Low-resistance wide-voltage-range analog switch for implantable neural stimulators

Analog switch is a basic component in neural stimulators as it plays an important role in the control process of opening or closing stimulation, switching electrode polarity or power supply. In implantable stimulator circuit, the switch is usually required to work under a wide-range changing voltage and keep a fairly low on-resistance and low charge injection. In this paper, a switch and its driving system are proposed. The driving system can provide a stable high voltage to drive the NMOS transistor switch, thus solving conflicts between high voltage output and low voltage supply. According to the result from transistor-level simulation based on 0.35um CMOS high-voltage technology, the analog switch can achieve fast speed (ton=70ns, toff=280ns), low and flat resistance (4.5Ohm on average), low charge injection (20pC), extremely low current leak(36pA), and wide working voltage range from 1.8V to 12V, which completely meets the application requirement of neural stimulators.