Temperature Sensing Circuit Using Segmented Paths
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Solution Overview
Problem
Conventional temperature sensing circuits in semiconductor memory devices face challenges in accurately detecting temperature due to process variations, leading to measurement errors and increased power consumption, particularly in battery-operated systems and high-integration DRAMs.
Innovation Solution
A temperature sensing circuit that generates multiple temperature-dependent voltages with varying levels, compared to a predetermined voltage to output thermal codes, reducing the impact of process variations and circuit size by using a current generating block and voltage mirroring techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional temperature sensing circuit using an operational amplifier and single transistor is used, then the circuit structure is simple, but the temperature measurement accuracy is poor due to process variations
Solution Approach 1:
The temperature sensing circuit is divided into multiple independent sensing paths (first and second sensing paths), each with its own transistor pair and operational amplifier. This segmentation allows the circuit to compensate for process variations by comparing results from multiple paths, thereby improving temperature measurement accuracy while maintaining reasonable circuit complexity through modular design.
Solution Approach 2:
Each sensing path uses transistors with specifically designed different width-to-length ratios (W/L) to create localized variations in current characteristics. The first transistor pair has different W/L ratios between transistors, and the second transistor pair has different W/L ratios, creating local quality differences that enable accurate temperature sensing despite process variations.
2Use of energy by moving object
If the refresh period is increased to reduce power consumption in low temperature regions, then power consumption decreases, but the system requires accurate temperature detection to implement this strategy
Solution Approach 1:
The temperature sensing circuit provides feedback about the actual temperature to the DRAM controller, which uses this information to dynamically adjust the refresh period. The circuit measures temperature accurately using multiple sensing paths with different transistor characteristics, and this temperature information feeds back to optimize the refresh operation timing, thereby reducing power consumption while maintaining data integrity.
3Measurement precision
If multiple temperature-dependent voltages are generated and compared with a predetermined voltage, then temperature detection accuracy improves despite process variations, but the circuit size increases
Solution Approach 1:
The circuit merges multiple temperature sensing functions into a compact integrated structure. Multiple transistor pairs and operational amplifiers are combined in parallel sensing paths that share common circuit elements and layout structures, allowing accurate temperature detection through multiple voltage comparisons while minimizing the overall circuit area through efficient space utilization.
Solution Approach 2:
The circuit uses current mirroring techniques to replicate temperature-dependent currents across multiple paths without proportionally increasing area. By using current mirrors to generate multiple temperature-dependent voltages from shared current sources, the circuit achieves multi-dimensional temperature sensing capability while maintaining compact footprint through efficient current reuse.
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
This approach enhances temperature measurement accuracy and reduces the overall size of the temperature sensing circuit, effectively addressing measurement errors and power consumption issues while maintaining accuracy across varying conditions.
Implementation Method 1
detects temperature based on the fact that a change of a base-emitter voltage (VBE) of a bipolar junction transistor (BJT) is about −1.8 mV/° C.
Implementation Method 2
amplifies the slightly-changing base-emitter voltage (VBE) of the BJT to output the temperature-dependent voltage VTEMP that is in 1:1 correspondence to the temperature
Implementation Method 3
generating a bandgap voltage that is not affected by temperature and supply voltage
Data Source
AI summary
A temperature sensing circuit includes a temperature-dependent voltage generating block configured to generate a plurality temperature-dependent voltages having voltage levels that are changed according to temperature; and a comparing block configured to compare each voltage level of the temperature-dependent voltages with a voltage level of a predetermined voltage to output thermal codes.