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

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 1 mA of full scale current at each output from 3.3 V supply, when the output is terminated on 1 KOmega loads.