A subthreshold low-power CMOS LC-VCO with high immunity to PVT variations

This paper presents a current driver with a novel high voltage (HV) switch schematic for the use as a protective switch for recording circuits during the stimulation sequence in neural measurement system. The current driver can source and sink currents of amplitudes up to ±8.2 mA with a HV tolerance from 30 V up to 120 V. The proposed HV switch also tolerates the voltage difference up to 120 V between its terminals. Between stimulation sequences the driver provides the effective isolation of the stimulation electrode from ground and HV supply voltage. The inter pulse current is no more than 60 pA. The chip was fabricated with AMS HV 0.35 (mu)m CMOS technology. For test purposes the complete stimulation system including the proposed chip and the external C8051F410 controller was build. For the proposed system the mismatch between the sourced and sinked current does not exceed 20 (mu)A. The possibility to stimulate with frequencies up to 1 kHz is proven by measurement along with the electrode-tissue model.