Programmable current source dedicated to implantable microstimulators

In this paper, a survey of programmable current-source architectures based on miniaturized digital-to-analog converters (DAC) is elaborated to propose a new design dedicated to a visual microstimulator. The needed current-source constitutes the electronic interface to tissues. A few samples of this current-source will be integrated in an implantable device which is powered and controlled using an electromagnetic coupling technique. The main objective is to select a design that meets as close as possible criteria related to the implant such as reliability, flexibility, energy efficiency and integration area. Consequently, an adequate current source is proposed which is a 5-bit thermometer-code-based DAC architecture. The resulting circuit is simulated using a 0.35 μm CMOS technology from PMC-Sierra available through the Canadian Microelectronics Corporation (CMC)