Voltage-controlled oscillator based analog-to-digital converter in 130-nm CMOS for biomedical applications

Abstract

Medical implants and portable wireless sensors are the most serious of biomedical applications due to the dependence on limited battery lifetime. Consequently, energy efficiency integrated circuits designs must be put to higher attention. A particular distinguishing contribution of this paper is its focus on the power consumption that affects battery life and the heat dissipated for biomedical applications. This paper demonstrates a power-efficient implementation of analog-to-digital converter (ADC) based on voltage-controlled oscillator (VCO) to convert the collected analog vital signs into digital data for digital signal processing. The current-starved scheme is employed to implement the VCO efficiently with five-stage which leads to high savings in power and area. D-flip flop (D-FF) scheme is proposed to simplify the hardware architecture of the proposed reset counter. The proposed architecture is implemented with 130 nm CMOS technology and it can perform conversion of analog input signal to digital output using a straightforward hardware structure. The proposed VCO-based ADC achieves improvement in energy saving. Simulation results confirm that this work attains a power dissipation of 0.257 mW and active area of 0.007 mm2, and a very good Walden FOMW of 125 dB. The proposed methodology can implement any number of bits of the ADC by using the appropriate voltage-controlled oscillator with the convenient reset counter.