Abstract
Power supply quality and stability are critical for wearable and implantable biomedical applications. For this reason we have designed a reconfigurable switched-capacitor DC-DC converter that, aside from having an extremely small footprint (with an active on-chip area of only 0.04 mm), uses a novel output voltage control method based upon a combination of adaptive gain and discrete frequency scaling control schemes. This novel DC-DC converter achieves a measured output voltage range of 1.0 to 2.2 V with power delivery up to 7.5 mW with 75% efficiency. In this paper, we present the use of this converter as a power supply for a concept design of a wearable (15 mm × 15 mm) 1-lead ECG front-end sensor device that simultaneously harvests power and communicates with external receivers when exposed to a suitable RF field. Due to voltage range limitations of the fabrication process of the current prototype chip, we focus our analysis solely on the power supply of the ECG front-end whose design is also detailed in this paper. Measurement results show not just that the power supplied is regulated, clean and does not infringe upon the ECG bandwidth, but that there is negligible difference between signals acquired using standard linear power-supplies and when the power is regulated by our power management chip.
Highlights
As the global population of persons over 60 years of age continues to increase, health-care solutions that reduce the burden on an already stressed health-care and welfare system are required
The relatively wide availability of microelectronics with embedded software, open access wireless protocols and longer battery life has led to the research and development of wearable, wireless bio-sensor systems that can be worn on the body and integrated into clothing
We have proposed a feasible system architecture of a wearable ECG-front device that uses an energy-harvester and a power converter to supply regulated power to an ECG front-end circuit that can measure ECG signals and a microcontroller that can be used to process and transmit the ECG
Summary
As the global population of persons over 60 years of age continues to increase, health-care solutions that reduce the burden on an already stressed health-care and welfare system are required. It is important for such devices to have a stable and effective power supply accompanied by a good power management system in order to maximize battery life and avoiding the need for replacement batteries or frequent recharging. These devices must be small and light-weight to fit in the paradigm of wearable/implantable devices. Switched-capacitor (SC) DC-DC power converters are a suitable choice for these devices [5,6] They require less die area overhead and are low-cost and more compact than standard switched-mode power supplies. Test measurements have been taken to verify the operation of the ECG front-end with the power management chip and results show that it works extremely well in this application, making it possible to measure ECG signals that are accurate and free of additive distortion
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