A Dual-Mode Compatible CT ADC With FIR DAC and SB Quantization for DSM and IDSM Operations
This paper presents a continuous-time (CT) ADC capable of operating as either a delta-sigma modulator (DSM) or an incremental DSM (IDSM). To address the high jitter sensitivity inherent to oversampled CT systems, an architecture incorporating FIR DACs and a single-bit (SB) quantizer is adopted. A fu...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IEEE
2025-01-01
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| Series: | IEEE Access |
| Subjects: | |
| Online Access: | https://ieeexplore.ieee.org/document/11062919/ |
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| Summary: | This paper presents a continuous-time (CT) ADC capable of operating as either a delta-sigma modulator (DSM) or an incremental DSM (IDSM). To address the high jitter sensitivity inherent to oversampled CT systems, an architecture incorporating FIR DACs and a single-bit (SB) quantizer is adopted. A fully numerical loop parameter extraction method based on the least-mean-square (LMS) algorithm is proposed, eliminating the need for tedious algebraic derivations required in conventional approaches. Additionally, a multirate state-space simulation framework is introduced to address compatibility issues arising from excess loop delay (ELD), which conventional approaches fail to adequately handle. At the circuit level, a compact and energy-efficient compensation FIR DAC is implemented based on a configurable capacitive passive summation network. The main FIR DAC with 8 taps employs a Zapped Virtual-Ground-Switched Dual Return-To-Open (DRTO) topology to suppress ISI and the effects of limited reference impedance. Layout asymmetry in the main FIR DAC induces differential-mode (DM) crosstalk, which is alleviated through a layout-level cancellation technique leveraging even-indexed FIR taps. The prototype, fabricated in a TSMC 65 nm LP CMOS process with a core area of 0.235 mm2, achieves SNDRpeak of 84.3 dB and 81.3 dB in DSM and IDSM modes, respectively, over a 100 kHz bandwidth. Powered by a single 1.2 V supply, it consumes <inline-formula> <tex-math notation="LaTeX">$269~\mu $ </tex-math></inline-formula>W and <inline-formula> <tex-math notation="LaTeX">$277~\mu $ </tex-math></inline-formula>W in DSM and IDSM modes, corresponding to FoMSNDR of 170 dB and 166.9 dB. |
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| ISSN: | 2169-3536 |