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A Temperature – and Supply- Variation Robust 2nd-Order Sigma-Delta Modulation for Capacitive Sensing

A Temperature – and Supply- Variation Robust 2nd-Order Sigma-Delta Modulation for Capacitive Sensing
Jaewoong Kim
DGIST Authors
Kim, Jaewoong; Je, Minkyu; Lee, Junghyup
Minkyu Je
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Capacitance to digital converter, VCO quantizer, Sigma-Delta modulation, Supply variation, temperature variation
In this paper, I proposed a temperature- and supply variation robust 2nd-order sigma-delta modulation circuit for capacitive sensing. Capacitive sensing by conventional circuits is basically supply sensitive. Capacitance is sensed by reading the charge that is equal to the difference between the capacitance value of the capacitor and the capacitor to be sensed. In this method, the amount of charge is dependent on the supply, so it is insensitive to supply variation. In this paper, the capacitance is read by using the time determined by the discharge characteristics when a capacitor called T0V meets the resistance component. The charge accumulated in the capacitor is certainly influenced by the supply value, but capacitive sensing is performed using the characteristic that the time taken to discharge the charge to zero is always constant. In the process, VCO (Voltage-Controlled-Oscillator) based ADC (Analog-to-Digital Converter) was used to increase the resolution by utilizing the noise shaping effect of sigma-delta ADC. In the process, the resistor is switched to a switched capacitor to obtain robust characteristics against temperature variations. Unlike resistance whose values change with temperature, capacitance are relatively robust to temperature effects. By using the characteristics, a circuit having robust characteristics in temperature variation as well as robust in supply variation.
Table Of Contents
Abstract i List of contents iii List of figures iv List of figures v Ⅰ. Introduction 1.1 Motivation and Objective 1 1.2 Theses outline 3 ⅠI. Supply- Variation Robust 2nd-Order Sigma-Delta Modulation 2.1 Supply Independent Technique 4 2.2 Injection Locking Current Controlled Oscillator 8 2.3 VCO Based ADC 13 2.4 Full Architecture 16 2.4.1 Control Block 19 2.4.2 Block Diagram 21 2.5 Schematic and Layout 23 III. Temperature- and Supply- Variation Robust 2nd-Order Sigma-Delta Modulation 3.1 Switched Capacitor DAC 31 3.2 Switched Capacitor Clock Generator 36 3.3 Control Block 38 3.4 Schematic 39 IV. Simulation and Measurement Result 4.1 Resistor DAC Circuit 42 4.1.1 Measurement Result 42 4.2 Switched Capacitor DAC Circuit 45 4.2.1 Simulation Result 45 V. Conclusion
Information and Communication Engineering
Related Researcher
  • Author Lee, Junghyup Integrated Nano-Systems Laboratory
  • Research Interests Analog and Mixed Signal IC Design; Smart Sensor Systems; Bio-medical ICs and Body Channel Communication Systems
Department of Information and Communication EngineeringThesesMaster

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