Reconfigurable analog-to-digital converter for implantable bioimpedance monitoring

This paper presents a pipelined analog-to-digital converter (ADC) that is designed for implantable bioimpedance monitoring systems. For bioimpedance spectroscopy where the frequency of the excitation current is swept up to high frequencies, the ADC should be adaptable to improve the power efficiency of the system. The converter in this work can configure its resolution and sampling rate based on the input signal amplitude and frequency, respectively. Furthermore, it can automatically decide its configuration with the help of a novel, low-power automatic adaptation circuit. The converter has 10-bit resolution in high-resolution mode and 8-bit resolution in low-resolution mode. The bandwidth of the ADC is 100 kHz in low-speed mode and 20 MHz in high-speed mode. The SNDR, ENOB and power consumption of the converter in low-speed mode are 58.66 dB, 9.45, and 16 μW in 10-bit mode and 46.56 dB, 7.41, and 9 μW in 8-bit mode.