Dynamic Non-Selected Word Line Voltage for Memory Power Reduction

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Solution Overview

Problem

Current memory devices experience higher supply current during reads on partially-programmed and fully-erased blocks due to fixed non-selected word line voltage, which is not optimized based on the number of programmed word lines, leading to inefficiencies in power consumption.

Innovation Solution

A controller is configured to determine the last written word line in a memory block and adjust the non-selected word line voltage accordingly, reducing the voltage based on the word line load to minimize peak and average supply current during reads without impacting performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a fixed non-selected word line voltage is applied during reads, then read operations can be performed on all block types, but supply current is excessively high during reads on open and erased blocks

Engineering Contradiction:

Improvesupply currentVSAvoidread compatibility across block types

Core Design Contradiction:

Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The non-selected word line voltage is changed from a fixed value to a dynamic value that adjusts based on the block type (closed, open, or erased). The controller determines the block type and applies different voltage levels accordingly, allowing the system to optimize power consumption for each specific read scenario while maintaining read capability across all block types

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Different voltage levels are applied to non-selected word lines based on the local characteristics of the memory block being read. Closed blocks receive a lower voltage while open and erased blocks receive appropriately adjusted voltages, tailoring the electrical characteristics to the specific state of each block rather than using a uniform approach

Inventive Principle:

Principle #3Local quality

2Use of energy by moving object

If the non-selected word line voltage is reduced to lower supply current, then power consumption decreases, but read performance may be compromised

Engineering Contradiction:

Improvepower consumptionVSAvoidread performance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The voltage parameter is dynamically adjusted based on the block type to achieve optimal power-performance balance. By changing the voltage level according to whether the block is closed, open, or erased, the system reduces power consumption for erased blocks (which have higher leakage) while maintaining sufficient voltage for reliable reads on closed blocks

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11521688B2Power reduction during open and erased block reads of memory based on the position of last written word line of a memory block

Publication Date: 2022.12.06 SANDISK TECHNOLOGIES LLC

AI summary

A data storage device including, in one implementation, a non-volatile memory and a controller. The non-volatile memory includes a memory block. The memory block includes a plurality of word lines that are written sequentially from a first end of the memory block to a second end of the memory block. The controller is coupled to the non-volatile memory. The controller is configured to determine a last written word line of the memory block. The controller is also configured to set a non-selected word line voltage based on the last written word line of the memory block. The controller is further configured to apply the non-selected word line voltage to non-selected word lines of the memory block.