A third-order DT ΔΣ modulator using noise-shaped bidirectional single-slope quantizer

The aspirations for power efficient ADCs have led to many improvements in this area. In delta-sigma modulators, techniques such as VCO-based quantizer [1, 2] and time-domain quantization [3] have been proposed to enhance the overall performance. The former provides additional noise shaping and the latter eliminates the need for the flash ADC. However, in addition to process and temperature variations, the inherent nonlinear behavior of the VCO requires careful attention. The time-domain quantization technique is an efficient way to utilize the quantizer but it does not improve the noise-shaping property. In this paper, we describe modified dual-slope and single-slope ADCs using bidirectional discharging. With a small modification in the discharging phase of these types of ADCs, a first-order quantization noise shaping is attained. These structures may be used as standalone ADCs or as the quantizer in a delta-sigma loop. Moreover, because the modified discharging extracts the quantization error in the analog domain, possibilities exist for further performance improvements [4].

[1]  Gabor C. Temes,et al.  A Noise-Coupled Time-Interleaved ΔΣ ADC with 4.2MHz BW, -98dB THD, and 79dB SNDR , 2008, 2008 IEEE International Solid-State Circuits Conference - Digest of Technical Papers.

[2]  M.Z. Straayer,et al.  A 12-Bit, 10-MHz Bandwidth, Continuous-Time $\Sigma\Delta$ ADC With a 5-Bit, 950-MS/s VCO-Based Quantizer , 2008, IEEE Journal of Solid-State Circuits.

[3]  Min C. Park,et al.  A 0.13µm CMOS 78dB SNDR 87mW 20MHz BW CT ΔΣ ADC with VCO-based integrator and quantizer , 2009, 2009 IEEE International Solid-State Circuits Conference - Digest of Technical Papers.

[4]  Matthew Park.  A 0.13[mu]m CMOS 78dB SNDR 87mW 20MHz BW CT [Delta Sigma] ADC with VCO-based integrator and quantizer , 2009 .

[5]  Edgar Sánchez-Sinencio,et al.  A 20MHz BW 68dB DR CT ΔΣ ADC based on a multi-bit time-domain quantizer and feedback element , 2009, 2009 IEEE International Solid-State Circuits Conference - Digest of Technical Papers.