Non-volatile Memory Read Sequence Power Optimization
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Solution Overview
Problem
Current non-volatile memory devices face challenges in reducing power consumption during sensing operations due to the need for multiple passes to resolve memory states, leading to increased power consumption as more memory cells conduct current.
Innovation Solution
A memory apparatus and method that identifies memory cells with threshold voltages below specific demarcation threshold voltages and applies near zero voltage to inhibit conduction currents, reducing power consumption by locking out irrelevant cells during read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If massively parallel sensing is performed to improve read performance, then read speed is improved, but power consumption increases due to compounded conduction current flow
Solution Approach 1:
The read operation is segmented into multiple passes, each targeting specific memory states. In each pass, only a subset of memory cells is actively sensed while others are locked out, dividing the massively parallel operation into smaller, power-efficient groups.
Solution Approach 2:
Memory cells are pre-identified and locked out based on their threshold voltage characteristics before the actual sensing operation. This preliminary action prevents unnecessary current flow in cells that will not contribute to the current read pass, reducing power consumption before reading begins.
2Measurement precision
If multiple sensing passes are executed to resolve all memory states, then measurement precision is improved, but power consumption increases due to repeated conduction current flow
Solution Approach 1:
Different voltage levels and sensing conditions are applied to different subsets of memory cells based on their specific threshold voltage ranges. Each pass is optimized for detecting specific memory states, allowing precise differentiation of all states while minimizing power consumption in each individual pass.
Solution Approach 2:
The sensing operation is performed periodically in discrete passes with alternating active and locked-out cell groups. Each pass targets specific memory states with appropriate demarcation voltages, and the periodic locking out of cells reduces cumulative power consumption across multiple passes.
3Productivity
If all memory cells are actively sensed in parallel, then productivity is improved, but power consumption increases due to compounded conduction currents
Solution Approach 1:
The parallel sensing operation is segmented into multiple groups of memory cells, with each group processed in a dedicated pass. This segmentation maintains high productivity within each pass while reducing the number of simultaneously active cells, thereby lowering power consumption.
Solution Approach 2:
Memory cells are pre-categorized and locked out based on their threshold voltage characteristics before each pass. This preliminary classification ensures that only the necessary subset of cells is actively sensed in parallel, maintaining productivity while reducing power consumption by excluding irrelevant cells from current flow.
Data Source
AI summary
A memory apparatus and method of operation are provided. The apparatus includes a page of memory cells connected to a plurality of word lines and arranged in strings and configured to retain a threshold voltage. A control circuit couples to the word lines and strings and identifies the memory cells having the threshold voltage less than a primary demarcation threshold voltage of a series for demarcating between memory states in a page read. The control circuit also identifies the memory cells having the threshold voltage less than a secondary demarcation threshold voltage of the series. The control circuit supplies a near zero voltage to the strings of the memory cells identified as having the threshold voltages less than at least one of the primary and secondary demarcation threshold voltages to inhibit conduction currents while identifying the memory cells having the threshold voltage less than a tertiary demarcation threshold voltage.