A 10-bit CMOS programmable current-source dedicated for a cochlear implant

This paper presents a 10-bit programmable biphasic current-source, which is based on a digital to analog converter (DAC). In order to achieve high accuracy, a current-cell matrix configuration and a switching sequence in a code thermometer have introduced. To minimise the area of the DAC, a two matrix of a same current-cell are used. In this case an only 62 same current-cell are used instead to 1023 for a 10-bit thermometer-code-based DAC architecture. The simulation results have shown that the differential and the integral linearity errors are respectively 0.21 LSB and 0.35 LSB. The biphasic current sources present a good linearity and are capable of generating a maximum current of 1.050 mA through a 1 KΩ load, which is around the typical nerve impedance. This device is designed in a 0.35-μm CMOS technology. The maximum power consumption is 38 mW and the chip size is 175×290 μm².