Resistor-based Temperature Sensors in CMOS Technology

Acknowledgments
Contents
About the Author
Chapter 1: Introduction
	1.1 Temperature Sensor Applications and Specifications
	1.2 Challenges in Frequency Reference Compensation
	1.3 Resolution and Resolution FoM
	1.4 CMOS Temperature Sensing Elements and Their Theoretical Resolution FoMs
		1.4.1 Bipolar Junction Transistors (BJTs)
		1.4.2 MOSFETs
		1.4.3 Electro-thermal Filters (ETFs)
		1.4.4 Resistors
	1.5 Choice of the Sensing Element
	1.6 Goals and Book Organization
	References
Chapter 2: Sensor and Readout Topologies
	2.1 Introduction
	2.2 Sensor Design
		2.2.1 Sensing Resistors
		2.2.2 Impedance Reference
			2.2.2.1 Reference Choices
			2.2.2.2 Comparison
		2.2.3 Sensor Structures and Readout Method
			2.2.3.1 Dual-R Sensors
			2.2.3.2 RC Sensor Structures
			2.2.3.3 RC Filter Readout
	2.3 ADC Choice
		2.3.1 Nyquist Versus Oversampled ADCs
		2.3.2 Continuous-Time ΔΣ-ADC
	2.4 Concluding Remarks
	References
Chapter 3: Wien Bridge–Based Temperature Sensors
	3.1 Introduction
	3.2 General Design Choices
		3.2.1 WB Sensor
		3.2.2 Phase-Domain ADC
			3.2.2.1 Phase Detector
			3.2.2.2 Phase DAC and Phase-Domain ΔΣ-ADC
		3.2.3 System Analysis
			3.2.3.1 Resolution and FoM
			3.2.3.2 Nonlinearity and Trimming
	3.3 Implementation I, Proof of Concept
		3.3.1 Circuit Implementation
			3.3.1.1 Chopper and Chopper Merging
			3.3.1.2 Amplifier Design
		3.3.2 Measurement Results
			3.3.2.1 Resolution and FoM
			3.3.2.2 Calibration and Inaccuracy
			3.3.2.3 Plastic Packaging
			3.3.2.4 Batch-to-Batch Spread
			3.3.2.5 Comparison with Prior Art
	3.4 Implementation II, Reduced Chip Area
		3.4.1 Circuit Implementation
		3.4.2 Measurement Results
			3.4.2.1 Resolution and FoM
			3.4.2.2 Calibration and Inaccuracy
			3.4.2.3 Comparison to Implementation I
	3.5 Implementation III, Better Accuracy and Stability
		3.5.1 Circuit Implementation
		3.5.2 Measurement Results
			3.5.2.1 Resolution and FoM
			3.5.2.2 Calibration and Inaccuracy
			3.5.2.3 Comparison to Implementation II
	3.6 Comparisons and Concluding Remarks
	References
Chapter 4: Wheatstone Bridge–Based Temperature Sensors
	4.1 Introduction
	4.2 General Design Choices
		4.2.1 Traditional Readout Versus Direct Readout
		4.2.2 Nonlinearity and Trimming
	4.3 Implementation I, Proof of Concept
		4.3.1 Circuit Implementation
		4.3.2 Measurement Results
			4.3.2.1 Calibration and Inaccuracy
			4.3.2.2 Resolution and FoM
			4.3.2.3 Comparison with Prior Art
	4.4 Implementation II, Smaller Area and Better FoM
		4.4.1 System-Level Design
		4.4.2 Circuit Implementation
			4.4.2.1 Wheatstone Bridge and DAC
			4.4.2.2 Zoom ADC
			4.4.2.3 Nonlinearity and Segment Averaging
		4.4.3 Measurement Results
			4.4.3.1 Calibration and Inaccuracy
			4.4.3.2 Resolution and FoM
			4.4.3.3 Comparison to Implementation I
	4.5 Implementation III, Even Smaller Area and Better FoM
		4.5.1 System-Level Design
		4.5.2 Circuit Implementation
		4.5.3 Measurement Results
			4.5.3.1 Calibration and Inaccuracy
			4.5.3.2 Resolution and FoM
			4.5.3.3 Comparison to Implementation II
	4.6 Implementation IV, Approaching the FoM Limit
		4.6.1 Architecture and Design Considerations
			4.6.1.1 RDAC Switching Scheme
			4.6.1.2 DAC Array and DAC Range Optimization
			4.6.1.3 Integrator Nonlinearity
		4.6.2 Linearized OTA Design
			4.6.2.1 Linearization Principle
			4.6.2.2 Biasing Generation
			4.6.2.3 Circuit Structure
			4.6.2.4 Nonlinearity Simulation Results
			4.6.2.5 Power Scaling and System-Level Simulation
		4.6.3 Circuit Implementation
		4.6.4 Measurement Results
			4.6.4.1 Calibration and Inaccuracy
			4.6.4.2 Resolution and FoM
			4.6.4.3 Comparison to Implementation III
	4.7 Comparison and Concluding Remarks
	References
Chapter 5: Application-Driven Designs
	5.1 Introduction
	5.2 A Low-Power Sensor for Biomedical Applications
		5.2.1 Background Introduction
		5.2.2 Circuit Implementation
			5.2.2.1 Wheatstone Bridge and Series DAC
			5.2.2.2 PWM-Assisted Trim
			5.2.2.3 Return-to-Zero DAC and DSM Readout
		5.2.3 Measurement Results
			5.2.3.1 Calibration and Inaccuracy
			5.2.3.2 Resolution and FoM
			5.2.3.3 Supply and Clock Sensitivity
			5.2.3.4 Power-Down Mode
			5.2.3.5 Comparison to Previous Work
		5.2.4 Summary
	5.3 A Wheatstone Bridge Sensor Embedded in a RC Frequency Reference
		5.3.1 Background Introduction
		5.3.2 Circuit Implementation
			5.3.2.1 Circuit Principle
			5.3.2.2 Reconfigurable RC Network and ADC
		5.3.3 Measurement Results
			5.3.3.1 Calibration and Inaccuracy
			5.3.3.2 Resolution and FoM
			5.3.3.3 Frequency Reference
			5.3.3.4 Comparison to Previous Work
		5.3.4 Summary
	5.4 Concluding Remarks
	References
Chapter 6: Conclusions and Outlook
	6.1 Main Findings
	6.2 Temperature Sensor Comparison
	6.3 Systematic Design Approaches for Accuracy
		6.3.1 Cadence Modeling
		6.3.2 Data Analysis
		6.3.3 Experimental Verification
	6.4 More Future Research Directions
		6.4.1 Area- and Power-Efficient Digital Backend
		6.4.2 Background Calibration of Wheatstone Bridge Sensors
		6.4.3 Long-Term Stability of Wien Bridge Sensors
		6.4.4 Energy-Efficient Wheatstone Bridge Temperature Sensors with Scaled Energy/Conversion
		6.4.5 Applications of the Tail-Resistor Linearized OTA
	6.5 Concluding Remarks
	References
Appendix A
	A.1 Measurement Setup
	A.2 OTA with Tail-Resistor Linearization: Condition of the 3rd-Order Nonlinearity Cancellation
Index