Hybrid Reverse Bandgap Reference for Low-Power Temperature Sensing
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Solution Overview
Problem
Existing bandgap reference (BGR) and digital temperature sensor (DTS) circuits in integrated circuits face challenges in achieving low power and low cost while maintaining accuracy and efficiency, particularly in portable devices, due to large footprints, high power consumption, and complex trimming methodologies.
Innovation Solution
A low power hybrid reverse (LPHR) BGR/DTS circuit utilizing subthreshold metal oxide semiconductor (MOS) transistors and a parasitic PNP BJT device, which allows for a configurable BGR or DTS operation with a linear transfer function, using an unbalanced amplifier and scaled emitter-base voltages to achieve high accuracy and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional BGR and DTS circuits are used, then measurement precision and reliability are maintained, but power consumption is high and device area is large
Solution Approach 1:
The patent combines BGR and DTS functions into a single hybrid circuit that shares common components (amplifier, resistors, transistors, emitter-base voltage generation). This merging reduces total power consumption and device area while maintaining both reference voltage generation and temperature measurement capabilities with high accuracy through shared high-performance analog components.
Solution Approach 2:
The hybrid circuit serves multiple functions: generating accurate bandgap reference voltage, measuring temperature with high precision, and providing both analog and digital outputs. The same core circuitry (amplifier, emitter-base voltage source, resistor network) supports both BGR and DTS operations, eliminating the need for separate dedicated circuits and reducing overall power consumption.
2Area of stationary object
If traditional BGR and DTS circuits are used, then measurement precision and reliability are maintained, but device area is large
Solution Approach 1:
The patent combines BGR and DTS functions into a single hybrid circuit that shares common components (amplifier, resistors, transistors, emitter-base voltage generation). This merging reduces total device area while maintaining both reference voltage generation and temperature measurement capabilities with high accuracy through shared high-performance analog components.
Solution Approach 2:
The DTS functionality is nested within the BGR circuit structure. The temperature sensor uses the same amplifier, emitter-base voltage source, and resistor network that form the core of the bandgap reference circuit. This nesting allows both functions to coexist in a compact footprint without requiring separate dedicated components for each function.
3Measurement precision
If complex trimming methodologies are used, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The circuit uses self-generated emitter-base voltages from parasitic PNP transistors as internal reference signals for comparison. The bandgap reference voltage and temperature-dependent voltages are automatically generated by the circuit's own components (resistors, transistors, amplifier) without requiring external trimmable references or complex calibration circuits, reducing manufacturing complexity while maintaining precision.
Solution Approach 2:
The patent replaces complex mechanical trimming mechanisms with electronic voltage comparison and digital code generation. Instead of using trimmable capacitors or resistors requiring manual adjustment, the circuit uses an amplifier to compare voltages and a successive approximation register to generate digital temperature codes automatically, simplifying manufacturing while maintaining high measurement accuracy.
4Loss of time
If traditional DTS circuits are used, then temperature measurement is provided, but conversion time is long
Solution Approach 1:
The circuit employs a successive approximation register that operates in periodic cycles to convert analog voltage comparisons into digital temperature codes. The systematic bit-by-bit approximation process efficiently converges to the final digital value in minimal cycles, reducing conversion time while maintaining high precision through the structured periodic search algorithm.
Solution Approach 2:
The patent replaces slow analog-to-digital conversion mechanisms with a faster successive approximation approach using digital logic. The SAR circuit systematically tests voltage thresholds and generates digital codes through logical comparisons rather than slow ramping or integration methods, achieving both high precision and fast conversion by substituting electronic/digital processes for traditional conversion mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The LPHR circuit achieves a 38% larger temperature range with 25% less power and 23% shorter conversion time, providing a linear code-to-temperature transfer function with high accuracy and improved power supply rejection ratio (PSRR) performance.
Implementation Method 1
low power hybrid reverse (LPHR) BGR/DTS circuit utilizing subthreshold metal oxide semiconductor (MOS) transistors and a parasitic PNP BJT device
Implementation Method 2
A BGR provides an accurate voltage source which may be used as reference for internal power supply generation or as a bias voltage for critical circuits
Implementation Method 3
generate a proportional-to-absolute-temperature (PTAT) voltage (Vptat) and a complementary-to-absolute-temperature (CTAT) voltage (VEB)
Implementation Method 4
analog-to-digital converter (ADC) is added to perform the comparison and thus implement the DTS function
Implementation Method 5
successive approximation register (SAR) logic circuit to generate digital codes representative of the temperature
Data Source
AI summary
A low power hybrid reverse (LPHR) bandgap reference (BGR) and digital temperature sensor (DTS) or a digital thermometer, which utilizes subthreshold metal oxide semiconductor (MOS) transistors.