ZQ Calibration Control Using Stored Codes for DRAM Impedance
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Solution Overview
Problem
Semiconductor memory devices, such as DRAM, face performance issues due to varying power supply voltages and temperatures, which affect impedance and require frequent impedance calibration, consuming higher power and potentially degrading performance.
Innovation Solution
A ZQ calibration control circuit that periodically compares current voltage and temperature conditions with pre-stored values, skipping calibration when conditions match and performing it otherwise, and updates a register array based on usage frequency to optimize impedance adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ZQ calibration is performed periodically to compensate for impedance variations, then impedance accuracy is improved, but power consumption increases and performance deteriorates
Solution Approach 1:
The patent stores calibration codes and their associated voltage/temperature conditions in advance in a register array. When the current conditions match a stored condition, the pre-stored calibration code is retrieved and applied without performing a new calibration, thus avoiding unnecessary power consumption while maintaining impedance accuracy.
Solution Approach 2:
The patent implements a feedback mechanism that monitors current voltage and temperature conditions, compares them with stored conditions, and selectively triggers calibration only when conditions change beyond a threshold. This feedback-based selective calibration reduces power consumption by avoiding redundant calibrations while maintaining impedance accuracy when needed.
2Measurement precision
If ZQ calibration is performed frequently to maintain impedance accuracy, then impedance accuracy is improved, but device performance deteriorates
Solution Approach 1:
The patent pre-stores multiple calibration codes corresponding to different voltage and temperature conditions in a register array. When current conditions match a stored condition, the corresponding pre-calibrated code is immediately applied without triggering a new calibration sequence, thus maintaining impedance accuracy while avoiding performance degradation from frequent calibration operations.
Solution Approach 2:
The patent implements periodic calibration only when voltage or temperature conditions change beyond predetermined thresholds, rather than performing continuous or overly frequent calibrations. This threshold-based periodic action maintains impedance accuracy while minimizing disruption to device performance by calibrating only when necessary.
3Reliability
If impedance calibration is performed to compensate for voltage and temperature variations, then reliability is improved, but power consumption increases
Solution Approach 1:
The patent stores calibration results and associated environmental conditions in advance in a register array. When current voltage and temperature conditions match stored conditions, the system retrieves and applies the pre-stored calibration code without performing energy-intensive calibration measurements, thus maintaining reliability while reducing power loss.
Solution Approach 2:
The patent uses feedback from voltage and temperature sensors to determine whether calibration is needed by comparing current conditions with stored conditions. Calibration is performed only when conditions change beyond a threshold, ensuring reliability through appropriate calibration while minimizing unnecessary energy loss from redundant calibration operations.
Data Source
AI summary
In an example semiconductor device, the voltage/temperature conditions of the semiconductor device and associated calibration codes of multiple instances of ZQ calibrations are pre-stored in a register array. When a pre-stored voltage/temperature condition occurs again, ZQ calibration is not performed. Instead, the associated pre-stored calibration code is retrieved from the register array and provided to the IO circuit. When a voltage/temperature condition of the semiconductor device does not match any pre-stored voltage/temperature condition in the register array, a ZQ calibration is performed. When the ZQ calibration is performed, a register in the register array is selected according to an update policy and updated by the calibration code newly provided by the ZQ calibration along with the voltage/temperature condition at the time when the ZQ calibration is performed.