A programmable 9-bit current sources design dedicated to cochlear implant

Abstract

This paper presents a programmable 9-bits current source design for micro-stimulator dedicated to cochlear implant. Such architecture requires a current source permitting to generate bidirectional current multiform. Besides, thanks to a programmable module, flexibility was provided in stimulus generation. In fact, the hearing threshold could be determined, using 3-bits DAC in order to fix the maximum comfortable stimulation, then the stimulation current pulses could be controlled in amplitude, using a 6-bits thermometer DAC, as well as in width. These parameters permit to modulate the charge quantity to be injected later in the cochlea nerve endings. The current sources of the 6-bits DAC have been sized to guaranty low power consumption, a low silicon occupation and an INL of less than 0.4 LSB and a DNL of less than 0.08 LSB. The maximum output providing is about 1mA of full scale current at each output from 3.3V supply, when the output is terminated on 1KΩ loads.I.