Low Voltage Bandgap Temperature Sensor for ICs
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Solution Overview
Problem
Existing temperature sensors in integrated circuits face challenges in efficiently measuring temperature variations across dies while minimizing power consumption and being independent of voltage and process variations, which is crucial for extending battery life in mobile devices.
Innovation Solution
The development of low voltage bandgap temperature sensors using diode-connected bipolar junction transistors with operational amplifiers to separate PTAT and CTAT currents, allowing for efficient temperature measurement with reduced power dissipation and operation in multi-voltage domains, integrated into autonomous multiprobe measurement devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional temperature sensors are used in integrated circuits, then temperature measurement capability is provided, but power dissipation increases and battery life decreases
Solution Approach 1:
The patent changes the operating voltage parameter of the temperature sensor to ultra-low voltage levels. The bandgap sensor is designed to operate at voltages significantly lower than conventional sensors, directly reducing power dissipation while maintaining temperature measurement functionality through careful circuit design that compensates for lower operating voltage
Solution Approach 2:
The temperature sensor is designed to operate autonomously without requiring external processor intervention or complex support circuits. The sensor performs self-calibration and self-measurement functions, reducing the resource consumption of other subsystems and minimizing overall power requirements while providing continuous temperature monitoring
2Temperature
If conventional temperature sensors are used, then temperature tracking is provided, but sensitivity to voltage and process variations affects measurement accuracy
Solution Approach 1:
The patent employs parameter changes by utilizing the inherent temperature dependence of base-emitter voltages in bipolar transistors. By measuring the difference in base-emitter voltages between two transistors operating at different current densities, the sensor creates a PTAT (proportional to absolute temperature) signal that is inherently insensitive to voltage and process variations, as this voltage difference directly tracks temperature
Solution Approach 2:
The patent implements feedback mechanisms where operational amplifiers continuously monitor and compare voltage signals from the transistor network. The feedback loops adjust operating points and compensate for drift, ensuring that the temperature measurement remains accurate despite variations in supply voltage or manufacturing process parameters. The feedback ensures stable operation and maintains measurement reliability
3Productivity
If autonomous operation is implemented, then resource consumption of other subsystems is reduced, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the temperature sensor itself. The sensor integrates temperature measurement, self-calibration, and autonomous control capabilities within a single compact circuit block. By combining these functions, the sensor eliminates the need for separate processor interventions and external control circuits, reducing overall system resource consumption while the integrated nature keeps complexity manageable
Solution Approach 2:
The temperature sensor is designed with universal functionality that allows it to operate independently across different voltage domains and clocking schemes. The sensor can adapt to various operating conditions and provides multiple outputs (temperature data, status flags, calibration information) that can be used by different system components, reducing the need for specialized subsystems and lowering overall system complexity
4Area of stationary object
If footprint reduction is achieved, then integration density increases, but sensor functionality may be compromised
Solution Approach 1:
The patent segments the temperature sensor into functional blocks that can be efficiently laid out on the chip. The sensor is divided into transistor pairs, operational amplifier stages, and signal processing sections that can be compactly arranged. This segmentation allows for optimized placement and routing, reducing the overall footprint while ensuring each functional block maintains its required performance characteristics
Solution Approach 2:
The patent employs nesting by placing smaller functional elements within larger structure. For example, the sensor core is nested within a compact layout that shares peripheral circuits and signal paths with other on-chip components. This nested arrangement maximizes the use of available chip area, reducing the sensor's footprint while maintaining full functionality through shared resources and efficient spatial utilization
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 solution enables reduced power consumption and resource usage, allowing for accurate temperature tracking across integrated circuits with minimal impact on battery life and improved performance in mobile devices.
Implementation Method 1
a PTAT (proportional to absolute temperature) current flows through the first resistor
Implementation Method 2
a CTAT (complementary to absolute temperature) current flows through the second resistor
Implementation Method 3
a bandgap sensor which measures temperatures within an integrated circuit
Data Source
AI summary
A bandgap sensor which measures temperatures within an integrated circuit is presented. The sensor may include a first transistor having an emitter node coupled in series to a first resistor and a first current source, wherein a PTAT current flows through the first resistor, and a second transistor having a base node coupled to a base node of the first transistor, and a collector node coupled to a collector node of the first transistor, further wherein the first and second transistors are diode connected. The sensor may further include a first operational amplifier providing negative feedback to the first current source, wherein the negative feedback is related to a difference in the base-emitter voltages of the first and second transistors, and a second operational amplifier which couples the base-emitter voltage of the second transistor across a second resistor, wherein a CTAT current flows through the second resistor.