A Linear Dynamic Voltage Scaling Technique With Adaptive Minimum Voltage Headroom Tracking for Implantable Neurostimulation

This letter presents a linear dynamic voltage scaling (DVS) technique using a dual-loop multistage charge-pump maintaining the minimum voltage headroom for implantable neurostimulation. By adopting an analog DVS with adaptive feedback divider, the stimulus current source could be always kept operating at the boundary of the saturation region and the linear region under different stimulus currents. Furthermore, a simple mode-switched control is introduced to improve the loop response of charge-pump. The design has been fabricated in a 0.18- $\mu $ m BCD process. The DVS technique increases the measured stimulus efficiency up to 52.8% higher than a fixed supply voltage with a peak efficiency of 89.6% in the range of the stimulus current from 0.5 mA to 0.9 mA.