An ECG Patch Combining a Customized Ultra-Low-Power ECG SoC with Bluetooth Low Energy for Long Term Ambulatory Monitoring Marco Altini, Salvatore Polito, Julien Penders Holst Centre / imec the Netherlands High Tech Campus 31. Eindhoven, The Netherlands marco.altini@imec-nl.nl, salvatore.polito@imec-nl.nl, julien.penders@imec-nl.nl Hyejung Kim, Nick Van Helleputte, Sunyoung Kim, Firat Yazicioglu imec imec, B-3001. Leuven, Belgium hyejung.kim@imec.be, nick.vanhelleputte@imec.be, sunyoung.kim@imec.be, refet.firat.yazicioglu@imec.be ABSTRACT This paper presents the development of an ECG patch aiming at long term patient monitoring. The use of the recently standardized Bluetooth Low Energy (BLE) technology, together with a customized ultra-low-power ECG System on Chip (ECG SoC), including Digital Signal Processing (DSP) capabilities, enables the design of ultra low power systems able to continuously monitor patients, performing on board signal processing such as filtering, data compression, beat detection and motion artifact removal along with all the advantages provided by a standard radio technology such as Bluetooth. Early tests show how combining the ECG SoC and BLE leads to a total current consumption of only 500µA at 3.7V, while computing beat detection and transmitting heart rate remotely via BLE. This allows up to one month lifetime with a 400mAh Li-Po battery. Categories and Subject Descriptors J.3 [Computer Applications]: Life & medical sciences – Health. General Terms Performance, Design, Experimentation. Keywords ECG patch, Bluetooth Low Energy, mHealth. 1. INTRODUCTION It is foreseen that healthcare system and services will radically change in the near future. Small and low power sensors able to monitor vital signs and activity patterns can provide a great opportunity in shifting to a new patient centric paradigm, characterized by the delocalization of care from hospitals to home, and a focus on prevention and just-in-time intervention. Cardiac disease is the leading cause of death in the U.S. and it is well established that early detection is critical for survival. Wearable sensors play a key role in continuous chronic disease monitoring during a person’s daily life, allowing for both just-in-time interventions and more accurate diagnosis. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Wireless Health ‘11, October 10-13, 2011, San Diego, USA. Copyright 2011 ACM 978-1-4503-0982-0...$10.00. The emphasis on individual health and well-being recently increased, triggering the development of many products and research prototypes targeting this field [1-5]. The first group often employs ultra-low power radios and protocols in order to save power, together with general purpose microcontrollers, lacking wearability, standardization, ease of use, and ultra low power processors for on board signal processing (DSPs) [1-3]. In the latter group, some systems offer reliable, easy to use sensors, equipped with Bluetooth (BT) radios that allow plug and play functionalities with mobile phones and PCs. [4] and [5] are two examples of such systems. The trade-off this time is on power consumption, since these systems can last for only a few hours, in fact limiting significantly practical application and usefulness of the devices for long term monitoring. In this paper, we report an ECG patch based on the combination of an ultra-low power ECG SoC, and Bluetooth Low Energy, overcoming the lack of wearability, standardization or lifetime of previous systems. 2. SYSTEM DESCRIPTION 2.1 System Architecture Figure 1. Hardware architecture of the ECG Patch. The ECG patch can be functionally divided into two subsystems. The first one is the mixed signal ECG SoC [6], which in turn consists of three main parts: an Analog Front-End (AFE), a 12 bit Analog to Digital Converter (ADC) and a custom Digital Signal Processing (DSP) back-end. The AFE supports concurrent 3- channel ECG monitoring, with impedance measurements and band-power extraction. The 12-bit ADC with adaptive sampling scheme, capable of compressing the ECG data by a factor of 5, reduces the power consumption due to data processing and transmission. The DSP back-end, using SIMD processor architecture, hardwired accelerate unit, effective duty cycling, instruction cache, and clock gating scheme, provides low power