Design of an implantable stimulator ASIC with self-adapting supply

A high voltage supply is necessary for implantable stimulators that need to deliver high stimulus current to load tissue and overcome large electrode impedance. A constantly high supply voltage results in unnecessary power wastage in low-voltage stimulation and is potentially dangerous at the neural tissue interface. This paper presents the authors´ recent progress in developing a stimulation system with self-adapting supply based on the previous Active Books system. The improved design is able to measure the peak electrode voltage on any specified anode and feed back the information to a central hub unit. If the peak electrode voltage is significantly lower than the current supply voltage, the adjustable voltage regulator in the hub will issue a lower but high enough supply voltage to power up the stimulator chip. The circuit has been designed and simulated in a 0.6-μm HV CMOS process.