Code Shift Circuit for ZQ Driving Strength Compensation
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Solution Overview
Problem
The existing ZQ calibration methods struggle to accurately adjust the output impedance of semiconductor memory devices to account for changes in temperature and voltage, leading to signal distortion and potential setup/hold failures due to impedance mismatch, especially when increasing resolution within the constraints of a short ZQ calibration command period.
Innovation Solution
A code shift calculation circuit and method that generates a shift value to adjust the driving strength code calibrated by ZQ calibration, using first and second operation circuits to calculate output values based on temperature and voltage differences, respectively, and summing these values to adjust the driving strength code, thereby eliminating deviations caused by temperature and voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the code width that can be moved by ZQCS command is increased to improve resistance accuracy, then the resolution of output driver is improved, but the signal transmission may not conform to specification due to short ZQCS command period
Solution Approach 1:
The patent performs preliminary ZQ calibration to obtain initial code values before the actual ZQCS command execution. By pre-calculating and storing code values that will be needed, the system can quickly apply corrections without extending the ZQCS command period, thus maintaining signal transmission compliance while achieving high resolution through pre-computed accurate code values.
Solution Approach 2:
The patent divides the code adjustment process into multiple segments: initial ZQ calibration to obtain baseline code, then separate temperature and voltage compensation calculations that are applied independently. This segmentation allows the system to achieve high overall precision through multiple smaller adjustments rather than requiring a single large code movement that would violate timing constraints.
2Reliability
If the code width is not increased to maintain signal transmission compliance, then the ZQCS command period constraint is satisfied, but the change in output impedance caused by temperature change or voltage change cannot be eliminated
Solution Approach 1:
The patent changes the parameters used for compensation by separately calculating temperature compensation codes and voltage compensation codes, then combining them. This approach allows the system to achieve accurate output impedance adjustment through parameter decomposition and recombination, maintaining signal compliance while eliminating impedance changes caused by temperature and voltage variations.
Solution Approach 2:
The patent introduces intermediary compensation codes for temperature and voltage that mediate between the fixed ZQCS command period constraint and the need for accurate output impedance adjustment. These intermediary codes are calculated separately and combined to achieve the final accurate code value without requiring extended calibration time.
3Measurement precision
If multiple calibration operations are performed to eliminate temperature and voltage effects, then the output impedance accuracy is improved, but the calibration time increases
Solution Approach 1:
The patent performs preliminary temperature and voltage compensation calculations during idle periods or in parallel with other operations, so that when actual calibration is needed, the compensation codes are already computed and ready for immediate application. This eliminates the need for sequential calibration operations, maintaining high accuracy without increasing total calibration time.
Solution Approach 2:
The patent maintains continuous tracking of temperature and voltage parameters, continuously updating compensation codes as conditions change. This continuous action allows the system to maintain accurate output impedance without requiring repeated discrete calibration operations, thereby improving precision while minimizing calibration time overhead.
Data Source
AI summary
A code shift calculation circuit is provided. A first operation circuit of the code shift calculation circuit generates a first output value according to a temperature difference and a first change rate of a driving strength code to temperature. The temperature difference is a difference between a previous temperature when getting a previous ZQ command and a current temperature when getting a current ZQ command. A second operation circuit generates a second output value according to a voltage difference and a second change rate of the driving strength code to voltage. The voltage difference is a difference between a previous working voltage when getting the previous ZQ command and a current working voltage when getting the current ZQ command. A third operation circuit sums up the first output value and the second output value to generate a shift value, thereby adjusting the driving strength code calibrated by ZQ calibration.