A 4.5 mW CT Self-Coupled <formula formulatype="inline"><tex Notation="TeX">$\Delta\Sigma$</tex></formula> Modulator With 2.2 MHz BW and 90.4 dB SNDR Using Residual ELD Compensation

Abstract

This paper presents a power-efficient single-loop continuous-time (CT) $\Delta\Sigma$ modulator (DSM) that achieves a SNDR of 90.4 dB over a 2.2 MHz signal bandwidth. The modulator uses a fourth-order feed-forward architecture incorporating the continuous-time self-coupling (CTSC) technique. Moreover, to reduce hardware area, this design utilizes the residual signal for excess loop delay (ELD) compensation. To improve linearity, low-ripple DAC latches and low toggle-rate dynamic element matching (DEM) algorithm are adopted. This DSM is fabricated in a 55 nm LP CMOS technology. Operating at 140 MHz sampling rate, the chip consumes 4.5 mW from power supplies of 1.2 V and 1.8 V. It achieves 90.4 dB SNDR and 92 dB dynamic range (DR) with a 2.2 MHz signal bandwidth, resulting in a Schreier FOM of 177.3 dB and 178.9 dB based on SNDR and DR, respectively. The chip area is 0.09 mm $^{2}$ .