A Chip for an Implantable Neural Stimulator
01 Jan 2000-Vol. 22, Iss: 1, pp 81-89
TL;DR: In this paper, the authors describe a chip for a multichannel neural stimulator for functional electrical stimulation (FES), which is able to generate charge-balanced current pulses with a controllable length up to 256 μs and an amplitude up to 2 mA.
Abstract: This paper describes a chip for a multichannel neural stimulator for functional electrical stimulation (FES). The purpose of FES is to restore muscular control in disabled patients. The chip performs all the signal processing required in an implanted neural stimulator. The power and digital data transmission to the stimulator passes through a 5 MHz inductive link. From the signals transmitted to the stimulator, the chip is able to generate charge-balanced current pulses with a controllable length up to 256 μs and an amplitude up to 2 mA, for stimulation of nerve fibers. The quiescent current consumption of the chip is approx. 650 μA at supply voltages of 6–12 V, and its size is 3.9×3.5 mm^2. It has 4 output channels for use in a multipolar cuff electrode.
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TL;DR: In this paper, the design and implementation of fully integrated rectifiers in BiCMOS and standard CMOS technologies for rectifying an externally generated RF carrier signal in inductively powered wireless devices, such as biomedical implants, radio-frequency identification (RFID) tags, and smartcards to generate an on-chip dc supply.
Abstract: This paper describes the design and implementation of fully integrated rectifiers in BiCMOS and standard CMOS technologies for rectifying an externally generated RF carrier signal in inductively powered wireless devices, such as biomedical implants, radio-frequency identification (RFID) tags, and smartcards to generate an on-chip dc supply. Various full-wave rectifier topologies and low-power circuit design techniques are employed to decrease substrate leakage current and parasitic components, reduce the possibility of latch-up, and improve power transmission efficiency and high-frequency performance of the rectifier block. These circuits are used in wireless neural stimulating microsystems, fabricated in two processes: the University of Michigan's 3-/spl mu/m 1M/2P N-epi BiCMOS, and the AMI 1.5-/spl mu/m 2M/2P N-well standard CMOS. The rectifier areas are 0.12-0.48 mm/sup 2/ in the above processes and they are capable of delivering >25mW from a receiver coil to the implant circuitry. The performance of these integrated rectifiers has been tested and compared, using carrier signals in 0.1-10-MHz range.
292 citations
Cites background from "A Chip for an Implantable Neural St..."
...implant designs, the rectifier block is either a hybrid diode bridge [4], [5], which increases the size of the implant, or an...
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TL;DR: This invited paper covers several techniques and methods employed to build high reliability circuits and systems dedicated to implement advanced implantable and wirelessly controlled smart medical devices such as sensors and microstimulateurs.
Abstract: Innovative circuits and systems techniques are required to build advanced smart medical devices (SMD). The high reliability and very low power consumption are among the main criteria that must be given priority to implement in such implantable and wirelessly controlled microsystems. A typical device is composed of several integrated modules to be assembled on a thin substrate providing placement flexibility in the body. Monitoring of electrode-tissue interface condition is needed for enhanced safety, and for enabling troubleshooting after implantation. In order to improve controllability and observability, fully integrated binary phase-shift-keying (BPSK) demodulation combined with a passive modulation method allows full-duplex data high data rate communication between external controllers and implants. Case studies such as peripheral nerve interfaces to recuperate bladder functions, cortical multichannel stimulator, as well as cortical monitoring devices are reported.
202 citations
TL;DR: A fully integrated binary phase-shift keying (BPSK) demodulator, which is based on a hard-limited COSTAS loop topology, dedicated to such implantable medical devices, which may improve the controllability and observability of the overall implanted system.
Abstract: During the past decades, research has progressed on the biomedical implantable electronic devices that require power and data communication through wireless inductive links. In this paper, we present a fully integrated binary phase-shift keying (BPSK) demodulator, which is based on a hard-limited COSTAS loop topology, dedicated to such implantable medical devices. The experimental results of the proposed demodulator show a data transmission rate of 1.12 Mbps, less than 0.7 mW consumption under a supply voltage of 1.8 V, and silicon area of 0.2 mm/sup 2/ in the Taiwan Semiconductor Manufacturing Company (TSMC) CMOS 0.18-/spl mu/m technology. The transmitter satisfies the requirement of applications relative to high forward-transferring data rate, such as cortical stimulation. Moreover, the employment of BPSK demodulation along with a passive modulation method allows full-duplex data communication between an external controller and the implantable device, which may improve the controllability and observability of the overall implanted system.
182 citations
Cites background from "A Chip for an Implantable Neural St..."
...[4] described a chip for a multichannel neural stimulator for FES....
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TL;DR: In this paper, a review of the most popular techniques to harvest energy for implantable biosensors is presented, focusing on the inductive links that are able to deliver power wirelessly through the biological tissues and enable bidirectional data communication with the implanted sensors.
Abstract: This paper reviews some popular techniques to harvest energy for implantable biosensors. For each technique, the advantages and drawbacks are discussed. Emphasis is placed on the inductive links that are able to deliver power wirelessly through the biological tissues and enable bidirectional data communication with the implanted sensors. Finally, high-frequency inductive links are described, focusing also on the power absorbed by the tissues.
170 citations
TL;DR: This paper presents a new active approach for charge balancing using long-term offset regulation, which is compared to a previously introduced active charge balancer as well as commonly used passive balancing techniques.
