LAUSR

A high-voltage-tolerant and power-efficient stimulator with adaptive power supply is proposed and realized in a 0.18- $\mu \text{m}$ 1.8-V/3.3-V CMOS process. The self-adaption bias technique and stacked MOS configuration are used to prevent issues of electrical overstress and gate-oxide reliability in low-voltage transistors. The on-chip high-voltage generator uses a pulse-skip regulation scheme to generate a variable dc supply voltage for the stimulator by detecting the headroom voltage on the electrode sites. With a dc input voltage of 3.3 V, the on-chip high-voltage generator provides an adjustable dc output voltage from 6.7 to 12.3 V at a step of 0.8 V, which results in a maximal system power efficiency of 56% at a 2400- $\mu \text{A}$ stimulus current. The charge mismatch of the stimulator is down to 1.7% in the whole stimulus current range of 200– $3000~\mu \text{A}$ . The in vivo experiments verified that epileptic seizures could be suppressed by the electrical stimulation provided by the proposed stimulator. In addition, the reliability measurements verified that the proposed stimulator is robust for electrical stimulation in medical applications.