An Adaptive-Resolution Quasi-Level-Crossing Delta Modulator With VCO-Based Residue Quantizer

Abstract

This brief introduces an adaptive-resolution (AR) quasi-level-crossing delta modulator ADC with a voltagecontrolled oscillator (VCO)-based residue quantizer for Internetof-Things (IoT) wireless sensor nodes. The residue voltage signal is digitized by a VCO-based residue quantizer, thus leading to a straightforward implementation of level-crossing (LC) and AR algorithms in digital domain. The inherent and mismatch-induced dithering provided by the VCO-based residue quantizer increases the proposed modulator's dynamic range and average sampling rate for slowly-varying input signals, enabling accurate sampling and conversion. For fast-varying signals, the AR algorithm is adopted to reduce the average sampling rate by a factor of three compared to the straightforward LC algorithm at the edge of the modulator's signal bandwidth. Fabricated in 28-nm CMOS, the proposed modulator achieves a peak SNDR of 53 dB over a signal bandwidth of 1.78 MHz.

A Deep-Subthreshold Variation-Aware 0.2-V Open-Loop VCO-Based ADC

“…Nonetheless, most of such solutions are not portable to ULV supply (<0.3 V). In the popular closed-loop configuration, the VCO and digital circuitry act as a multi-bit quantizer (frequencybased) [18], [19] or perform voltage-to-phase integration and quantization (phase-based) [20] within the delta-sigma () modulator loop. The large loop gain suppresses the V -tof nonlinearity and allows increasing the order of the loop filter for more aggressive in-band noise shaping.…”

Dickson-Charge-Pump-Based Voltage-to-Time Conversion for Time-Based ADCs in 28-nm CMOS

“…In our previous work [17], we use a Dickson charge pump (CP) as a VTC but the system still needs a multitude of VTCs to overcome the non-linearity of the generated ramp signal. Event-based ADC in [18] can reduce the system sampling rate and power consumption but still requires analog comparators of high performance.…”

The Complex Adaptive Delta-Modulator in Sliding Mode Theory

“…Over the last few years, the quantizers and modulators have gain popularity due to their important role in many engineering fields including measurement, instrumentation, power converters and analog to digital conversion (ADC) [ 1 , 2 ]. In particular, the binary quantizers including delta modulators ( -Ms) and delta sigma modulators ( -Ms) are widely utilized in power conversions for their implementation simplicity [ 3 , 4 ], networked and quantized control systems for their low-data rate [ 5 , 6 ], and as typical complex systems for their high nonlinearity, periodicity and robustness at the same time [ 7 , 8 ].…”