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

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

Urso, A. (TU Delft Bio-Electronics)
Giagka, Vasiliki (TU Delft Bio-Electronics; Fraunhofer Institute for Reliability and Microintegration IZM)
van Dongen, M.N. (NXP Semiconductors)
Serdijn, W.A. (TU Delft Bio-Electronics)

2019

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

Buck-boost DC-DC converter
high power efficiency
low power
multichannel
neural stimulation
ultra high frequency stimulation

http://resolver.tudelft.nl/uuid:2cab51b4-5005-4f86-9a5b-024529d19177

https://doi.org/10.1109/TBCAS.2019.2920294

1932-4545

IEEE Transactions on Biomedical Circuits and Systems, 13 (5), 882-892

Accepted author manuscript

Institutional Repository

journal article

© 2019 A. Urso, Vasiliki Giagka, M.N. van Dongen, W.A. Serdijn