Heterogeneous Integration of Boost Power Supply and On-Chip Solar Cell using triple well CMOS Process

Abstract

We have been proposed on-chip power supply system for a micro system. This power supply system operates application circuit, to achieve a stand-alone chip, referred to as a micro system. In this work, we fabricate the chip to evaluate the on-chip boost power supply that consists of photovoltaic device, ring oscillator and DC-DC boost converter on the same die. The solar cell using N-well and P-substrate outputs about 500 mV and several μW under about 7600 lx lighting. This solar cell generates negative voltage to the P-substrate but the photoelectric conversion efficiency is much higher than the solar cell generates positive voltage. In this work, the integration method is shown to realize the solar cell with negative voltage output and bootstrap charge pump(BSCP) DC-DC converter using triple well technology. The performance of newly designed BSCP DC-DC converter using MIM capacitor and previously designed BSCP DC-DC converter using MOS capacitor are compared. The converter using MIM capacitor shows the much higher voltage conversion ratio than the converter using MOS capacitor. However, designed on-chip power supply system shows a large variation of the output voltage. We discuss the variation and mismatch with simulation considering parasitic capacitances using corner simulation.