PTAT Temperature Sensor Circuit for Mismatch-Insensitive CMOS Sensing
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Solution Overview
Problem
Conventional CMOS-based temperature sensors are prone to inaccuracies due to process variations and component mismatches, which complicates calibration and increases production costs.
Innovation Solution
A temperature sensor design that utilizes a PTAT voltage generator, sampling and gain boosting circuit, and filter, with a controller managing current sources and timing signals, to produce a voltage insensitive to process variations and mismatches, achieving accurate temperature measurements by averaging multiple sampling voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional CMOS-based temperature sensors are used, then the sensor can be integrated into smart devices using traditional CMOS process, but the sensor accuracy deteriorates due to process variation and component mismatch
Solution Approach 1:
The patent uses multiple copies of the same diode and current source structures (e.g., first diode and second diode with identical configurations, multiple current sources I1-I4) to create redundant measurement paths. By copying the same circuit topology and measuring the same physical quantity through multiple identical structures, the system can average out process variations and mismatch effects, thereby maintaining accuracy while using standard CMOS processes.
Solution Approach 2:
The patent measures voltage at different current levels (by enabling different combinations of current sources I1-I4) to obtain multiple sampling voltages. By changing the operating parameters (current magnitude) and measuring at multiple points, the system can differentiate between temperature-dependent effects and process variation effects, allowing accurate temperature extraction through mathematical processing that eliminates mismatch errors.
2Measurement precision
If multiple sampling voltages are taken to improve accuracy, then temperature measurement precision improves, but device complexity increases due to additional current sources and control circuitry
Solution Approach 1:
The patent divides the measurement process into multiple discrete sampling steps, where different subsets of current sources are enabled in sequence (e.g., I1+I2, I2+I3, I3+I4, I4+I1 combinations). Each sampling voltage corresponds to a specific segmented measurement phase controlled by phase signals. This segmentation allows the complex multi-point measurement to be broken down into manageable, sequentially executed steps that can be controlled by simple timing logic.
Solution Approach 2:
The patent employs periodic switching of current sources controlled by phase signals (PHASE0-PHASE3) to sequentially enable different current combinations. The controller periodically cycles through different sampling configurations in a repeating sequence, taking multiple measurements over time. This periodic action transforms a potentially complex simultaneous multi-parameter measurement into a time-sequenced measurement process, reducing circuit complexity while maintaining measurement precision.
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 provides accurate temperature readings within 1.5° C across a range of process variations with a single calibration, simplifying the calibration process and reducing production costs.
Implementation Method 1
The PTAT voltage generator utilizes a plurality of current sources, each of which is in electrical communication with the same diode, or diode stack
Data Source
AI summary
A temperature sensor that is insensitive to process variation and mismatch is disclosed. The temperature sensor includes a PTAT voltage generator, a sampling and gain boosting circuit, a filter and a controller. The PTAT voltage generator utilizes a plurality of current sources, each of which is in electrical communication with the same diode, or diode stack. The output of the PTAT voltage generator is sampled and amplified with the sampling and gain boosting circuit. The output of the sampling and gain boosting circuit is then filtered using a low pass filter. The selection of the current mirrors, the sampling timing and other signals are provided by the controller. In some simulations, the output from the temperature sensor was accurate to within 1.5° C., using a one temperature calibration process.