A Third-Order DT $\Delta\Sigma$ Modulator Using Noise-Shaped Bi-Directional Single-Slope Quantizer

Abstract

This paper describes a new analog-to-digital converter based on the traditional dual-slope ADC operation. With a small modification to the discharging phase of the dual-slope ADC, first-order quantization noise shaping is achieved. This quantizer is used in a second-order loop filter and results in an overall third-order quantization noise shaping. To remove the need for any extra active element, this quantizer is merged with the active adder. In this fashion, the multi-bit flash ADC is removed and hence the loading of the active-adder is reduced to a single continuous-time comparator. Furthermore, to alleviate the speed of the counting-clock and the common-mode biasing accuracy requirements, a bi-directional discharging scheme is proposed. As a proof of concept, the second-order loop filter with the proposed quantizer is fabricated in a 0.18 m CMOS technology and achieves over 78 dB SNDR with an oversampling ratio of 24 and 50 MHz sampling speed. The power consumption is 2.9 mW from a 1.5 V power supply.

Time-interleaved integrating quantizer incorporating channel coupling for speed and linearity enhancement

“…As a result, the conversion speed is decoupled from the input dynamic range; a faster sample rate is achieved. A sophisticated bi-directional discharge scheme [7] can be avoided; instead a uni-directional discharge is used for dual-slope operation without the distortion penalty. It should be noted that the integrator output is scrambled, and that could be made further insignificant by the noise shaped quantization error if noise coupling [3] is further introduced or a higher order loop filter is cascaded.…”

“…In [1]- [2], an integrating quantizer based on modified discharge phase is presented to introduce a firstorder quantization noise shaping. Despite the increased effective bandwidth from advantageous noise shaping, the structure is limited to low or medium bandwidth.…”

A 4th-Order Low-distortion Low-pass Modulator Using Timing-Sharing Technique

“…Capacitive input feed-forward (CIF) methodology is to create only input feed-forward path to the input of last integrator of loop filter. Then move the input feed-forward path at the quantizer input to the input of the last integrator and multiplies the input feed-forward 1 …”

“…With the development of CMOS process with the increasing sampling rate, bandwidth of sigma-delta modulator is growing and has become one of the choices for widebandwidth high-resolution wired and wireless communications [1,2]. To achieve high resolution and linearity, 1MHz bandwidth and 12bit resolution, it is a more challenging work.…”

Sturdy-MASH delta-sigma modulator with noise-shaped integrating quantizer and dual-DAC DWA

“…In this paper, a new SMASH delta-sigma modulator is presented which utilizes a noise-shaped integrating quantizer (NSIQ) [5] to overcome the abovementioned issues. Using the noise-shaped integrating quantizer in both loops not only increases the noise-shaping order by a factor of one, but it also allows extracting the quantization error of the first loop without any extra hardware.…”