Adaptive Wordline Start Voltage via Sampling
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Solution Overview
Problem
Conventional memory systems face challenges in optimizing wordline start voltage, leading to inefficiencies in programming time and wear on memory devices, particularly due to voltage overshoot in memory devices with large wordline start voltage variations.
Innovation Solution
The implementation of adaptive wordline start voltage using wordline sampling and a maximum start voltage delta, where only a select number of wordlines are sampled to determine a wordline start voltage for the entirety of a memory block, thereby reducing programming time while preventing voltage overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all wordlines are sampled to determine accurate start voltage, then voltage overshoot is prevented, but programming time increases significantly
Solution Approach 1:
The memory block is divided into multiple decks, and only a selected subset of wordlines from each deck is sampled to determine the maximum start voltage delta. This segmentation approach reduces the total number of samples needed while still capturing the voltage variations across the memory block, thus preventing voltage overshoot without requiring all wordlines to be sampled.
Solution Approach 2:
Instead of sampling all wordlines (excessive action), the method samples only a sufficient subset of wordlines (partial action) to accurately determine the maximum start voltage delta. This partial sampling provides the necessary information to prevent voltage overshoot while significantly reducing the time cost compared to complete sampling.
2Measurement precision
If wordline sampling is performed for every programming operation, then accurate start voltage is maintained, but programming speed decreases
Solution Approach 1:
The maximum start voltage delta is determined in advance during a preliminary sampling phase, and then this pre-determined value is reused for subsequent programming operations. This preliminary action eliminates the need to perform complete wordline sampling for every programming operation, thereby maintaining voltage accuracy while significantly improving programming speed.
Solution Approach 2:
The method creates a representative sample of wordline characteristics by sampling only a subset of wordlines. This sampled information serves as a copy or proxy for the entire memory block's voltage characteristics, allowing accurate start voltage determination without examining every single wordline.
3Adaptability or versatility
If maximum start voltage delta is determined for each deck, then voltage variations are accounted for, but device complexity increases
Solution Approach 1:
The memory block is segmented into multiple decks, and the maximum start voltage delta is determined separately for each deck. This segmentation allows the system to account for voltage variations at the deck level, providing adaptability to local variations while keeping the control complexity manageable through modular organization.
Solution Approach 2:
Different maximum start voltage delta values are determined for different decks based on their specific characteristics. This local quality approach allows each deck to be optimized independently for its voltage variations, improving overall adaptability while maintaining relatively simple control logic at each local level.
Data Source
AI summary
Methods, systems, and apparatuses include sampling a memory subportion of a portion of memory, where the memory subportion includes multiple wordlines. A sampled voltage value for the memory subportion is determined based on the sampling. A maximum start voltage delta is received for the memory subportion, where the maximum start voltage delta is an estimated difference between the sampled voltage value and a lowest voltage value for the memory subportion. A start voltage to apply during programming of the memory subportion is determined using the sampled voltage value and the maximum start voltage delta.