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A. Urso

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9 records found

Bidirectional Bioelectronic Interfaces: System Design and Circuit Implications

System Design and Circuit Implications

Journal article - Yan Liu, A. Urso, R. Martins Da Ponte, T.M. Lopes Marta da Costa, V. Valente, Vasiliki Giagka, Vasiliki Giagka, W.A. Serdijn, Timothy G. Constandinou, Timothy Denison

The total economic cost of neurological disorders exceeds £100 billion per annum in the United Kingdom alone, yet pharmaceutical companies continue to cut investments due to failed clinical studies and risk [1]. These challenges motivate an alternative to solely pharmacological t ...

A Switched-Capacitor DC-DC Converter Powering an LC Oscillator to Achieve 85% System Peak Power Efficiency and -65 dBc Spurious Tones

Journal article - A. Urso, Y. Chen, R.B. Staszewski, Johan F. Dijkhuis, Stefano Stanzione, Y. Liu, W.A. Serdijn, M. Babaie

In this paper, we propose a new scheme to directly power a 4.9-5.6GHz LC oscillator from a recursive switched-capacitor DC-DC converter. A finite-state machine is integrated to automatically adjust the conversion ratio and switching frequency of the converter such that its DC out ...

An Ultra High-Frequency 8-Channel Neurostimulator Circuit with 68% Peak Power Efficiency

Journal article - A. Urso, Vasiliki Giagka, Vasiliki Giagka, M.N. van Dongen, W.A. Serdijn

In order to recruit neurons in excitable tissue, constant current neural stimulators are commonly used. Recently, ultra high-frequency (UHF) stimulation has been proposed and proven to have the same efficacy as constant-current stimulation. UHF stimulation uses a fundamentally different way of activating the tissue: each stimulation phase is made of a burst of current pulses with adjustable amplitude injected into the tissue at a high (e.g., 1 MHz) frequency. This paper presents the design, integrated circuit (IC) implementation, and measurement results of a power efficient multichannel UHF neural stimulator. The core of the neurostimulator is based on our previously proposed architecture of an inductor-based buck-boost dc-dc converter without the external output capacitor. The ultimate goal of this work is to increase the power efficiency of the UHF stimulator for multiple-channel operation, while keeping the number of external components minimal. To this end, a number of novel approaches were employed in the integrated circuit design domain. More specifically, a novel zero-current detection scheme is proposed. It allows to remove the freewheel diode typically used in dc-dc converters to prevent current to flow back from the load to the inductor. Furthermore, a gate-driver circuit is implemented which allows the use of thin gate-oxide transistors as high-voltage switches. By doing so, and exploiting the fundamental working principle of the proposed current-controlled UHF stimulator, the need for a high-voltage supply is eliminated and the stimulator is powered up from a 3.5 V input voltage. Both the current detection technique and the gate driving circuit of the current implementation allow to boost the power efficiency up to 300% when compared to previous UHF stimulator works. A peak power efficiency of 68% is achieved, while 8 independent channels with 16 fully configurable electrodes are used. The circuit is implemented in a 0.18 μm HV process, and the total chip area is 3.65 mm2@en

Analysis and Design of Power Supply Circuits for RF Oscillators

Journal article - A. Urso, Y. Chen, Johan F. Dijkhuis, Yao-Hong Liu, M. Babaie, W.A. Serdijn

This article presents guidelines for designing the power supply blocks of RF oscillators. To preserve their spectral purity, the requirements on the noise and ripple of the supply voltage are firstly evaluated based on the oscillator supply pushing factor and the oscillator Figur ...

Analysis, Design and Implementation of Power-Efficient DC-DC Converters for Biomedical and IoT Applications

Doctoral thesis - A. Urso

This thesis focus on improving the power efficiency of DC-DC converters for two different applications. In the field of implantable medical devices, electrical stimulation has been used as an established treatment for several diseases. It aims to deliver a well-defined amount of charge to the tissue in order to build up a specific electric field and generate or block an action potential. To achieve a large spatial resolution, there is the need for an increasing number of independent stimulating channels to accommodate a large number of stimulating sites. This, however, increases the overall size of the stimulator while potentially affecting the power efficiency. In this respect, the first part of this thesis proposes a multi-channel neural stimulator in which the power efficiency does not depend upon the number of channels being operated simultaneously. On the other hand, in the recently established field of IoT, energy harvesters are increasingly used to ensure a perpetual, but heavily duty-cycled, load operation. However, their typically low output voltage would normally require a boost converter cascaded with a buck converter and low drop-out (LDO) linear regulators to generate multiple supplies of _1V VDD nominal voltage to supply nanoscale CMOS circuits and systems. However, LDOs are noisy, bulky and inefficient. Hence, it seems beneficial for IoT devices to be directly connected to the buck converter. However, the lack of (LDO) isolation exposes supply-sensitive blocks such as LC oscillators to the converter output fluctuations that could severely degrade the system performance. In the second part of this thesis (Chapters 4-6), a noise analysis of a switched-capacitor DC-DC converter reveals that those type of voltage regulators can have an output noise level that is much lower than that of LDOs. They are therefore suitable to power up supply-sensitive blocks. This leads to a new scheme in which an SC DC-DC converter directly powers up an LC oscillator, without consuming additional current or requiring any external component. @en

Activity Dependent Multichannel ADC Architecture using Level Crossing Quantisation for Atrial Electrogram Recording

Conference paper - Aurojyoti Das, S. Rout, A. Urso, W.A. Serdijn

This paper presents a novel multichannel level-crossing (MLC) ADC architecture aimed at recording atrial electrograms from multiple channels. The proposed architecture combines synchronous sampling with level-crossing (LC) quantisation to achieve activity dependent operation whil ...

