신경 보철 장치를 위한 체내 이식용 회로 설계

Abstract

This paper describes a design and implementation of an implantable circuit for neural prosthetic devices. It is recommended that the circuit should provide charge-balanced biphasic current pulses and the function of monitoring impedance of the electrode for safe and effective current stimulation. In our design, the current pulses are provided from binary weighted 8 current sources through switch network. And to implement the recording function we designed the voltage-to-time converter which converts the voltage measured between two electrodes into pulse duration of the output signal. The signal is sent to out-of-body by load modulation through bidirectional coil communication. And we proposed the pulse counting circuit in order to improve the robustness of being immune to the skin depth between two coils. The designed circuit was fabricated in 0.8 ㎛ High Voltage CMOS process. The pulse counting circuit successfully decodes the received signal from the implanted coil in the skin depth of up to 13mm at the data transmission rate of 125kbps with bit error rate of better than 1X10-6. The current can range from 0 to 1.86mA in 7.3uA steps. The chip was capable of providing 8000 pulses/s and sampling electrode voltage from 0.5V to 4.5V.