Memory Read Voltage Calibration Using Signal and Noise Estimation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional memory systems face inefficiencies in calibrating read voltages for memory cells due to shifts in threshold voltages caused by factors like charge loss and temperature changes, leading to high bit error rates and prolonged data retrieval latency through blind searching and multiple retry operations.

Innovation Solution

A memory subsystem that measures signal and noise characteristics to compute an optimized read voltage, allowing for efficient calibration and estimation of bit error rates, thereby improving data retrieval efficiency by scheduling hard and soft bit data reading together and selectively transmitting soft bit data based on error likelihood.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional blind searching and multiple retry operations are used to calibrate read voltages, then read voltage calibration can be performed, but data retrieval latency increases and bit error rates become high

Engineering Contradiction:

Improvebit error rateVSAvoiddata retrieval latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary measurement of signal and noise characteristics before actual data retrieval operations. By measuring characteristics at multiple test voltages and computing an optimized read voltage in advance, the system avoids the need for blind searching and multiple retry operations during actual data retrieval, thereby reducing latency while improving reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback from measured signal and noise characteristics to dynamically compute and adjust the optimized read voltage. The measurement results from test voltages are fed back into the optimization algorithm, which then adjusts the read voltage to minimize bit error rates, creating a closed-loop control system that adapts to changing conditions

Inventive Principle:

Principle #23Feedback

2Reliability

If soft bit data is always transmitted to assist decoding, then error recovery capabilities improve, but data transmission overhead increases

Engineering Contradiction:

Improveerror recovery capabilityVSAvoiddata transmission overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The system dynamically changes the parameter of data transmission by selectively transmitting soft bit data based on computed error likelihood. Instead of always transmitting or never transmitting soft bit data, the system adjusts this parameter based on the measured signal and noise characteristics, transmitting soft bit data only when the computed error probability exceeds a threshold, thereby optimizing the balance between error recovery capability and transmission overhead

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11562801B2Determine signal and noise characteristics centered at an optimized read voltage

Publication Date: 2023.01.24 MICRON TECHNOLOGY INC

AI summary

A memory device to estimate signal and noise characteristics of a group of memory cells in response to a command identifying the group of memory cells. For example, the memory device measures first signal and noise characteristics of the group of memory cells based on first test voltages, compute using the first signal and noise characteristics an optimized read voltage of the group of memory cells, and estimate, using the first signal and noise characteristics, second signal and noise characteristics of the group of memory cells, where the second signal and noise characteristics are based on second test voltages that are centered at the optimized read voltage of the group of memory cells.