Design of a high-precision third-order NS SAR ADC for audio applications

doi:10.3969/j.issn.1000-5641.2026.02.011

Abstract

Abstract:

This paper proposes the design of a high-precision third-order noise-shaping (NS) successive approximation register (SAR) analog-to-digital converter (ADC) for audio applications. The NS effect of passive NS circuits deteriorates owing to gain loss. In response, a cascaded integral feed-forward (CIFF) active NS loop is designed. To mitigate the impact of integrator nonlinearity on the ADC, a primary-auxiliary dual-path high-linearity source follower structure is proposed. This source follower buffers the residual voltage onto the integration capacitor, ultimately achieving third-order NS performance. A mismatch error shaping (MES) technique is incorporated to mitigate nonlinearities induced by digital-to-analog converter (DAC) mismatches. Fabricated in a 55 nm CMOS process, the ADC core occupies approximately 0.25 mm². Post-layout simulation results demonstrate that under a 1.8 V supply voltage at 40℃, while operating at a sampling frequency of 8 MS/s with a bandwidth of 125 kHz and consuming 10.83 mW of power, the ADC achieves an effective number of bits (ENOB) of 15.14 and a signal-to-noise and distortion ratio (SNDR) of 92.92 dB with a Schreier figure of merit (FoM_S) of 163.54 dB.

Key words: NS SAR ADC, source follower, capacitor stacking, ping-pong architecture, MES

CLC Number:

TN43

Nannan GENG, Jikun WANG, Shouxiang HAN, Chunqi SHI. Design of a high-precision third-order NS SAR ADC for audio applications[J]. J* E* C* N* U* N* S*, 2026, 2026(2): 117-127.

Figures/Tables 15

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Table 1

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参考文献	工艺/nm	面积/mm²	结构	带宽/kHz	OSR	功耗/mW	SNDR/dB	FoM_S/dB
VLSI 2017^[12]	180	3.87	Pipe, SAR	100	1	11.35	100	179.9
VLSI 2019^[13]	180	2.85	SDCT	250	64	24	103.5	173.7
JSSC 2022^[14]	180	1.1	SD	250	96	17.7	103.2	174.7
TCAS-Ⅱ 2022^[15]	180	1.2	SD	576	14	7.2	94.45	173.4
VLSI 2022^[16]	40	0.48	NS SAR	100	64	2	98.3	175.3
ICTA 2023^[17]*	180	–	NS SAR	250	10	3.76	97.15	175.3
VLSI 2024^[18]	180	0.725	SDCT	200	128	2.52	93.8	169.8
This work*	55	0.25	NS SAR	125	32	10.83	92.92	163.54

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