A SC rectification and bin-integration circuit for nerve signal processing: experimental results

In this paper, we describe a low-voltage CMOS switched-capacitor rectification and bin-integration (RBI) circuit dedicated to sensor electronic interfaces. The applications of these interfaces are among others, biomedical and more particularly the implantable devices. RBI is the most common signal processing function applied to the nerve signals. Since the frequency of these signals is below 10 kHz, a switched-capacitor architecture has been used. The circuit comprises an always-valid sample and hold circuit followed by a full wave rectifier. The bin-integration is then performed with three resettable integration stages. The third stage is reset in such a way to use the maximum range of the ADC. The resulting RBI signal is then converted to digital and transferred to the implant central processor where information about bladder could be extracted. The circuit has been realized in CMOS 0.35 μm, 3.3 V technology. The design, simulation and measurement results of the proposed interface are presented. At 1.3 V supply, the measured circuit obtains an RBI error of less than -45 dB for a sinewave input of 7.2 kHz that is the main component of the nerve signal and a dynamic range of ±1.1 V while dissipating 578 μW and occupying a chip area of 5.83 mm².