Reference Voltage Calibration Circuit for High-Order Temperature Compensation
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Solution Overview
Problem
Existing reference voltage calibration methods are limited in universality, particularly for reference voltage sources without resistors, such as buried Zener and sub-threshold CMOS bandgap sources, and struggle with high-order temperature compensation, leading to component mismatch and offset issues in analog integrated circuits.
Innovation Solution
A reference voltage temperature coefficient calibration circuit utilizing an operational amplifier with an adjustable current module, which generates an adjusting current related to the bias current source and Kelvin temperature, allowing for calibration of first-order to high-order temperature coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional adjusting methods are used to adjust resistance or current in the reference voltage source circuit, then the first-order temperature coefficient can be adjusted, but the method lacks universality and cannot be applied to reference voltage sources without resistors such as buried Zener and sub-threshold CMOS bandgap sources
Solution Approach 1:
The patent introduces a universal calibration circuit that can adjust temperature coefficients for multiple types of reference voltage sources (buried Zener, XFET, bandgap, etc.) using the same adjustment mechanism. The calibration circuit uses operational amplifiers and adjustable resistors that work across different reference voltage source architectures, eliminating the need for structure-specific adjustment methods.
Solution Approach 2:
The patent introduces an intermediate calibration circuit as a mediator between the reference voltage source and the output. This calibration circuit includes operational amplifiers and adjustable components that can compensate for temperature coefficients without requiring modifications to the original reference voltage source structure, enabling universal applicability.
2Measurement precision
If high-order temperature compensation circuits are configured to achieve precision above 12 bits, then higher precision can be obtained, but component mismatch is induced causing offset of the reference voltage
Solution Approach 1:
The patent implements a staged calibration approach where first-order and second-order temperature coefficients are adjusted separately through different adjustment mechanisms. This partial action approach allows achieving high precision (above 12 bits) without requiring a single complex high-order compensation circuit that would induce significant component mismatch and offset.
Solution Approach 2:
The patent segments the temperature compensation into multiple independent adjustment stages - first-order temperature coefficient adjustment and second-order temperature coefficient adjustment. Each stage uses separate adjustment components, which reduces the cumulative mismatch error compared to a single high-order compensation circuit while achieving the same or better precision.
3Ease of operation
If adjustment of reference voltage is implemented in sub-threshold CMOS bandgap reference voltage source, then calibration can be performed, but the small current and component size make adjustment difficult
Solution Approach 1:
The patent uses operational amplifiers with high gain to amplify the effect of small adjustment currents. The calibration circuit copies and amplifies the adjustment signal, allowing precise adjustment of the reference voltage even with the small currents present in sub-threshold CMOS bandgap reference voltage sources. This enables ease of operation without requiring large adjustment currents that would be incompatible with the small component sizes.
Data Source
AI summary
The present invention relates to a reference voltage temperature coefficient calibration circuit. The circuit comprises: an operational amplifier comprising an input pair transistor, a load pair transistor, and a bias current source, an inverted input terminal of the operational amplifier being connected to an output terminal of the operational amplifier; and an adjustable current module connected in parallel to the load pair transistor, the adjustable current module being configured to generate an adjusting current, the adjusting current being used to adjust an offset current flowing through the input pair transistor, wherein the adjusting current is related to a current of the bias current source and an order of Kelvin temperature. The present invention is applicable to calibration of first-order to high-order temperature coefficients of a reference voltage in a circuit, and has universality.