A 0.6V 2.9µW mixed-signal front-end for ECG monitoring

Abstract

This paper presents a mixed-signal ECG front-end that uses aggressive voltage scaling to maximize power-efficiency and facilitate integration with low-voltage DSPs. 50/60Hz interference is canceled using mixed-signal feedback, enabling ultralow-voltage operation by reducing dynamic range requirements. Analog circuits are optimized for ultra-low-voltage, and a SAR ADC with a dual-DAC architecture eliminates the need for a power-hungry ADC buffer. Oversampling and ∆Σ-modulation leveraging near-VT digital processing are used to achieve ultralow-power operation without sacrificing noise performance and dynamic range. The fully-integrated front-end is implemented in a 0.18µm CMOS process and consumes 2.9µW from 0.6V.

A Scalable, 2.9 mW, 1 Mb/s e-Textiles Body Area Network Transceiver With Remotely-Powered Nodes and Bi-Directional Data Communication

“…The received power peaks at 20 µA load current and the peak dc-to-dc power transfer efficiency across the link is 1.2% with voltage transfer function of 0.29, which are smaller by approximately 25% than the values calculated in Section III since Equations (1) and (2) ignore the effects of the source resistance R s in Figure 6. Of a maximum 34 µW power recovered at the sensor node, a maximum of 14 µW is consumed by the communication and digital baseband circuits, leaving the remaining 20 µW for the biomedical signal acquisition front-end which is sufficient to power state-of-the-art biomedical data-acquisition circuits [2]- [4]. A plot of the measured efficiency and output power normalized to its maximum value with varying misalignment is presented in Figure 22.…”

“…The on-chip NNI module supplies power to the sensor readout circuitry and transmits the data measured by it. The off-chip readout circuits consist primarily of a front-end amplifier followed by an ADC and can be any state-of-the-art microwatt-level sensor that measures signals on the human body [2]- [4]. An auto-commutative rectifier (ACR) minimizes the dead zone for rectification at low-amplitude ac inputs, and converts ac power transmitted by the base station to dc for use by all circuits at the sensor node.…”

“…The loop transfer function for the oscillator has three poles and no zeros, making the system oscillate above a minimum dc loop gain. This dc loop gain is provided by 2 The value of Rs for the highest and lowest power settings of the transmitter are approximately 140 Ω and 480 Ω respectively. the small-signal amplification of the class-D PA, which is dcbiased around mid-rail by negative feedback.…”

“…Current state-of-the-art biomedical front-ends [2]- [4] can measure signals using only microwatts of power, making it possible to aggressively minimize their volume and the amount of energy stored locally. In order to realize their potential afforded by these advantageous traits, it makes sense to transfer the data using a two step process.…”

Design of Low-Voltage Digital Building Blocks and ADCs for Energy-Efficient Systems

“…The work in [5] and [6] are demonstrations of mixedsignal implementations targeted for low-voltage operation to improve energy efficiency. To achieve maximum energy savings, voltage scaling should be supported by algorithms, architectures and circuits optimized for the specific requirements of the target application [7].…”