Refresh Control Circuit Digital Conversion Stability
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Solution Overview
Problem
Existing refresh control circuits in semiconductor memory apparatuses face malfunctions due to errors in components like comparators and DA converters, leading to instability in controlling the refresh signal period according to temperature changes.
Innovation Solution
A refresh control circuit with a digital converting unit that generates comparison voltages and digital codes without a feedback structure, using control signals to adjust comparison voltages and prevent error amplification, ensuring stable refresh signal period control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback structure is used in the digital converting unit to improve measurement precision, then the temperature detection accuracy is improved, but component errors are amplified leading to system malfunction
Solution Approach 1:
The patent removes the feedback structure from the digital converting unit, extracting the problematic feedback loop that amplified component errors. The temperature detection is performed using open-loop comparators that convert the temperature detecting voltage to digital codes without feeding the output back to the input, thereby eliminating error amplification while maintaining detection functionality.
Solution Approach 2:
The patent performs preliminary calibration by storing correction values in lookup tables that compensate for component variations. The digital converting unit uses pre-calibrated comparison voltages and correction data to compensate for manufacturing tolerances and temperature drift, achieving accurate temperature detection without requiring feedback for error correction.
2Productivity
If the refresh signal period is controlled according to temperature changes, then the refresh operation efficiency is improved, but the control stability deteriorates due to component errors
Solution Approach 1:
The patent extracts and removes the feedback mechanism from the temperature-to-period conversion chain, using open-loop digital converting units that directly convert temperature detecting voltage to refresh period control signals without feedback. This eliminates the error amplification that would otherwise destabilize the refresh control.
Solution Approach 2:
The patent uses multiple simple comparators with fixed reference voltages instead of a single complex feedback-based converter. Each comparator performs a simple voltage comparison to generate one bit of the digital code, using inexpensive, low-precision components in parallel rather than expensive, high-precision feedback-based conversion.
3Area of stationary object
If high integration is used to reduce device size, then the device area is reduced, but manufacturing precision requirements increase leading to more defects
Solution Approach 1:
The patent segments the temperature-to-period conversion function into multiple independent comparator units, each handling one bit of the digital code. This segmentation allows each comparator to be simple and robust, tolerating manufacturing variations better than a single complex feedback converter would.
Solution Approach 2:
The patent changes the operating parameters of the comparators by using different reference voltages for each comparator in the chain. This allows the system to cover the full temperature range using multiple coarse steps rather than requiring a single high-precision converter, making the system more tolerant of manufacturing variations.
Data Source
AI summary
A refresh control circuit includes a temperature detecting unit that detects the temperature and generates a temperature detecting voltage, a control unit that generates a plurality of control signals, a digital converting unit that converts the temperature detecting voltage into a plurality of bits of digital code and outputs a plurality of bits of digital code according to the control of a plurality of control signals, and a refresh signal generating unit that generates a refresh signal with a period corresponding to the input of a plurality of bits of digital code.