Designing Next-Generation Wearable Devices for Remote Patient Monitoring Based on the MAX86178

In the healthcare industry, efforts are being made to find ways to address the influx of patients, manage high costs, and provide better patient outcomes. One theme that is gaining popularity is the move towards a decentralized healthcare system. This represents a clear break from the traditional healthcare system, where patients who need care make an appointment with a doctor and then visit a hospital or clinic. Additionally, one possible way to reduce costs is to detect diseases at their earliest stages, sometimes even before visible symptoms appear. This is an important part of the decentralized healthcare concept and a solution to achieve better and faster results at a lower cost. An immediate benefit is that the patient themselves collects physiological signals regularly, rather than relying solely on doctor visits. It also provides doctors with real-time data that can be reviewed for early disease detection.

Analog Devices is addressing this market with advanced healthcare solutions. This article describes how the next generation of wearable devices can enable a holistic approach to remote patient monitoring, as discussed in a recent press release from the group.

The market for wearable health and wellness devices will grow at a compound annual growth rate (CAGR) of 14% between 2019 and 2025. In 2019, 347 million wearable healthcare products were shipped, and analysts expect this to increase to 754 million by 2025. Although many of these devices are consumer devices, market penetration of wearable medical devices is increasing, as shown in Figure 1. Examples of consumer products are wrist wearables that can detect heartbeat and oxygen saturation (SpO2).

Figure 1: Global wearable market shipments (Mu) during 2018-2025 (Source: Analog Devices)

“Remote patient monitoring (RPM) was gaining interest even before the recent COVID-19 pandemic,” said Andrew Burt, executive business manager for the Industrial and Healthcare business unit at Maxim Integrated, now part of Analog Devices. “In the pandemic era, RPM allows data to be collected without the patient having to visit a hospital or doctor, helping to stop the spread of infectious diseases that we are still battling today.”

Devices such as medical wearable chest patches continuously measure and collect data every minute of every day. These devices then send batches of data to the cloud via smartphones, allowing cardiologists to detect the onset of conditions such as atrial fibrillation (or AFib).

MAX86178

The analog front end (AFE) integrates three measurement systems (optical, ECG, and bioimpedance) in a single chip to obtain four common vital signs: electrocardiogram (ECG or EKG), heart rate (ECG or optical PPG), blood oxygen saturation (SpO2), and respiratory rate (using bioimpedance or BioZ). The company claims that the MAX86178 can achieve synchronized optical PPG and ECG timing to obtain health indicators.

By using this solution, medical device designers reduce annual healthcare costs by replacing traditional office-based health monitoring systems with smaller, lower-power wireless devices that can be worn continuously at home or in the office. The MAX86178 triple-system AFE integrates three clinical-grade subsystems in a single chip. It also replaces discrete implementations by integrating an optical PPG subsystem to measure heart rate and SpO, a single-lead ECG subsystem, and a biopotential and bioimpedance (BioZ) subsystem for measuring respiration rate. Detect vital signs with a small form factor device that packs advanced multiple functions into a 2.6mm x 2.8mm package.

In addition, ADI said that the MAX86178 provides ultra-low power features and configurable options to optimize battery life for specific use cases. This enables the next generation of wearable RPMs to operate at low power, allowing the use of smaller batteries or extending battery life. Figure 2 shows a block diagram of a typical remote monitoring system based on this device.

Figure 2: Block diagram of a remote monitoring system based on the MAX86178 (Source: Analog Devices)

“The device has an excellent signal-to-noise performance of 113dB, which means it can measure SpO2 when worn on the wrist or chest and works with a wide range of skin tones and skin thicknesses, making it suitable for a wide range of situations,” Burt said.

MAX77659

Analog Devices Inc. said its MAX77659 power management IC (PMIC) uses only one inductor to provide multiple output rails (single inductor multiple output or SIMO). The device has an integrated switch-mode buck-boost charger that it claims can charge wearables, hearing aids and IoT devices faster and smaller than any other PMIC on the market.

“When there were switching regulators on the platform, each switching regulator channel required a very bulky inductor and other discrete components,” said Karthi Gopalan, executive director of the Multifunction Power, Battery Power Solutions business unit at Maxim Integrated (now part of Analog Devices). “However, our single-inductor, multiple-output technology can provide three switching outputs with a single inductor. We have been working with this particular family of products for more than four years and have proven that our solution is inherently 50 percent smaller and provides 20 percent longer battery life.”

The MAX77659 SIMO PMIC with a built-in switching charger enables the device to provide (its block diagram is shown in Figure 3) more than 4 hours of gaming time after a brief 10-minute charge. The MAX77659 SIMO PMIC supports autonomous headroom control to reduce heat dissipation by minimizing voltage drop while maintaining headroom to regulate the charging current. Using a single inductor reduces the bill of materials (BOM) by 60% and reduces the total solution size by 50%. In addition to the charger, the MAX77659 SIMO PMIC integrates three independently programmable buck-boost regulators, all of which share a single inductor to minimize the overall solution size. These regulators operate at 91% efficiency under medium to heavy load conditions while consuming only 5μA of quiescent current under light load conditions, extending battery life.

Figure 3: MAX77659 block diagram (Source: Analog Devices)

Gopalan concluded, “Because of the extremely high efficiency of the integrated switching regulators, they operate at 90% efficiency under medium to heavy load conditions, extending battery life, while current consumption is as low as 5 A under light load conditions. We have also implemented autonomous headroom control to reduce heat dissipation by minimizing voltage drop while providing enough headroom to regulate the charge current.”