Comparator Offset Calibration Circuit for Temperature Drift in ADCs
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Solution Overview
Problem
Existing analog-to-digital converters (ADCs) face challenges in compensating for offset drift due to temperature changes and other factors, leading to performance issues that traditional trimming methods cannot fully address.
Innovation Solution
Implementing a comparator circuit with an offset control and calibration circuit, including a charge pump to manage net charge during pull-up and pull-down phases, and a leakage cancellation circuit to simulate and correct digital-to-analog converter errors, ensuring finer offset calibration and reduced on-die area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional trimming methods are used to correct offset, then initial offset can be compensated, but offset drift due to temperature change cannot be fully corrected
Solution Approach 1:
The offset calibration circuit performs preliminary offset calibration by controlling the net charge of the offset signal during pull-up and pull-down phases before the ADC operates. This preliminary action ensures that offset drift due to temperature changes is compensated in advance, improving both measurement precision and temperature stability.
Solution Approach 2:
The system uses feedback mechanisms where the offset calibration circuit continuously monitors and adjusts the offset signal based on temperature variations and operational conditions. The charge pump responds to calibration control signals to maintain proper offset levels, creating a closed-loop system that adapts to temperature drift.
2Measurement precision
If offset calibration circuitry is added to improve offset correction, then measurement precision improves, but device complexity increases
Solution Approach 1:
The offset calibration circuit is merged with the existing comparator and charge pump structures. The calibration control signals are integrated into the existing control logic, and the same charge pump hardware is used for both normal operation and offset calibration, reducing the need for separate dedicated calibration hardware.
Solution Approach 2:
The charge pump serves multiple functions: it operates during normal ADC conversion cycles and also performs offset calibration when control signals indicate calibration mode. The comparator circuitry is used for both signal comparison and offset detection, eliminating the need for separate calibration-specific components.
3Measurement precision
If finer offset calibration is implemented, then measurement precision improves, but die area increases
Solution Approach 1:
The system uses dynamic control of the charge pump during calibration phases to achieve fine offset adjustment. By controlling the timing and duration of pull-up and pull-down phases dynamically, the system can make precise offset corrections without requiring large calibration capacitors or multiple calibration steps, thus saving die area.
Solution Approach 2:
The offset calibration is achieved by changing the net charge parameter of the offset signal through controlled charging and discharging cycles. By adjusting the charge pump current and timing parameters, fine offset calibration is achieved without increasing the physical size of calibration components.
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
Achieves improved performance and reduced die area in ADCs by enabling finer offset calibration and correcting leakage errors, suitable for applications like multi-phase DC to DC power converters.
Implementation Method 1
The offset calibration circuit includes a charge pump and is configured to provide the offset signal responsive to the calibration control signals, in which the calibration control signals are provided to control a net charge of the offset signal during pull-up and pull-down phases of the charge pump
Implementation Method 2
A capacitor can be coupled to the input of the comparator circuit
Data Source
AI summary
In a described example, a circuit includes a comparator circuit including an input, a first output, and a second output. An offset control circuit includes a first input, a second input, a first output, and a second output, in which the first input is coupled to the first output of the comparator circuit, the second input is coupled to the second output of the comparator circuit. A first delay circuit is coupled between the first input and the first output of the offset control circuit. A second delay circuit is coupled between the second input and the second output of the offset control circuit. An offset calibration circuit has a first input and a second input, in which the first input is coupled to the first output of the offset control circuit, the second input is coupled to the second output of the offset control circuit.