Process-Independent Curvature Compensation for Bandgap Reference
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Solution Overview
Problem
Existing bandgap reference circuits suffer from temperature drift due to non-linear base-emitter voltage variations, which are difficult to compensate, especially in CMOS applications, leading to process-dependent and inaccurate reference voltages.
Innovation Solution
A voltage reference circuit with a process-independent curvature compensation scheme using a compensation controller and current subtraction to generate a temperature-compensated bandgap reference voltage, incorporating a hybrid topology with current and voltage signals to enhance regulation capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional bandgap reference circuits are used, then temperature compensation is achieved through base-emitter voltage and thermal voltage summation, but second-order temperature drift terms (T ln(T)) remain uncompensated, limiting temperature drift performance
Solution Approach 1:
The patent introduces a curvature compensation circuit as an intermediary component that generates a compensation current proportional to the second-order temperature drift term. This compensation current is subtracted from the main reference current to cancel out the unwanted T ln(T) term in the reference voltage, thereby improving temperature drift performance without affecting the first-order temperature compensation mechanism
Solution Approach 2:
The patent modifies the reference current parameter by adding a compensation current component that is specifically designed to counteract the second-order temperature dependence. The compensation current is generated using a combination of PTAT current and temperature-dependent transistor characteristics, changing the overall current parameter to achieve better temperature stability
2Measurement precision
If prior art curvature compensation methods are used, then temperature curvature is compensated, but the methods are process-dependent and cannot be effectively utilized with CMOS applications due to parasitic vertical bipolar transistor limitations
Solution Approach 1:
The patent designs a curvature compensation circuit that uses standard CMOS-compatible components and topologies, including PMOS transistors configured as current sources and resistors with temperature coefficients. The circuit achieves curvature compensation functionality while being fully compatible with standard CMOS fabrication processes, eliminating the need for special bipolar transistor structures
Solution Approach 2:
The patent replaces the mechanical/physical constraint of requiring parasitic vertical bipolar transistors with an electrical solution using CMOS transistors in specific configurations. By using PMOS transistors with controlled gate voltages and temperature-dependent characteristics, the circuit achieves the same curvature compensation effect without relying on bipolar transistor physics
3Use of energy by moving object
If low voltage operation is implemented to improve battery efficiency, then power consumption is reduced, but dynamic range decreases, demanding more accurate reference voltages
Solution Approach 1:
The patent changes the temperature dependence parameters of the reference voltage by introducing compensation currents that counteract second-order drift terms. This allows the reference circuit to maintain high accuracy even at low voltages where dynamic range is limited, as the compensation mechanism works effectively in the low-voltage regime
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 a high-precision, trim-free bandgap circuit with improved temperature stability, reducing temperature drift and making the circuit applicable to standard CMOS processes while simplifying layout and process matching.
Implementation Method 1
the compensation controller converting a node voltage of the second node into a second current
Implementation Method 2
a second transistor having a first terminal coupled to the power supply, a second terminal for mirroring the reference current from the bandgap reference circuit to provide a first current
Implementation Method 3
these bandgap reference circuits rely on certain temperature-dependent characteristics of the base-emitter voltage Vbe of a BJT transistor. Typically, these bandgap reference circuits operate on the principle of compensating the negative temperature coefficient of a bipolar transistor's base-emitter voltage with the positive temperature coefficient of the thermal voltage
Data Source
AI summary
In a voltage reference circuit, a bandgap reference circuit, for generating a bandgap reference voltage and a reference current, includes an operation amplifier, and a first transistor for providing the reference current. Another transistor mirrors the reference current to provide a first current. A compensation controller converts a node voltage from the bandgap reference circuit into a second current and performs current subtraction on the first current and the second current to provide a compensation feedback current to another node of the bandgap reference circuit. So that, second order temperature compensation is performed on the bandgap reference voltage.