BJT Temperature Threshold Circuit With Low-Calibration Digital Output
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Solution Overview
Problem
Conventional temperature detection circuits in integrated circuits (ICs) consume significant silicon area and require part-to-part calibration at multiple temperatures to achieve accuracy, which is costly and time-consuming, especially when monitoring multiple die locations for redundancy.
Innovation Solution
The proposed temperature detection circuitry uses a compact arrangement with bipolar junction transistors (BJTs) and a programmable resistance ratio, implemented using a resistor divider with a finite state machine, to accurately detect temperature thresholds without calibration, minimizing sensitivity to error sources like BJT base current effects and MOSFET mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional temperature detection circuits are used, then temperature detection capability is achieved, but silicon area consumption is significant and calibration requirements are high
Solution Approach 1:
The temperature detection circuit is segmented into distinct functional blocks: a temperature sensing unit using bipolar transistors, a signal processing unit with operational amplifiers, and a digital output stage. This segmentation allows each component to be optimized independently, reducing overall silicon area while maintaining detection accuracy through specialized function allocation.
Solution Approach 2:
The temperature detection circuit is designed to serve multiple functions: it detects temperature thresholds, provides digital output signals for control systems, and operates across various temperature ranges without requiring separate calibration circuits. The universal design eliminates the need for additional calibration components, reducing silicon area while maintaining measurement precision.
2Measurement precision
If conventional temperature detection circuits are used, then temperature monitoring is achieved, but calibration time and cost increase significantly
Solution Approach 1:
The circuit incorporates pre-calibrated reference voltage sources and pre-matched transistor pairs that are factory-calibrated using precise temperature references. This preliminary calibration action eliminates the need for field calibration, reducing calibration time to minimal verification steps while ensuring measurement precision is maintained across operating conditions.
Solution Approach 2:
The temperature detection circuit performs self-calibration through internal reference circuits that automatically compensate for drift and environmental variations. The bipolar transistors and operational amplifiers are designed to self-adjust their operating points, eliminating manual calibration requirements and reducing calibration time while maintaining accurate temperature detection.
3Measurement precision
If temperature detection accuracy is improved through calibration, then measurement precision increases, but device complexity and manufacturing cost increase
Solution Approach 1:
The circuit achieves measurement precision through parameter optimization rather than complex calibration mechanisms. By carefully selecting transistor geometry ratios, resistor values, and operational amplifier gain settings during design, the circuit maintains accurate temperature detection across its operating range without requiring additional calibration components or complex control logic, thus avoiding increased device complexity.
4Reliability
If multiple temperature sensors are deployed for redundancy, then reliability improves, but silicon area consumption increases
Solution Approach 1:
Multiple temperature sensing elements are merged into a single integrated circuit block, sharing common reference voltage sources, signal processing amplifiers, and digital output logic. This merging approach maintains reliability through redundant sensing elements while significantly reducing the total silicon area compared to discrete sensor implementations, as the shared infrastructure eliminates duplicate support circuitry.
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 solution achieves accurate temperature detection with low area cost and minimal calibration requirements, providing a digital detection signal indicating whether the die temperature is above or below a programmed threshold, while reducing sensitivity to error sources and allowing single-temperature calibration for higher accuracy.
Implementation Method 1
a first bipolar junction transistor (BJT) and a second BJT... each having a respective base-emitter voltage that corresponds to a temperature of the substrate
Data Source
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AI summary
An embodiment for an integrated circuit for temperature detection includes: a closed loop circuit branch including: a first bipolar junction transistor (BJT), a first resistor coupled between a first base of the first BJT and a junction node, and an amplifier having an output coupled to the junction node and a non-inverting input coupled to a collector of the first BJT; and an open loop circuit branch including: a second BJT, a second resistor coupled between a base of the second BJT and the junction node, a third resistor coupled between the base of the second BJT and ground, and a comparator having an inverting input coupled to a collector of the second BJT and an output configured to provide a digital voltage signal that corresponds to a temperature reading.