MOSFET Voltage Reference Compensation for Low-Voltage Accuracy
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Solution Overview
Problem
Existing voltage reference circuits, particularly in low-voltage applications, face challenges in maintaining accuracy and temperature independence due to limitations in bipolar junction transistor (BJT) technology, which is constrained by BJT or diode cut-in voltages, necessitating a high accuracy, low temperature coefficient (TC) solution using metal-oxide semiconductor (MOS) based technology.
Innovation Solution
The implementation of a voltage reference circuit that combines proportional-to-absolute-temperature (PTAT) and complementary-to-absolute-temperature (CTAT) circuits using metal-oxide-semiconductor field-effect transistors (MOSFETs) to generate a substantially temperature-independent voltage output, offsetting temperature-induced variations through a balanced PTAT and CTAT mechanism, with adjustable resistor and MOS trimming circuits for fine-tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If BJT-based temperature compensation circuits are used, then temperature compensation capability is improved, but device complexity and voltage headroom requirements increase due to BJT cut-in voltages
Solution Approach 1:
The patent substitutes BJT-based temperature compensation mechanisms with MOSFET-based compensation circuits. Specifically, it uses MOSFETs (M1, M2, M3, M4) to create PTAT and CTAT current sources that compensate for temperature effects on the bandgap reference voltage, thereby eliminating the need for BJT cut-in voltages and reducing circuit complexity while maintaining temperature compensation capability
Solution Approach 2:
The patent changes the operating parameters by using MOSFETs instead of BJTs, operating in the subthreshold region to achieve low-voltage operation. The compensation is achieved by adjusting the ratio of MOSFET sizes and resistor values to balance the PTAT and CTAT components, thereby achieving temperature independence without BJT cut-in voltage constraints
2Use of energy by moving object
If MOS-based voltage reference circuits are used, then voltage headroom is reduced, but temperature coefficient accuracy deteriorates due to lack of inherent temperature compensation
Solution Approach 1:
The patent segments the voltage reference circuit into distinct functional blocks: a bandgap core circuit (M1, M2, R1, R2) that generates a temperature-dependent reference voltage, and separate PTAT (M3, R3) and CTAT (M4, R4) compensation circuits. This segmentation allows independent optimization of each block and facilitates precise temperature compensation through controlled combination of the segments
Solution Approach 2:
The patent implements feedback mechanisms where the PTAT and CTAT compensation circuits continuously monitor temperature effects and adjust the output voltage accordingly. The compensation currents are fed back to the bandgap core to counteract temperature drift, achieving stable temperature coefficient accuracy while operating at low voltage headroom
3Use of energy by stationary object
If low-voltage operation is implemented, then power consumption is reduced, but temperature independence deteriorates due to constraints on compensation circuit design
Solution Approach 1:
The patent employs dynamic compensation by using MOSFETs operated in the subthreshold region, which exhibit exponential current-voltage characteristics that are highly sensitive to temperature. This dynamic behavior allows the compensation circuits to actively track and counteract temperature variations in real-time, maintaining temperature independence even at low supply voltages where static compensation would fail
Solution Approach 2:
The patent creates a composite circuit architecture that combines multiple MOSFET-based compensation mechanisms (PTAT and CTAT) with the bandgap reference core. This composite structure leverages the complementary temperature characteristics of different MOSFET configurations to achieve robust temperature independence that neither component could achieve alone, while maintaining low-voltage operation
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 results in a stable, temperature-independent voltage reference that is insensitive to temperature and power supply changes, enhancing the accuracy and reliability of low-voltage applications, particularly in IoT devices with low power consumption.
Implementation Method 1
The PTAT circuit is configured to produce an increase in magnitude of a reference voltage with an increase of temperature
Implementation Method 2
The CTAT circuit is configured to produce a decrease in magnitude of the reference voltage with an increase of temperature
Data Source
AI summary
Systems and methods are provided for generating a temperature compensated reference voltage. A temperature compensation circuit may include a proportional-to-absolute temperature (PTAT) circuit, and a complementary-to-absolute temperature (CTAT) circuit, with the PTAT circuit and the CTAT circuit including at least one common metal-oxide-semiconductor field-effect transistor (MOSFET) and being configured to collectively generate a reference voltage in response to a regulated current input. The PTAT circuit may be configured to produce an increase in magnitude of the reference voltage with an increase of temperature, and the CTAT circuit may be configured to generated a decrease in magnitude of the reference voltage with the increase of temperature, wherein the increase in magnitude of the reference voltage produced by the PTAT circuit is at least partially offset by the decrease in magnitude of the reference voltage produced by the CTAT circuit.