A 14-b Energy-Efficient BW/Power Scalable CTDSM With a Frequency-Controlled Current Source

This work presents a 14-bit energy-efficient bandwidth (BW)/power scalable continuous-time delta–sigma modulator (CTDSM) for sensor interfaces in IoT applications. To ensure low noise for small input signals and achieve BW/power scalability, it is built around Gm-C integrators biased via a linear frequency-controlled current source (FCCS). The FCCS enables the integrators to maintain a nearly constant output swing and linearly scalable power consumption across a wide sampling frequency ( $f_{s}$ ) range. Furthermore, multi-bit quantization and dead-band (DB) switches are applied to suppress the nonlinearity of the open-loop Gm-C integrator and DAC transient glitches, respectively. Fabricated in a standard 130-nm CMOS process, it occupies an active area of 0.29 mm². With an input of ±80 mV, the proposed CTDSM demonstrates a nearly constant peak SNDR (~85 dB) and a stable energy efficiency over a $225\times $ scaling range of $f_{s}$ under a 0.9-V supply. When operating at a typical sampling frequency of 1 MHz, it achieves an input-referred noise density of 46 nV/ $\surd $ Hz, and a state-of-the-art energy efficiency.