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A 160MHz-BW 68dB-SNDR 30.8mW Continuous-Time Pipeline DSM with Correlative Passive Low-Pass Filters and DAC Image Pre-Filtering
Li, Ke1; Congzhou, Xianyu1; Qi, Liang2; Guo, Mingqiang1; Martins, Rui P.1,3; Sin, Sai Weng1
2024
Conference NameIEEE Custom Integrated Circuits Conference (CICC)
Source PublicationProceedings of the Custom Integrated Circuits Conference
Conference Date21-24 April 2024
Conference PlaceDenver, CO, USA
PublisherInstitute of Electrical and Electronics Engineers Inc.
Abstract

Latest wireless communication systems desire ADCs to pursue wide-BW (160MHz) and high-DR (65dB) to support ever-increasing data transfer rates and higher-order modulation schemes. Continuous-time (CT) pipeline ADC/DSM draws growing attention as it combines the easy-to-drive and inherent anti-aliasing merits of CT operation with adequate resolution from pipeline operation, where OSR is restricted by high sampling frequency (Fs). Meanwhile, when GHz-Fs is utilized to broaden the signal BW in the CT pipeline converter, two design issues arise related to the front-end stage: 1) path delay mismatch between input signal path and quantization (QTZ) path; 2) image signal produced by switching of DAC on QTZ path, which lies on integer multiples of Fs and easily saturates the backend stage. This paper proposes a CT pipeline DSM with correlative passive RC low-pass filters (LPFs) that help alleviate the abovementioned issues. The DAC image filtering in residue amplifier (RA) is moved to the QTZ path and realized by a simple RC-LPF2, which pre-filters the DAC image before the DAC current is injected into the RA, reducing the RA's swing, slew rate, and its associated power consumption. On the other hand, another RC-LPF1 is inserted into the analog signal path to emulate the required delay that matches the operation time of the QTZ path. Benefits from the RC components correlation between RC-LPF1 and RC-LPF2, this structure avoids the usage of the LC- or tuned-RC-lattice all-pass/low-pass filter (APF/LPF) in the front-end stage [1]-[3]. For the back-end design, an APF analog delay is proposed to be inserted in the CIFF CTDSM to restore the STF=1 under the ELD effect, maintaining matching simplicity between analog and digital domains. In the CT pipeline converter system, the residue signal VRES is produced by cancellation between continuous-moving input and Fs-clocked DAC output, as shown in Fig. 1. VRES has large and sharp sawtooth edges (originated from the DAC image), which can easily saturate the RA and back-end stage and limits their performance. For pipeline ADC operations (>800MHz BW), RC/LC APF/LPF lattice delays are used in the analog signal path for delay matching, and 1st or 2nd order active LPF was introduced in the RA to suppress the high-frequency DAC image [1]-[3]. The usage of the active RA filtering causes the high-speed DAC current to go through the long route and shunt by the capacitor Cf and the RA (Fig. 1 top), due to the negative feedback action of the RA which tries to maintain a quiet virtual ground. This current increases the wideband linearity requirement of the RA. In our work on CTDSM with a relaxed input bandwidth (160MHz), we propose pre-filtering by placing a passive RC-LPF2 on the QTZ path directly, suppressing the image DAC current from the very beginning of its source. In this way, the DAC high-speed current is shunt by the capacitor C2 of LPF2, and the DAC output signal is filtered before being sent to the RA's virtual ground. Due to the already-presence delay generated by the LPF2 in the QTZ path, we substitute the signal path's lattice delay with a passive RC-LPF1 (Fig. 1 bottom). It aligns the delay of the signal path with the QTZ path, which includes the delay of QTZ1-DAC1 and RC-LPF2. This ensures the accurate removal of the input signal component. Together with the LPF2's pre-filtering, VRES with diminished high-frequency contents and small amplitude is linearity/slew-rate friendly for subsequent RA and the back-end stage, which alleviates the parasitic load and linearity requirements on internal crucial nodes in the GHz-Fs systems [4]. Furthermore, the R1 C1 and R2C2 of LPF1 and LPF2 are correlatively changing over process variation, empowering the delay mismatch compensation in the proposed architecture.

DOI10.1109/CICC60959.2024.10528988
URLView the original
Indexed ByCPCI-S ; EI
Language英語English
Scopus ID2-s2.0-85193926833
Fulltext Access
Citation statistics
Document TypeConference paper
CollectionFaculty of Science and Technology
THE STATE KEY LABORATORY OF ANALOG AND MIXED-SIGNAL VLSI (UNIVERSITY OF MACAU)
INSTITUTE OF MICROELECTRONICS
DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
Corresponding AuthorSin, Sai Weng
Affiliation1.University of Macau, Macao
2.Shanghai Jiao Tong University, China
3.Instituto Superior Tecnico/University of Lisboa, Portugal
First Author AffilicationUniversity of Macau
Corresponding Author AffilicationUniversity of Macau
Recommended Citation
GB/T 7714
Li, Ke,Congzhou, Xianyu,Qi, Liang,et al. A 160MHz-BW 68dB-SNDR 30.8mW Continuous-Time Pipeline DSM with Correlative Passive Low-Pass Filters and DAC Image Pre-Filtering[C]:Institute of Electrical and Electronics Engineers Inc., 2024.
APA Li, Ke., Congzhou, Xianyu., Qi, Liang., Guo, Mingqiang., Martins, Rui P.., & Sin, Sai Weng (2024). A 160MHz-BW 68dB-SNDR 30.8mW Continuous-Time Pipeline DSM with Correlative Passive Low-Pass Filters and DAC Image Pre-Filtering. Proceedings of the Custom Integrated Circuits Conference.
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