A New Microstimulator with Pulse Width Modulation
A novel implantable microstimulator has been designed, fabricated, and characterized. The pulse width modulation (PWM) has been used to control the output current source for changing the duration of output waveform. The frequency of output stimulus current can be controlled by a Schmitt trigger based relaxation oscillator. Finally, the intensity of output stimulus current can be programmed by a 5-bit digital code. This circuitry can operate in only 2.5V low voltage to improve the disadvantage of conventional microstimulator that is not suitable in low voltage. In the architecture of circuitry, it reduces the circuit complexity formed by typical microstimulators adopting mircoprocessors as the control unit. The measured results of the proposed microstimulator chip show that this system is quite feasible for different stimulus modes including regular, random and burst modes. This circuitry has been simulated with HSPICE and fabricated in a 0.35μm 2P4M CMOS process.