An 8MHz 31.25kS/s Impedance-Monitoring IC Based on IF-Sampling Architecture with a Band-Pass Delta-Sigma ADC

Abstract

We present an impedance-monitoring IC achieving a wide frequency range (FR) and fast output data rate (ODR). The proposed IC support a wide FR with improved spectral density by down-converting the signal to the intermediate frequency (fIF) in front of the instrumentation amplifier (IA) using the LO signal generated by a single-side-band (SSB) mixer. The proposed IF-sampling architecture does not require narrow-bandwidth (BW) low-pass filter (LPF), resulting in a fast ODR. A time-interleaved (TI) DFT is also employed to further improve the ODR. A band-pass delta-sigma ADC (BP-ΔΣ-ADC) with the auto-calibration and BP truncation is adopted to achieve the best noise performance at fIF. The fabricated IC achieves 0.35ΩRMS resolution in the FR from 4kHz to 8MHz with 122.1Hz BW while providing the ODR up to 31.25kS/s.