Pseudo Clock System for SSD Data Retention Estimation
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Solution Overview
Problem
Solid state drives (SSDs) face inefficiencies in data retention time estimation due to the lack of an internal real-time clock, leading to suboptimal read operations and increased ECC failures, especially with temperature variations.
Innovation Solution
A pseudo clock system is implemented to estimate effective retention time for NAND memory devices, accounting for temperature deviations and storing optimal read trims in a 4-dimensional table, allowing for adjusted read operations to minimize ECC failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pseudo clock system is implemented to estimate effective retention time, then data integrity is improved and ECC failures are reduced, but device complexity increases
Solution Approach 1:
The patent introduces a pseudo clock system as an intermediary component that estimates effective retention time without requiring a full real-time clock. This mediator provides the necessary time estimation functionality while avoiding the complexity of implementing complete clock infrastructure in the SSD, thus improving data integrity while limiting the increase in device complexity.
Solution Approach 2:
The pseudo clock system performs self-service by estimating retention time based on internal observations and measurements rather than relying on external real-time clock infrastructure. The system uses observed data patterns and retention characteristics to autonomously determine effective retention time, reducing dependency on complex external timing mechanisms.
2Measurement precision
If temperature-adjusted read trims are applied to minimize ECC failures, then read operation accuracy is improved, but processing overhead increases
Solution Approach 1:
The patent applies local quality by using temperature-adjusted read trims specifically for read operations where they are most needed, rather than uniformly applying complex processing to all operations. The read trim adjustments are localized to the read path and are based on local temperature conditions and retention time estimates, improving read accuracy while avoiding unnecessary processing overhead in other system areas.
Solution Approach 2:
The system dynamically changes read trim parameters based on temperature conditions and estimated retention time. By adjusting these parameters adaptively rather than using fixed values, the system improves read operation accuracy under varying conditions while the changes are computed efficiently using pre-characterized data to minimize processing overhead.
3Productivity
If efficient retention time estimation is implemented, then productivity is improved by reducing read retry frequency, but device complexity increases due to pseudo clock system
Solution Approach 1:
The pseudo clock system performs preliminary action by estimating effective retention time in advance of read operations. This allows the system to proactively adjust read trims and prepare optimal read parameters before actual read operations occur, reducing the need for read retries and improving overall productivity. The retention time estimation is performed ahead of time based on write timing and temperature conditions.
Data Source
AI summary
A system for controlling a solid state drive is disclosed that includes a plurality of NAND memory devices, each NAND memory device further comprising at least one die, a plurality of blocks associated with each of the dies, and a plurality of pages associated with each of the blocks. A pseudo clock system configured to determine a pseudo clock value for each of the NAND memory devices. An effective retention time system coupled to the plurality of NAND memory devices and configured to determine a maximum effective retention time for each of the NAND memory devices as a function of the pseudo clock value for the NAND memory device.