Design of Multiple-Charge-Pump System for Implantable Biomedical Applications

Abstract

Circuit design to implement a multiple-charge-pump (MCP) system in a low-voltage standard CMOS process is proposed, that can successfully support the desired power sources for implantable monopolar biphasic stimulator. A negative charge pump (CP) circuit with the four-phase cross-couple structure is introduced to suppress return-back leakage, and thus its power efficiency is improved. This MCP system provides the stimulator with three power sources of +9V, -9V, and -2.7V, simultaneously. Closed-loop operation helps for regulating the output voltage sources (+9V and -9V) with a maximum loading current of 5.5mA for stimulus drivers, and 1-mA current for the control circuits of the stimulator. The proposed MCP system has been fabricated in a 0.18-mu m 1.8V/3.3-V CMOS process, as well as successfully verified in in-vivo animal tests with stimulator together.