Impedance Calibration Averaging for Ripple-Resistant Termination Codes
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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 is not effectively averaged within a single calibration event.
Innovation Solution
Performing multiple impedance calibrations over a period and averaging them to generate a subsequent calibration that reduces calibration error caused by DC ripple in the supply voltage, using a system with a controller and semiconductor devices that include a code generator and relay circuit to adjust output impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single impedance calibration is performed, then the calibration process is fast and simple, but the calibration accuracy is reduced due to DC ripple in supply voltage
Solution Approach 1:
The patent implements periodic impedance calibrations where multiple calibration measurements are performed at different time points within a calibration period. The supply voltage ripple has a specific frequency, and by performing multiple calibrations periodically, the system captures voltage variations and averages them out, thereby improving calibration accuracy while managing the time trade-off through structured periodic measurement cycles.
Solution Approach 2:
The patent combines multiple individual calibration measurements into a single averaged calibration result. By performing multiple calibrations and merging their results through averaging, the system reduces the impact of DC ripple on any single measurement, thereby improving overall calibration accuracy while the merged result is applied once to achieve the desired impedance matching.
2Measurement precision
If multiple impedance calibrations are performed and averaged, then calibration accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent segments the calibration process into distinct phases: performing multiple individual calibrations at different time points, averaging the results, and applying the final averaged calibration. This segmentation allows the system to manage complexity by breaking down the multi-calibration process into manageable steps that can be executed sequentially with controlled resource usage.
Solution Approach 2:
The patent performs multiple calibration measurements but only retains and applies the averaged result, effectively discarding the individual intermediate calibration values after they contribute to the average. This approach reduces the need to store and manage multiple calibration states simultaneously, thereby limiting the increase in device complexity while still benefiting from multiple measurements.
3Measurement precision
If the calibration period is extended to average out DC ripple, then calibration accuracy is improved, but the productivity decreases
Solution Approach 1:
The patent performs a specific number of calibrations within a calibration period that is sufficient to average out the DC ripple but not excessively long. By determining an optimal number of calibrations (e.g., enough to cover at least one full ripple cycle), the system achieves the necessary accuracy improvement without extending the calibration period unnecessarily, thereby balancing accuracy gains with productivity constraints.
Data Source
AI summary
A semiconductor device also includes programmable termination components and a calibration circuit. The calibration circuit generates impedance calibration codes. The calibration circuit also calibrates impedance of the programmable termination components based on an average impedance calibration code of the impedance calibration codes. The semiconductor device further includes an averaging circuit that determines the average impedance calibration code of the impedance calibration codes.