Multi-step pre-read voltage control for memory endurance
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Solution Overview
Problem
Memory devices face issues with energy consumption and endurance due to the use of single pre-read voltages, which can lead to excessive voltage cycling and false triggering of memory cells, potentially causing device failure and malfunctions, especially in critical applications like autonomous vehicles.
Innovation Solution
Applying multiple pre-read voltages dynamically to memory cells during write operations, where a first pre-read voltage is followed by a second pre-read voltage of greater magnitude if a significant number of cells do not snap, allowing the memory controller to customize the voltage application based on real-time conditions and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single pre-read voltage is applied to memory cells during write operations, then the operation is simple and fast, but energy consumption increases and endurance decreases due to excessive voltage cycling and false triggering
Solution Approach 1:
The pre-read voltage application is segmented into multiple discrete voltage levels (first pre-read voltage and second pre-read voltage of greater magnitude) applied in sequence. The controller segments the voltage cycling into conditional stages: initial pre-read at first voltage level, then conditional application of second voltage level based on whether cells snapped. This segmentation reduces unnecessary full-voltage cycling and associated energy consumption while maintaining operational effectiveness.
Solution Approach 2:
The voltage application scheme is made dynamic and adaptive rather than static. The controller dynamically determines whether to apply the second pre-read voltage of greater magnitude based on real-time detection of cell snapping status. This dynamic adjustment optimizes energy consumption by applying higher voltage only when necessary, rather than consistently applying maximum voltage to all cells during every write operation.
2Reliability
If a single pre-read voltage is used, then the operation is simple, but reliability decreases due to false triggering and potential device failure
Solution Approach 1:
The controller performs preliminary detection of cell snapping status after applying the first pre-read voltage before committing to the full write operation. This preliminary action allows the system to assess whether cells are ready for programming and prevents false triggering by conditionally applying the second pre-read voltage of greater magnitude only when needed. This preliminary assessment improves reliability by avoiding premature or inappropriate write operations.
Solution Approach 2:
The system implements feedback control by monitoring whether memory cells snap (change state) in response to the first pre-read voltage. Based on this feedback signal, the controller adaptively determines whether to proceed with applying the second pre-read voltage of greater magnitude. This feedback mechanism enhances reliability by ensuring write operations are performed only on cells that are ready, preventing false triggering and potential device failure.
3Duration of action of stationary object
If multiple pre-read voltages are applied dynamically, then energy consumption is reduced and endurance increases, but the control mechanism becomes more complex
Solution Approach 1:
The voltage application follows a periodic pattern with distinct phases: first pre-read voltage application, cell state detection, conditional second pre-read voltage application, then write operation. This periodic structure with clear phases simplifies control logic despite multiple voltage levels, as each phase has a specific function and duration. The rhythmic cycling through these phases improves endurance by systematically reducing unnecessary voltage stress on cells.
Data Source
AI summary
Systems, methods, and apparatus related to memory devices. In one approach, a memory device has a memory array including memory cells. A controller of the memory device applies multiple pre-read voltages to memory cells prior to performing write operations on the memory cells. The controller applies a first pre-read voltage to determine which of the memory cells have a sensed current that exceeds a threshold. In response to determining that a percentage of the memory cells exceeding the threshold is too low (e.g., below a fixed limit), the controller determines to apply a second pre-read voltage to the memory cells. The second pre-read voltage has a greater magnitude than the first pre-read voltage, and can be applied to ensure greater reliability in properly determining the existing programming state of the memory cells. The controller then applies write voltages to the memory cells as appropriate based on target logic states for each memory cell and the programming mode to be used by the controller.