A Switched Capacitor DC-DC Buck Converter for a Wide Input Voltage Range

Conference paper - A. Urso, W.A. Serdijn

In this paper, a power-efficient multiphase Recursive Switched Capacitor (RSC) converter is presented. Conventionally, RSC converters are used to obtain many different output voltages from a fixed input voltage. Here, the converter provides a fixed output voltage of 1 V at 1 mA ...

An Ultra High-Frequency Multi-Channel Neurostimulator Circuit with Unprecedented Power Efficiency

Abstract - A. Urso, M.N. van Dongen, W.A. Serdijn

None

Comments on 'Compact, energy-efficient high-frequency switched capacitor neural stimulator with active charge balancing (IEEE Transactions on Biomedical Circuits and Systems (2017) 11:4 (878–888) DOI: 10.1109/TBCAS.2017.2694144)

Journal article - A. Urso, Vasiliki Giagka, Vasiliki Giagka, W.A. Serdijn

This manuscript points out some mistakes in the Introduction and in the table of comparison of a paper already published in this journal by Hsu and Schmid [1]. Although the main claim of [1] is still preserved, we believe the paper needs to be rectified for scientific correctness of the work. In [1], the first High Frequency Switched-Capacitor (HFSC) stimulator is presented. The stimulation voltage is derived from the main supply by using an 1 : 1 switched-capacitor DC-DC converter. This particular topology of DC-DC converter operates as a resistor [2]. The further away the output voltage is from the input voltage, the lower the power efficiency is. As a result, the output voltage of the DC-DC converter, and therefore the total charge delivered to the tissue, can only be regulated at the expense of the power efficiency. Section I of [1], provides an overview of the most recently published works in the field of electrical stimulation. Based on the stimulation mode, Hsu and Schmid classify the papers into three categories, named voltage-mode stimulation (VMS), current-mode stimulation (CMS) and switched-capacitor stimulation (SCS). In [1], thework presented in [3] has been classified as SCS.However, [3] proposes CMS which adapts the voltage supply of the neurostimulator to the voltage across the electrodes. In [1], the work presented in [4] has been classified as VMS. However, [4] proposes a CMS. In fact, an inductor-based DC-DC converter without the output capacitance is used to deliver the charge to the tissue. Section V of [1] provides a table of comparison, in which the performances of the stimulator circuit are compared with some relevant contributions found in literature. Several errors have been found in the comparison table. The entries in bold characters and red colour of Table I below corrects the table of comparison presented in [1]. II. CONCLUSION The aim of this comment is two-fold. Firstly, it corrects a classification of the most recent works, which was presented in the Introduction of a paper previously published in this journal [1]. Secondly, it corrects some mistakes in its table of comparison. Although errors have been found, the main claim of [1], and hence its scientific contribution, are still preserved. [Table Presented].@en

Contributed

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ENMOS: Energy Module for Self-Sustainable Wearable Sensors

Master thesis - A.K. Parag, W.A. Serdijn, P.J. French, Q. Fan, A. Urso, A.L. Rodrigues Mansano

This work focuses on addressing the fundamental limitation on the minimum cold start-up voltage that could be harvested from a thermoelectric element (TEG) for human-body wearable applications. For ultra-low DC voltages, the challenge translates to generating a timed-signal to amplify it up to a value that could be used to drive, say, a boost converter which can then start-up the entire energy module. Contemporary works have, thus, strived to accomplish this using a charge-pump-based or a transformer-based approach, which in turn imposes a limit on the minimum TEG voltage that can be harvested. The solution this work proposes is to decouple the Cold Start-up system from the TEG altogether and instead, use a piezoelectric element (PEH). This element being capable of producing a well-timed (AC) signal for free, based on human body vibrations, can potentially drive a boost converter. To this end, an integrated circuit (IC) is designed that can utilize the voltage from the PEH, amplifying it up to generate a well-controlled signal that could operate the boost converter. At the heart of this IC, is a self-reconfigurable charge pump that arranges its stages in different boosting ratios (without any complex logic or DSP) based on the input voltage, to allow for a maximum harvested power. The proposed self-reconfigurable architecture can potentially lead the charge pump to be load-variation-resistant. It achieves this by providing an almost constant voltage while increasing the power for higher load demands, at the same time maintaining a constant efficiency. Thus, the fully on-chip implementation in TSMC 0.18 um CMOS, can cold start-up the system from 25 mV of thermoelectric voltage to deliver an output voltage of 1 V at 56.5 % converter efficiency, consuming only 240.5 pW of dynamic power (simulation). The minimum Cold Start-up voltage and dynamic power were found to be 18 mV (ΔT = 0.1 K) and 231.6 pW respectively, to supply 1 V at 44 % converter efficiency. Moreover, in order to prove that the fundamental limitation on the Cold Start-up voltage has been addressed successfully, the IC was also simulated to check whether it can further be lowered. In this case, by providing a piezoelectric excitation voltage 73.3 mVRMS higher, the Cold Start-up voltage was found to be reduced to 15 mV to supply a constant 1 V at the load. It was also found that increasing the inductor value in this case, can also allow the energy module to support even lower Cold Start-up voltages.