Memory Driver Calibration for Faster Linear PAM Signaling
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Solution Overview
Problem
Current memory devices face challenges in performing Zero-Quiescent Point (ZQ) calibration efficiently, particularly in ensuring linearity and speed, especially when dealing with multiple pull-up and pull-down circuits in pulse amplitude modulation (PAM) systems.
Innovation Solution
A method and memory device design that measure the linearity of multiple pull-up and pull-down circuits using initial codes to determine calibration settings, allowing for independent resistance value adjustments in each circuit, thereby optimizing the calibration method for faster and more linear signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If ZQ calibration is performed using shared codes for pull-up and pull-down circuits, then device complexity is reduced, but calibration speed and linearity are compromised
Solution Approach 1:
The patent divides the calibration process into two distinct phases: a first calibration phase that determines pull-down circuit codes, and a second calibration phase that determines pull-up circuit codes using the results from the first phase. This segmentation allows each phase to be optimized independently, improving overall calibration speed and linearity while maintaining manageable device complexity.
Solution Approach 2:
The patent performs preliminary calibration of the pull-down circuits in the first calibration phase, storing their codes in a lookup table. This preliminary action enables the second calibration phase to quickly determine pull-up codes by referencing the pre-calculated pull-down codes, significantly accelerating the overall calibration process while ensuring linearity.
2Measurement precision
If separate codes are used for each pull-up and pull-down circuit, then linearity is improved, but device complexity and calibration time increase
Solution Approach 1:
The patent merges the calibration results of pull-up and pull-down circuits by using the pull-down circuit codes (determined in the first phase) as a basis for determining the pull-up circuit codes (in the second phase). This merging approach ensures linearity through separate code determination while reducing complexity by reusing calibration data across both circuit types.
Solution Approach 2:
The patent changes the calibration parameters dynamically: in the first phase, it calibrates pull-down circuits with specific resistance values, and in the second phase, it uses those results to calibrate pull-up circuits with corresponding resistance values. This parameter change strategy ensures linearity while managing complexity through systematic parameter reuse.
3Measurement precision
If multiple calibration loops are executed for each circuit, then linearity is ensured, but calibration time increases
Solution Approach 1:
The patent executes preliminary calibration loops for pull-down circuits in the first phase and stores the results. This preliminary action eliminates the need to re-execute similar calibration loops for pull-up circuits, ensuring linearity through thorough initial calibration while significantly reducing the total calibration time by avoiding redundant iterations.
Solution Approach 2:
The patent implements feedback by using the calibration results from the first phase (pull-down circuit codes) as input for the second phase (pull-up circuit calibration). This feedback mechanism ensures linearity is maintained through iterative refinement while reducing total calibration time by leveraging previous calibration data rather than starting from scratch.
Data Source
AI summary
A method includes measuring a linearity of a first pull-up circuit, a second pull-up circuit, a third pull-up circuit, a first pull-down circuit, a second pull-down circuit and a third pull-down circuit using an initial pull-up code and an initial pull-down code, each of the first pull-up circuit, the second pull-up circuit and the third pull-up circuit having a respective resistance value determined based on a respective pull-up code, and each of the first pull-down circuit, the second pull-down circuit and the third pull-down circuit having a respective resistance value determined based on a respective pull-down code, and determining a calibration setting indicator based on the measurement result, the calibration setting indicator indicating a calibration method of a transmission driver including the first pull-up circuit, the second pull-up circuit, the third pull-up circuit, the first pull-down circuit, the second pull-down circuit and the third pull-down circuit.