A Fully Integrated Stimulator With High Stimulation Voltage Compliance Using Dynamic Bulk Biasing Technique in a Bulk CMOS Technology

This paper presents a fully integrated stimulatorusing a dynamic bulk biasing technique and a dynamic controlscheme in a 180-nm bulk CMOS technology. Unlike the conven-tional bulk biasing method, the bulk bias voltage is dynamicallyset according to the different stimulation phases. It avoids theunderlying leakage current paths, and improves the maximumstimulation voltage compliance (MSVC). Together with dynamicbulk biasing scheme, a high voltage interface is designed toovercome the limitation of the breakdown voltage of the substratediode (VBD) between the high and low voltage domains. An all-NMOS dynamic charge pump is also proposed as a dynamicpower supply aboveVBDand provides dynamic bulk-biasingvoltages. Fabricated in a 180-nm standard CMOS technology,the stimulator achieves an MSVC of +/- 16.5 V under a 3.3-Vsupply, and the achieved MSVC is similar to 1.11 times higher than theVBD(similar to 14.8 V) of the substrate diode. The stimulator is alsomeasured in a continuous output test mode for over 10 millioncycles, the variation of|MSVC|is less than 200 mV.