Nonvolatile Memory Soft-Bit Read with Temperature-Dependent Sense Time
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Solution Overview
Problem
Non-volatile memory read operations are affected by temperature variations, leading to inaccuracies in determining the data state of memory cells due to shifts in threshold voltage distributions.
Innovation Solution
Implementing a soft-read (soft-bit read or SBR) mechanism that uses temperature-dependent sense time offsets to provide probability information for hard-read data, adjusting sense times based on on-chip temperature measurements to compensate for temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature compensation is implemented using temperature-dependent sense time offsets, then reading accuracy is improved, but device complexity increases
Solution Approach 1:
The patent pre-calculates and stores sense time offset values for different temperature ranges in a lookup table during device fabrication or initialization. During read operations, the system simply queries the appropriate offset from the table based on measured temperature, avoiding complex real-time calculations and reducing operational complexity while maintaining high reading accuracy
Solution Approach 2:
The system dynamically adjusts the sense time parameter based on temperature conditions by selecting different offset values from the lookup table. This parameter adaptation allows the read operation to compensate for temperature-induced threshold voltage shifts without requiring complex control logic, thereby improving measurement precision while managing device complexity
2Reliability
If temperature measurement and compensation operations are added, then reliability is improved, but processing time increases
Solution Approach 1:
The system performs temperature measurements and sense time offset adjustments periodically or at predetermined intervals rather than continuously for every read operation. This approach maintains reliability by ensuring compensation is applied when necessary while minimizing the impact on processing time by avoiding redundant measurements and calculations
Solution Approach 2:
Temperature compensation parameters are pre-computed and stored in lookup tables during device initialization or fabrication. During actual read operations, the system only needs to perform a simple table lookup based on the current temperature measurement, significantly reducing the processing time required for compensation while maintaining high reliability
Data Source
AI summary
Control circuits configured to connect to a plurality of nonvolatile memory cells are configured to perform a soft-bit read of the plurality of nonvolatile memory cells by sensing the plurality of nonvolatile memory cells for a sense-time. The sense-time is obtained by adding a soft-read offset time to a hard-read sense time. The soft-read offset time is dependent on a temperature measurement value such that different soft-read offset times are applied for different temperature measurement values.