Toward A Fully Integrated Neurostimulator With Inductive Power Recovery Front-End

Abstract

In order to investigate new neurostimulation strategies for micturition recovery in spinal cord injured patients, custom implantable stimulators are required to carry-on chronic animal experiments. However, higher integration of the neurostimulator becomes increasingly necessary for miniaturization purposes, power consumption reduction, and for increasing the number of stimulation channels. As a first step towards total integration, we present in this paper the design of a highly-integrated neurostimulator that can be assembled on a 21-mm diameter printed circuit board. The prototype is based on three custom integrated circuits fabricated in High-Voltage (HV) CMOS technology, and a low-power small-scale commercially available FPGA. Using a step-down approach where the inductive voltage is left free up to 20 V, the inductive power and data recovery front-end is fully integrated. In particular, the front-end includes a bridge rectifier, a 20-V voltage limiter, an adjustable series regulator (5 to 12 V), a switched-capacitor step-down DC/DC converter (1:3, 1:2, or 2:3 ratio), as well as data recovery. Measurements show that the DC/DC converter achieves more than 86% power efficiency while providing around 3.9-V from a 12-V input at 1-mA load, 1:3 conversion ratio, and 50-kHz switching frequency. With such efficiency, the proposed step-down inductive power recovery topology is more advantageous than its conventional step-up counterpart. Experimental results confirm good overall functionality of the system.

An Integrated Chip High-Voltage Power Receiver for Wireless Biomedical Implants

“…In Figure 12(b), we notice that the substrate leakage current is negligible as the rectifier input node AC does not peak the DC voltage [3]. For high input voltages and load currents, the rectifier is abnormally loaded, and the input AC node voltages become higher than the output DC [3,16]. However, in our application for a neural stimulator, the current required is less than 2 mA, with input voltages ranging from 10-20 V peak , the design proves to be effective.…”

“…In [3], the designed HV rectifier indicated 93% PCE based on the simulation results, but measurement results indicate heavy loading of the rectifier above a 1-mA load current and resulted in latch-up and breakdown of the rectifier. Later, the work in [16] showed the implementation of a half wave rectifier structure to prevent latch-up for higher load current conditions. However, since the rectifier was a half wave structure, the PCE obtained is low.…”

“…In [3,16], IC based on the HV process for receivers in implantable device showed improved power efficiency based on simulation results. An HV IC power recovery system for contact-less memory card [17] reported 50% power efficiency at a higher supply voltage.…”

Implantable RF telemetry for cardiac monitoring in the murine heart: a tutorial review

“…Two principal solutions are currently in widespread use: single-use batteries, such as those used in implantable pulse generators for cardiac pacing, defibrillation, and deep brain stimulation, which are designed to have finite lifetimes and to be replaced surgically at intervals of several years; and inductive power transfer [38], typically accomplished transcutaneously at radio frequencies, as in cochlear implants. Inductive schemes can be used either to supply power continuously or to recharge an implanted power source [36].…”

Prosthetic Power Supplies

“…Combining many technologies and employing smart medical devices within the human body, they allowed a continuous and automatic management of numerous health issues, such as pacemakers and implantable cardiac defibrillators, cochlear implants, bladder controllers, endoscopic capsules, nerve stimulators, lab-on-a-chip, and artificial retinal prosthesis (1)(2)(3)(4)(5). Due to their continuously increasing potential, IMDs are getting more complex, thus requiring more energy to operate (6).…”