Abstract: Charge balancing is a major concern in functional electrical stimulation, since any excess charge accumulation over time leads to electrolysis with electrode dissolution and tissue destruction. This paper presents a new active approach for charge balancing using long-term offset regulation. Therefore, the electrode voltage is briefly monitored after each stimulation cycle and checked if it remains within a predefined voltage range. If not, an offset current is adjusted in order to track the biphasic current mismatch in upcoming stimulations. This technique is compared to a previously introduced active charge balancer as well as commonly used passive balancing techniques. Subsequently, the techniques are verified through experiments on a platinum black electrode in 0.9% saline solution.
155 citations
Cites background from "A Chip for an Implantable Neural St..."
...By calculating or measuring the charge in the stimulation phase, the amplitude and length of the relevant discharge phase were derived [16]–[18]....
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References
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TL;DR: Results indicated that the use of transverse field steering current improved selectivity in cats to study selective activation of medial gastrocnemius, soleus, tibialis anterior, and extensor digitorium longus with a cuff electrode.
Abstract: Acute experiments were performed on adult cats to study selective activation of medial gastrocnemius, soleus, tibialis anterior, and extensor digitorium longus with a cuff electrode. A spiral nerve cuff containing twelve dot electrodes was implanted around the sciatic nerve, and evoked muscle twitch forces were recorded in six experiments. Spatially isolated dot electrodes in four geometries (monopolar, longitudinal tripolar, tripolar with four common anodes, and two parallel tripoles) were combined with transverse field steering current(s) from an anode(s) located 180 degrees around from the cathode(s) to activate different regions of the nerve trunk. A selectivity index was used to construct recruitment curves for a muscle with the optimal degree of selectivity. Physiological responses were correlated with the anatomical structure of the sciatic nerve by identifying the nerve fascicles innervating the four muscles, and by determining the relative positions of the electrodes and the nerve fascicles. The results indicated that the use of transverse field steering current improved selectivity. The relative performance of the various electrode arrangements is discussed. >
420 citations
"A Chip for an Implantable Neural St..." refers background in this paper
...Cuff electrodes are suitable for selective stimulation of relatively large nerves [9, 10 ], such as the peroneal nerve in the lower leg....
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TL;DR: The experimental results show that the charge injection limits of a Pt electrode using 0.2 ms charge balanced, biphasic current pulses range from 50 to 150 mu C/cm/sup 2/ geometric if the potential excursions of the electrode are kept below those at which H/ sub 2/ or O/sub 2/ are produced.
Abstract: For pt.VII see J. Neurosci. Methods, vol.9, p.301-8 (1983). The charge injection limits of a Pt electrode using 0.2 ms charge balanced, biphasic current pulses range from 50 to 150 mu C/cm/sup 2/ geometric if the potential excursions of the electrode are kept below those at which H/sub 2/ or O/sub 2/ are produced. These charge densities are three to ten times smaller than the currently accepted value based on earlier experiments in which the reversible surface reactions were fully utilized and the pulse widths were longer. Several qualifying comments are made regarding the experimental results. >
370 citations
TL;DR: Describes the design, fabrication, and output capabilities of a microminiature electrical stimulator that can be injected in or near nerves and muscles and used successfully for chronic stimulation in hindlimb muscles of cats.
Abstract: Describes the design, fabrication, and output capabilities of a microminiature electrical stimulator that can be injected in or near nerves and muscles. Each single channel microstimulator consists of a cylindrical glass capsule with hermetically sealed electrodes in either end (2-mm diameter/spl times/13-mm overall length). Power and digital control data can be transmitted to multiple implants (256 unique addresses) via a 2-MHz RF field created by an external AM oscillator and inductive coil. In vitro testing demonstrated accurate control of output pulsewidth (3-258 /spl mu/s in 1-/spl mu/s steps) and current (0-30 mA in two linear ranges of 16 steps each, up to 8.5 V available compliance voltage). Microstimulators were used successfully for chronic stimulation in hindlimb muscles of cats. Design and fabrication issues affecting yield and reliability of the packaging and electronics are discussed.
294 citations
TL;DR: The first implant configuration realized from this modular system is targeted for clinical implementation in persons with tetraplegia at the C6 level for restoration of hand function, using wrist position as the command control source.
Abstract: An implantable integrated stimulator and telemetry system has been developed. The system is capable of fulfilling the stimulus and telemetry needs of advanced functional neuromuscular stimulation (FNS) applications requiring multiple channels of stimulation and multiple channels of sensor or biopotential sensing. This system provides a command control structure, an inductive radio frequency link providing power to the implant device as well as two-way transcutaneous communication, an ASIC for decoding the command and for providing functional control within the implant, and modular circuitry providing the application specific implant functions. Biocompatible hermetic packaging, lead systems, and in-line connectors suitable for long-term implantation, provide encapsulation for the circuitry and access to the electrodes and sensors used in the application. The first implant configuration realized from this modular system is targeted for clinical implementation in persons with tetraplegia at the C6 level for restoration of hand function, using wrist position as the command control source. The implant device realized has ten channels of stimulation and telemetry used to control and sense a joint angle transducer implanted in the radio-carpal joint of the wrist. A prototype device has been fabricated and is undergoing testing in an animal.
284 citations
"A Chip for an Implantable Neural St..." refers background in this paper
...On the other hand, stimulators have been presented with one central processing unit, and wire connections out to the stimulation sites [ 5 ]....
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TL;DR: The most effective design was one in which a thin sheath of silicone rubber was wrapped around and intra-operatively sealed to a longitudinally slit, tripolar cuff made by dip-coating silicone over stranded stainless steel leads that were prepositioned on a mandrel using polyvinyl alcohol as a temporary adhesive.
247 citations
"A Chip for an Implantable Neural St..." refers background in this paper
...Cuff electrodes are suitable for selective stimulation of relatively large nerves [ 9 ,10], such as the peroneal nerve in the lower leg....
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