ZQ Impedance Calibration with Dynamic Step Adjustment
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Solution Overview
Problem
The ZQ calibration process in semiconductor devices loses accuracy due to inconsistent voltage conditions, particularly when supply voltage includes DC ripple or variation, which can distort calibration and make it difficult to maintain consistent impedance across process, voltage, and temperature changes.
Innovation Solution
A dynamic adder/subtractor circuit is used in the ZQ calibration circuit to dynamically adjust step sizes based on the current ZQCODE value, allowing for more efficient impedance calibration by reducing calibration time and compensating for non-linear impedance curves, and a partial binary search or conversion circuitry is employed to reduce the number of calibration comparisons and improve noise immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ZQ calibration process is used, then impedance calibration can be performed, but calibration accuracy deteriorates due to inconsistent voltage conditions and DC ripple
Solution Approach 1:
The patent applies preliminary action by performing multiple calibration measurements before selecting the final calibration value. The system conducts a plurality of calibration measurements and selects a calibration value based on these preliminary results, which improves accuracy by avoiding the impact of transient voltage variations during any single measurement.
Solution Approach 2:
The patent implements periodic action by performing calibration measurements at multiple different times rather than a single continuous measurement. This periodic sampling approach allows the system to capture voltage variations and select the most accurate calibration value, effectively handling DC ripple and voltage inconsistencies.
2Productivity
If calibration time is reduced for efficiency, then productivity improves, but calibration accuracy deteriorates
Solution Approach 1:
The patent applies partial action by performing a limited number of calibration measurements (e.g., 2-4 measurements) rather than exhaustive continuous calibration. This partial sampling approach achieves sufficient accuracy for practical purposes while significantly reducing calibration time and improving productivity.
Solution Approach 2:
The system performs self-service by automatically selecting the most accurate calibration value from multiple measurements without requiring external intervention. The calibration circuit autonomously conducts multiple measurements, compares results, and selects the optimal calibration value, improving both accuracy and efficiency.
3Measurement precision
If voltage sampling period is extended to average out ripple, then measurement accuracy improves, but calibration time increases beyond practical limits
Solution Approach 1:
The patent performs preliminary voltage sampling and calibration measurements at multiple discrete time points before finalizing the calibration. By conducting measurements beforehand at different moments and selecting the best result, the system achieves accurate voltage measurement without requiring extended continuous sampling periods.
Solution Approach 2:
The system uses periodic action by sampling voltage at multiple distinct time points during the calibration process rather than continuous monitoring. This periodic sampling approach captures voltage variations effectively while maintaining practical calibration timing, avoiding the need for excessively long measurement periods.
Data Source
AI summary
Systems and methods for performing an efficient ZQ calibration are provided herein. The described techniques use non-linearity compensation circuitry configured to compensate for a non-linear relationship between variation in a plurality of ZQ calibration codes and corresponding resistance variations, by adjusting either: a magnitude of the adjustment to the calibration step, the ZQCODE to an alternative ZQCODE, or both the magnitude of the adjustment to the calibration step and the ZQCODE to the alternative ZQCODE.