A Fully Implantable Opto-Electro Closed-Loop Neural Interface for Motor Neuron Disease Studies

Abstract

This paper presents a fully implantable closed-loop device for use in freely moving rodents to investigate new treatments for motor neuron disease. The 0.18 µm CMOS integrated circuit comprises 4 stimulators, each featuring 16 channels for optical and electrical stimulation using arbitrary current waveforms at frequencies from 1.5 Hz to 50 kHz, and a bandwidth programmable front-end for neural recording. The implant uses a Qi wireless inductive link which can deliver >100 mW power at a maximum distance of 2 cm for a freely moving rodent. A backup rechargeable battery can support 10 mA continuous stimulation currents for 2.5 hours in the absence of an inductive power link. The implant is controlled by a graphic user interface with broad programmable parameters via a Bluetooth low energy bidirectional data telemetry link. The encapsulated implant is 40 mm × 20 mm × 10 mm. Measured results are presented showing the electrical performance of the electronics and the packaging method.

High Efficiency Power Management Unit for Implantable Optical-Electrical Stimulators

“…1.8 V, RV: 3.3 V and HV: 12 V) from an input ac voltage within the ISM frequency band 6.78-13.56 MHz received from the inductive link. As shown in FIGURE 1, the system has four hybrid optical-electrical stimulator units, control logic, and EMG sensor [11] in a single chip for a fully implantable solution. The proposed regulating rectifier features singlestage rectification and regulation with PWM control, an LDO with internal bandgap reference, and a high voltage latch CP with a two-phase non-overlapping clock generator [23].…”

“…The analog PWM controller is shown in FIGURE 6. It consists of an error amplifier (EA) as shown in FIGURE 11 which senses the error between a reference voltage 𝑉 >)H , and 𝑅𝑉 • (𝑅 ! + 𝑅 " )/(𝑅 # + 𝑅 !…”

“…This work is an expansion of [10] and provides further details on the circuit design topology; it includes measured results from the fabricated chip of the PMU highlighted in FIGURE 1. Further circuit details on the stimulator unit and EMG sensor can be found in [11]. The rest of the paper is organized as follows.…”