A 8.9 $\beta$ W 12.3-ENOB SAR ADC with <1 LSB DNL/INL for Electrochemical Impedance Spectroscopy in 12nm CMOS

Le résumé fourni par la source

In this work we present an ultra-low-power differential successive approximation register (SAR) analog-to-digital converter (ADC) for electrochemical impedance spectroscopy application. The target is measurement of complex bioimpedance of cells proliferating on a membrane inside a microfluidic channel for organ-on-chip applications. For this, a differential AC current excitation in the low frequency range is injected via a pair of electrodes, while a differential voltage is sensed for readout via another pair of electrodes. From the evaluated complex impedance of the cell layer the transepithelial electrical resistance (TEER) can be obtained. It can vary from few Ohms to several kilo-Ohms, posing challenging requirements on the Signal-to-Noise-Ratio (SNR) of the ADC in the voltage processing chain. On the other hand, differential signalling enables use of efficient techniques for differential SAR ADCs. The presented SAR ADC is implemented in a 12nm CMOS technology and dissipates$8.9 \mu ~\mathrm{W}$including analog, digital and reference voltage supply. The prototype SAR ADC achieves a signal-to-noise ratio (SNR) of 76 dB and an SFDR of 54.2 dB at a sampling rate of$256 \text{kS} / \mathrm{s}$. The circuit occupies a core chip area of only$545 \times 235 \mu \mathrm{m}^{2}$.

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