An arbitrary waveform stimulus circuit for visual prostheses using a low-area multibias dac

Abstract

Attempts are underway to construct a retinal prosthesis to recover limited vision for blind patients with retinitis pigmentosa using implantable electronic devices. These microchips provide electrical stimulation to damaged retinal tissues using an array of stimulus circuits. This paper describes improvements to conventional circuit designs with significantly decreased implementation area and the ability to support arbitrary stimulus waveforms where an array of such stimulus circuits is required. This yields greater spatial resolution in stimulation owing to more stimulus circuits per chip area. Also introduced are digital-to-analog converter gain prescalar and dc-offset circuits which tune the stimulus circuits to an optimally effective range due to variation in retinal degradation. The prototype chip was fabricated by MOSIS in 1.2-m CMOS technology.Index Terms-Age-related macular degeneration, digitalto-analog converter (DAC), electrical stimulation, retinal prosthesis, retinitis pigmentosa, visual prosthesis.

A Partial-Current-Steering Biphasic Stimulation Driver for Vestibular Prostheses

“…Hence, good fitting is important if the most is to be made of the limited dynamic range of the patient. Consequently, for each stimulation channel, digital settings have been included for programmability [19], [25], [26] of: 1) offset (3-bit); 2) gain (4-bit); and 3) threshold (3-bit). These are intended to: 1) remove any static (operating point) offset caused by process variation and/or device mismatch in preceding hardware; 2) amplify the input stimulus such that the dynamic range is maximized for Fig.…”

A Modular 32-site wireless neural stimulation microsystem

“…Therefore, the stimulator output voltage can change significantly, which should not affect the desired stimulus current level. Cascode or wide swing cascode current mirrors are the conventional current sources that are used in many microstimulator designs including [11]- [16] to generate site-voltage-independent stimulus currents, while providing high output impedance. High output impedance in these cir- [19], [20].…”

“…Full integration and minimization of the number of hybrid components seem to be the only ways to achieve a visual implant with reasonable size. Several researchers have addressed the above problems with limited success [2]- [9], [11]- [16]. This paper presents Interestim-2B (IS-2B), a 32-site wireless microstimulator ASIC with a modular architecture [17].…”

Implantable CMOS neuro-stimulus chip for visual prosthesis

“…A number of implantable visual prostheses for outer retinal degeneration diseases are reported [5][6][7][8][9][10][11][12]. According to their implant locations, these prostheses are named sub-retinal, epi-retinal or optic nerve implants.…”