Non-volatile Memory Multi-Pass Sensing Power Optimization
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Solution Overview
Problem
Conventional non-volatile memory devices face challenges in achieving high performance and capacity while minimizing power consumption, particularly in multi-state sensing operations where precharge periods are lengthy and power consumption is high due to parallel sensing of multiple memory cells.
Innovation Solution
The solution involves minimizing the draining effect of memory cells during precharge by charging bit lines without coupling to the cells initially and reducing the precharge period, allowing bit lines to stabilize before sensing, and employing a two-pass sensing method to accurately identify and isolate high current cells, thereby reducing power consumption and improving sensing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If conventional precharge operation is used where bit lines are charged while coupled to memory cells, then the bit lines reach stable voltages for sensing, but power consumption is high due to the draining effect of memory cells during precharge
Solution Approach 1:
The patent applies preliminary action by performing the bit line precharge operation in two distinct phases: first charging the bit lines without coupling to memory cells (without draining effect), then coupling the bit lines to memory cells only after the precharge is complete. This sequencing eliminates the harmful draining effect during precharge while still achieving stable bit line voltages for accurate sensing.
2Quantity of substance
If multi-state sensing is performed by partitioning threshold window into multiple regions, then memory capacity is increased, but the number of sensing passes increases leading to higher power consumption
Solution Approach 1:
The patent segments the sensing operation into multiple passes, where each pass senses a specific partition of the threshold window. By dividing the sensing task into discrete segments (passes targeting different threshold regions), the system can efficiently handle multi-state memory while implementing power-saving measures in each individual pass, thereby managing overall power consumption for high-capacity sensing.
3Measurement precision
If precharge period is extended to ensure bit line stability, then sensing accuracy is improved, but power consumption increases due to prolonged operation
Solution Approach 1:
The patent performs the power-consuming precharge operation as a preliminary action before the actual sensing operation. By completing the bit line charging in advance (with or without memory cell coupling depending on the embodiment), the system ensures stable bit line voltages are established before sensing begins, thereby achieving high sensing accuracy while limiting the duration of high-power operation to only the precharge phase.
Data Source
AI summary
Power-saving techniques are employed in sensing a group of non-volatile memory cells in parallel. One technique is that the coupling of the memory cells to their bit lines is delayed during a precharge operation in order to reduce the cells' currents working against the precharge. Another technique is that a power-consuming precharge period is minimized by preemptively starting the sensing in a multi-pass sensing operation. High current cells not detected as a result of the premature sensing will still be able to be detected in a subsequent pass.