A 4GHz 3 rd order continuous-time ∆Σ ADC is presented with a loop filter topology that absorbs the pole caused by the input capacitance of its 4-bit quantizer and also compensates for the excess delay caused by the quantizer's latency. The ADC was implemented in 45nm-LP CMOS and achieves 70dB DR and −74dBFS THD in a 125MHz BW, while dissipating 260mW from 1.1/1.8V supply. The ADC occupies 0.9mm 2 including the modulator, clock circuitry and decimation filter. Index Terms Analog-to-digital conversion, oversampling ADCs, CMOS analog integrated circuits, continuoustime sigma-delta modulation, delta-sigma modulator, continuous-time filters, multi-bit, wireless communication, radio receivers, base stations. I. INTRODUCTION Analog-to-Digital converter (ADC) developments are driven by the increasing demand for signal bandwidth and dynamic range in applications such as wireline and wireless communications, medical imaging and high-definition video processing. Multi-channel applications such as digital FM (DFM) and LTE-advanced require ADCs whose signal bandwidth ranges from 20MHz-100MHz and whose dynamic range (DR) is greater than 70dB [1]-[3]. To achieve high data rates, these applications rely on advanced digital modulation techniques that can be

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In this paper, a high-speed continuous-time (CT) ΔΣ ADC topology is proposed that absorbs the pole normally caused by the quantizer's input capacitance, while a local feedback loop compensates for the quantizer's excess delay. These measures allow a high-resolution multi-bit ΔΣ ADC to operate at GHz sampling rates. The bandwidth of this CMOS ΔΣ ADC is 6× wider than the state-of-the-art [1, 2]. Compared to a state-of-the-art pipeline BiCMOS ADC [3], it achieves similar power efficiency and bandwidth, but it only occupies 0.9mm 2 in 45nm CMOS, which is essential for low-cost integration. The 4b 3 rd -order CT ΔΣ ADC is sampled at 4GHz and achieves 70dB DR and -74dBFS THD in a 125MHz BW while consuming 256mW. This prototype enables the use of ΔΣ ADCs in applications such as GSM base-stations and HD video systems.

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