MEDICAL ANALOG DEVICES
Power supply design considerations for primary cell powered remote patient monitors
Fahad Masood, member of technical staff at Analog Devices, says remote patient monitors (RPMs) are continuously evolving to include more features that enable doctors to gain greater insights into their patients’ health.
T
hese features create greater demands on the single-cell batteries that power the monitors. This article provides a power
supply solution for an ECG remote patient monitoring patch that preserves battery life to take advantage of these features. The Internet of Things (IoT) revolution has
allowed for a paradigm shift in the way healthcare providers leverage technology to provide their
patients with real-time care. Today, remote patient monitoring is an area where new medical devices are changing the way doctors interact with their patients. Smaller ICs and wireless communication have
enabled decades old devices to be updated to enhanced functional form factors that increase patient adherence and outcomes. Replacing clunky Holter devices of the past, current remote
patient monitoring patches include a variety of sensors that gather heart rate, temperature, and accelerometer data. These patches transmit patient data to the cloud allowing patients and doctors to access the data in real time. While these devices are increasing the ability
Figure 1: ECG patch power supply diagram. A 235mAh CR2032 lithium coin cell battery provides power to the voltage regulators, microcontroller, ECG front end, temperature sensor, and accelerometer
for doctors to provide better care, they pose challenges for power supply designers who must balance system performance and battery life requirements. The challenges increase further as second-generation patches adopt multimodal turn, increases the demands on the power supply. In this article, we will refer to the ECG RPM patch example shown in Figure 1. This patch continuously monitors the ECG and accelerometer while checking the temperature every 15 minutes. The data are transmitted via Bluetooth Low Energy (BLE) once every two hours for a total of 12 BLE transactions per day. This patch incorporates three different modes temperature monitoring, and transmission modes. In standard monitoring mode, only the ECG and accelerometer are monitored. In temperature monitoring mode, an additional temperature sensor is monitored. In transmission mode, the BLE radio communicates the data while simultaneously monitoring the ECG and accelerometer data
POWER SUPPLY CHALLENGES Designing an RPM, such as an ECG patch, poses multiple challenges for power supply designers. The design is typically space constrained and patches with several sensors may require multiple power rails. Because the RPM patch is usually intended to be a single-use item, a coin cell battery is typically the most cost-effective power source available to the designer. Using only a coin cell battery to supply power to the patch, a of the power supply subsystem. An often overlooked challenge for power supply designers is extending the shelf life of the product. Shutdown currents and battery self-discharge can shorten the life of any system. Therefore, it is important for a designer to determine if the RPM patch can meet operating time requirements after
14 March/April 2025 Irish Manufacturing
www.irish-manufacturing.com
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