Delta-VBE Temperature Sensing with Digital Curvature Correction
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Solution Overview
Problem
Existing temperature sensors using bipolar junction transistors (BJTs) face challenges in achieving high accuracy due to limitations in analog-to-digital converter (ADC) resolution, ADC headroom, and nonlinearity of base-emitter voltage curvature, leading to inaccuracies in temperature measurement.
Innovation Solution
The proposed solution involves pre-amplifying the base-emitter voltage difference (ΔVBE) using switched-capacitor amplifier circuitry before ADC conversion, utilizing a common sensor reference voltage to avoid ADC headroom issues, and applying digital bandgap reference calibration during production to reduce runtime complexity and store correction values for curvature errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-amplification of ΔVBE is implemented using switched-capacitor amplifier circuitry, then temperature measurement precision is improved, but device complexity increases
Solution Approach 1:
A switched-capacitor amplifier circuit is introduced as an intermediary component between the temperature sensing element (BJT) and the ADC. This amplifier pre-amplifies the small ΔVBE signal before it reaches the ADC, enabling accurate temperature measurement with a low-resolution ADC. The amplifier acts as a mediator that bridges the gap between the微弱 signal and the ADC's input requirements, resolving the contradiction by improving measurement precision while keeping the ADC itself simple.
2Measurement precision
If high-resolution ADC is used to improve temperature measurement accuracy, then measurement precision is improved, but power consumption and die area increase
Solution Approach 1:
The switched-capacitor amplifier performs preliminary amplification of the ΔVBE signal before it enters the ADC. By pre-amplifying the signal to utilize the full dynamic range of a low-resolution ADC, the system achieves high measurement precision without requiring a high-resolution (and thus high-power) ADC. This preliminary action allows the use of a simpler, lower-power ADC while maintaining accurate temperature measurement.
3Measurement precision
If analog circuitry is added for curvature correction, then temperature measurement accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent replaces analog curvature correction circuitry with digital correction methods. The switched-capacitor amplifier and subsequent digital signal processing perform the curvature correction in the digital domain rather than requiring additional analog components. This substitution reduces device complexity and power consumption while maintaining or improving temperature measurement accuracy through digital algorithms that can be implemented in software or firmware.
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 allows for high-accuracy temperature sensing with a low-resolution ADC, reducing power consumption and die area while achieving 1 degree Celsius precision without additional analog circuitry, suitable for various electronic devices.
Implementation Method 1
Because of the known temperature and current dependence of the forward-biased base-emitter junction voltage (VBE) at the BJT device, the BJT device may be suitable for temperature measurement. For example, a temperature measurement may be obtained from the BJT device by subtracting two VBE voltages at two different bias currents having a known ratio. The difference between the two VBEs is proportional to absolute temperature (PTAT) of the BJT device.
Data Source
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AI summary
Systems, devices, and methods related to temperature sensors for electronic devices are provided. An example temperature sensor device includes analog temperature sensor circuitry to generate a plurality of voltages indicative of a temperature; an analog-to-digital converter (ADC) disposed downstream of the analog temperature sensing circuitry; switched-capacitor amplifier circuitry disposed before the ADC, the switched-capacitor amplifier circuitry comprising a single-ended amplifier to amplify the plurality of voltages with respect to a common voltage; a first switch coupled between the analog temperature sensor circuitry and the switched-capacitor amplifier circuitry to provide a sampling phase and an integration phase; and digital calculation circuitry to calculate a temperature value based on the plurality of amplified voltages.