Comparator Offset Correction Using Charge-Sharing Calibration
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Solution Overview
Problem
Mismatch between components in comparators, such as input transistors, reduces the accuracy of comparison results, particularly in high-speed and miniaturized semiconductor devices, necessitating an effective offset correction mechanism.
Innovation Solution
A comparator with controllable offset-correction components, including holding capacitors and switching circuitry, adjusts offset-correction signals through charge sharing and controlled voltage supplies to achieve high-speed and low-offset performance, enabling accurate comparison.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If component size is reduced for miniaturization, then device area is reduced, but manufacturing precision deteriorates due to increased component mismatch
Solution Approach 1:
The comparator performs self-calibration by automatically detecting and correcting its own offset errors through the calibration circuitry. The system uses the comparator's own output to control the calibration process, eliminating the need for external calibration equipment and achieving self-correction of manufacturing imperfections.
Solution Approach 2:
The calibration circuitry dynamically adjusts electrical parameters (voltage levels, current values) to compensate for component mismatch. By changing these parameters during calibration mode, the system corrects offset errors caused by manufacturing variations without requiring physical component replacement.
2Measurement precision
If offset correction circuitry is added to improve measurement precision, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The calibration circuitry is integrated with the main comparator circuit, sharing common transistors, capacitors, and interconnect structures. The first and second calibration circuits are merged with the differential pair and latch circuitry, reducing the need for separate discrete components and minimizing additional area overhead.
Solution Approach 2:
The same comparator hardware performs both normal comparison operations and self-calibration functions. The calibration circuits utilize existing comparator components (transistors, capacitors, interconnects) for multiple purposes: signal comparison during normal operation and offset correction during calibration mode, eliminating the need for dedicated calibration-only hardware.
3Measurement precision
If calibration is performed frequently to maintain measurement precision, then manufacturing precision is maintained, but productivity decreases
Solution Approach 1:
The comparator uses feedback from its own output signals to control the calibration process. The calibration circuits are activated based on detected offset conditions, and the calibration continues until the offset is minimized, creating a self-regulating system that performs calibration only when necessary rather than continuously.
Solution Approach 2:
The self-calibration process operates periodically or on-demand based on system requirements, rather than continuously. The calibration circuits can be activated at specific intervals or triggered by detected performance degradation, allowing normal high-speed operation to continue between calibration events and maximizing productivity.
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-resolution comparator with low current consumption, allowing for rapid and precise offset compensation, maintaining accuracy and reducing the frequency of calibration needs.
Implementation Method 1
the at least one offset-correction circuit comprises a holding capacitor, a supply capacitor and switching circuitry, the holding capacitor connected to the input terminal of the offset-correction component concerned and configured to provide the offset-correction signal at the input terminal concerned based on charge stored on that holding capacitor
Implementation Method 2
the switching circuitry is configured, in a charging operation, to connect the supply capacitor to a charging-operation voltage supply to store charge on that capacitor, and, in a charge-sharing operation, to disconnect the supply capacitor from the charging-operation voltage supply and connect it to the holding capacitor to adjust the charge stored on the holding capacitor (through charge sharing between the supply and holding capacitors)
Data Source
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AI summary
A comparator (100) comprising: first and second input transistors (42, 44) connected to control signals at first and second nodes (47, 49) of the comparator based on first and second input signals (INP, INM), respectively; latch circuitry (45); at least one controllable offset-correction component (66, 76) having an input terminal and connected to control the signal at one of the first and second nodes based on an offset-correction signal (VCALP, VCALM) provided at its input terminal; for each controllable offset-correction component, an offset correction circuit (60, 70) configured to provide the offset-correction signal provided at its input terminal; and control circuitry (55). The at least one offset-correction circuit comprises a holding capacitor (64, 74), a supply capacitor (62, 72) and switching circuitry (61, 63, 65, 71, 73, 75). For the at least one offset-correction circuit, the switching circuitry is configured, in a charging operation, to connect the supply capacitor to a charging-operation voltage supply to store charge on that capacitor, and, in a charge-sharing operation, to disconnect the supply capacitor from the charging-operation voltage supply and connect it to the holding capacitor. The control circuitry (55) is configured, based on a control signal (C), to control the at least one offset-correction circuit to: control an amount by which the offset-correction signal is adjusted; and/or in a bypass operation, connect the input terminal of the at least one controllable offset-correction component to a bypass-operation reference voltage supply; and/or in a maintenance operation, control the charging-operation voltage supply and/or the bypass-operation voltage supply to control leakage of the charge stored on the holding capacitor.