Design of Digital-Differentiator-Embedded Continuous-Time Delta-Sigma Modulator and Bandgap-Reference-Free Resistor-Based Temperature Sensor
Date Issued
2011
Date
2011
Author(s)
Chan, Wei-Shan
Abstract
This thesis consists of two parts: PART1 presents a continuous-time delta-sigma modulator with a digital differentiator for the purpose of excess loop compensation and reducing the number of digital-to-analog converter (DAC) element to solve the DAC nonlinearity issue. PART2 presents a bandgap-reference-free resistor-based temperature sensor for the purpose of relaxing the complexity of the design of front-end circuits, and furthermore, operating in high-speed and low-power environments.
Low-pass structure has been widely used in continuous-time delta-sigma modulator. The approaches to improve signal-to-noise ratio (SNR), first, is increasing over-sampling ratio (OSR) to reduce in-band noise power, however, high OSR results in high operation speed and more power consumption. Also, the excess loop delay issue may even worse. Second, increasing the order of loop filter can also improve SNR, but stability and power consumption are still the major problems. Another way to improve SNR is using a multi-bit quantizer, but the nonlinearity of multi-bit DAC is a challenge.
Above all, we proposed a multi-bit delta-sigma modulator with a digital differentiator to compensate excess loop delay effect and largely reduce the number of DAC elements to solve the nonlinearity issue. The 2nd-oder 4-bit continuous-time (CT) delta-sigma modulator (DSM) is implemented in TSMC 0.18-um 1P6M process, this work can achieve resolution of 0.125°C, the temperature range is -40°C~120°C, core area is 0.23 mm2, and power consumption is 36 uW under 1.8-V power supply.
Subjects
Continuous-time Delta-sigma Modulator
Temperature Sensor
Type
thesis
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