A 113.6 dB SNR 300μW Switched-Capacitor ΣΔ Modulator with Full-Scale Input Range

A single-loop 3rd-order 1-bit switched-capacitor modulator in 180-nm CMOS technology is presented. A important feature of this modulator is the full-scale input signal range for high-precision and low-power application that is suitable for DC measurement. In order to achieve the full-scale input signal range, an effective signal-scaling circuit is added in the topology. The chopper stabilization technique is incorporated to calibrate the 1/f noise and DC offset. Meanwhile, the zero optimization technique is utilized in the feed-forward topology to optimize the SNR. To further improve the linearity of the modulator, the bootstrapped switches are used in sampling process. The designed modulator achieves 113.6 dB SNR over 250 Hz signal bandwidth with $\pm V_{REF}$ differential input range, while drawing 110$\mu$A current from a 2.7V supply and THD is below -100dB. The chip area is 1.76 mm². This corresponds to FoM of 175.8dB.