27.3 A Sub-1V 14b 5.8nW/Hz BW/Power-Scalable CT Sensor Interface with a Frequency-Controlled Current Source Achieving a 225× Scalable Range

Precision and energy-efficient sensor interfaces have always been needed in loT applications. To digitize weak signals (tens of mVs), such as shunt-based current and biomedical sensors, the interface should have low noise [1]–[4]. Moreover, to accommodate different use cases, the bandwidth (BW) and power dissipation of sensor interfaces should be highly scalable [5]–[7]. Sensor interfaces based on discrete-time (DT) ADCs, such as SAR ADCs [8], [9] and FIA-based ΔΣ ADCs [5]–[7] are BW/power scalable, but they usually suffer from kT/C noise (Fig. 27.3.1 top, left). Using a continuous-time (CT) first stage, such as an instrumentation amplifier (IA) [1], [3], [4] (Fig. 27.3.1 top, right), or an active RC integrator [10], [11], can suppress the sampling noise of the following stages, however, they usually consume fixed static power, limiting their BW/power scalability.