Flash Memory Read Retry Optimization Using Temperature Compensation
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Solution Overview
Problem
Legacy Read Retry methods in flash memory storage devices are inefficient due to the need to test multiple sense voltages sequentially, leading to significant performance drops and increased test times, especially when temperature changes affect the error bit correction capabilities of ECC engines.
Innovation Solution
A method that utilizes current and programming temperature information to optimize the Read Retry process by calculating a starting test voltage based on temperature data, allowing for a more efficient sequence of voltage tests, thereby reducing unnecessary tests and improving performance across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Legacy Read Retry method tests different sense voltage one by one from minimum to maximum, then it can find suitable sense voltage to correct errors, but it takes significant time causing performance drop
Solution Approach 1:
The patent applies preliminary action by performing a test read operation before the actual read operation to determine the appropriate sense voltage. The controller reads test data stored in the memory cell array using different read voltages, determines which voltage successfully reads the test data, and sets the initial read voltage for the actual operation based on this preliminary test result. This eliminates the need to sequentially test multiple voltages during the actual read operation.
Solution Approach 2:
The patent changes the parameter of read voltage by dynamically adjusting the initial read voltage based on temperature information. The controller obtains temperature information, determines a corresponding read voltage range based on this temperature, and performs the test read operation within this optimized range. This parameter adaptation to temperature conditions reduces the number of voltage tests needed while maintaining reliable error correction.
2Productivity
If temperature information is used to optimize Read Retry sequence, then test time is reduced and performance is improved, but device complexity increases due to additional temperature sensing and calculation
Solution Approach 1:
The patent applies universality by using the existing thermal sensor, which was originally designed for other purposes (such as monitoring memory cell temperature during programming), for the additional function of optimizing read operations. The same temperature information serves multiple functions: monitoring cell temperature during write operations and determining optimal read voltage ranges during read operations. This multi-functionality avoids adding dedicated temperature sensing circuitry solely for read optimization.
3Reliability
If multiple test voltages are applied sequentially to ensure error correction, then reliability is maintained, but productivity decreases due to repeated testing
Solution Approach 1:
The patent performs a preliminary test read operation using test data before performing the actual read operation on user data. The controller determines the successful read voltage from this preliminary test and applies it as the initial voltage for the actual read operation. This preliminary action ensures data read accuracy while eliminating the need for sequential voltage testing during the actual read operation, thereby improving throughput.
Data Source
AI summary
A method of a flash memory storage device using Read Retry method is disclosed. This method includes using a thermal sensor to records temperature information while programming flash memory, and using this temperature information to compensate the temperature difference between program and read operation to improve Read Retry performance.