and firmware available for the ARMRegistered mbedTm IoT Device Platform. Developers can either optimize the firmware for their own specific use case by writing their own code or using the board’s GUI.

Focus on the System, Not Individual Components

Before the Maxim designers began building this platform, they talked to several different companies, from small startups to large enterprises, to better understand customer requirements. One point that stood out was that many companies were focusing so hard on finding the right products and meeting budget requirements that they weren’t looking at the end product as a whole. But for an optimal solution, everything from the sensors to the microcontrollers, power management, and beyond must work well together. “That’s when we thought, why don’t we give customers a way to evaluate a complete solution-level system?” noted Mulpuru. “Ours is not just a sensor-based or an IC-based solution. It’s a system-level solution that enables customers to quickly evaluate their ideas.”