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

作者：Maghari Nima^*; Moon Un Ku

来源：IEEE Journal of Solid-State Circuits, 2011, 46(12): 2882-2891.

DOI：10.1109/JSSC.2011.2164964

• Analog-to-digital conversion
• CMOS analog integrated circuits
• delta-sigma modulation
• switched-capacitor circuits
• time-based quantization

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 mu 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.

• 出版日期2011-12