Charge Trap Flash Memory Controller Adaptive Read Voltage
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Solution Overview
Problem
Charge trap flash (CTF) memory devices face read failures due to the fast charge loss phenomenon, which causes threshold voltage variations, leading to increased read latency and the need for adaptive read conditions based on program elapsed time.
Innovation Solution
A memory controller system that utilizes two tables - a program order table and a time stamp table - to manage the program order and elapsed time of memory areas, allowing for dynamic adjustment of read conditions such as read voltage based on the estimated elapsed time since programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fixed read conditions are used in CTF memory, then device complexity is low, but read failures occur due to fast charge loss phenomenon
Solution Approach 1:
The system performs preliminary actions by maintaining a program order table and timestamp table that record the programming sequence and elapsed time of each memory area. When a read request arrives, the controller queries these tables to determine the program elapsed time before executing the read operation, thereby proactively preparing the appropriate read conditions to prevent read failures caused by fast charge loss.
Solution Approach 2:
The system implements feedback mechanisms by continuously monitoring the program elapsed time through timestamp tables and using this information to dynamically adjust read conditions. The controller queries the program order table and timestamp table to obtain feedback about when each memory area was programmed, then uses this feedback to select optimal read voltages and conditions that compensate for charge loss over time.
2Reliability
If adaptive read conditions based on program elapsed time are implemented, then read failures are reduced, but device complexity increases due to additional tables and control logic
Solution Approach 1:
The control system is segmented into distinct functional components: a program order table that stores sequencing information, a timestamp table that stores elapsed time data, and a controller that queries these tables and adjusts read conditions. This segmentation allows each component to have a specific, simplified function while collectively providing sophisticated adaptive read control that reduces read failures.
3Reliability
If program order table and timestamp table are maintained, then read conditions can be optimized in real-time, but loss of time occurs due to additional query operations
Solution Approach 1:
The program order table and timestamp table are maintained in real-time as programming operations occur, performing preliminary actions that store necessary information before read requests arrive. This allows the controller to quickly query pre-computed data rather than performing complex calculations during read operations, minimizing additional latency while ensuring data integrity.
4Measurement precision
If read voltage is dynamically adjusted based on elapsed time, then threshold voltage variations are compensated, but ease of operation decreases due to complex read control
Solution Approach 1:
The system implements self-service by automatically querying the program order table and timestamp table to determine the appropriate read conditions without requiring external intervention. The controller autonomously adjusts read voltages based on the program elapsed time, compensating for threshold voltage variations and maintaining measurement precision while keeping the operation process transparent to the user.
Data Source
AI summary
One embodiment includes obtaining programming order information for the memory area from a first table based on address information. The programming order information indicates an order in which the memory area was programmed. The embodiment further includes determining an estimated elapsed time by accessing a second table based on the obtained programming order information. The estimated elapsed time indicating time that has elapsed since the portion of the memory area was last programmed. The embodiment includes controlling the memory based on the estimated elapsed time.