Fixed Discharge Bit Line Sensing for Multi-Bit Memory Cells
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Solution Overview
Problem
Traditional solid-state memory devices face inefficiencies in storing multiple bits per cell due to the need for multiple program and read operations, which become increasingly troublesome as more bits are stored, leading to longer operation times and higher power consumption.
Innovation Solution
The memory devices utilize a fixed discharge sensing scheme that generates a voltage signal representative of the actual threshold voltage of each memory cell across a continuum of possible threshold voltages, allowing for a single read operation to return a complete data value or bit pattern, rather than discrete bits, thereby reducing operation time and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple program and read operations are used to store multiple bits per cell, then data storage capacity is improved, but operation time and power consumption increase
Solution Approach 1:
The patent combines multiple read operations into a single operation by using a differential sensing approach that reads multiple bits simultaneously. The sense amplifier compares threshold voltages of multiple memory cells in parallel, allowing multiple bits to be retrieved in one operation rather than requiring separate read operations for each bit.
Solution Approach 2:
The sensing circuit is designed to perform multiple functions: it can read multiple bits from different memory cells simultaneously, determine their logical states through differential comparison, and output complete data values in a single operation. This multi-functional approach eliminates the need for multiple sequential read operations.
2Quantity of substance
If multiple program and read operations are used to store multiple bits per cell, then data storage capacity is improved, but power consumption increases
Solution Approach 1:
The patent merges multiple power-intensive read operations into a single operation. By using differential sensing that simultaneously evaluates multiple memory cells, the circuit reduces the total number of operation cycles and associated power consumption while maintaining the ability to retrieve multiple bits of data.
Solution Approach 2:
The differential sensing circuit automatically determines the logical states of multiple bits through direct voltage comparison, eliminating the need for multiple sequential operations. The circuit self-organizes to read multiple cells in parallel and directly outputs the complete data value, reducing overall power consumption.
3Measurement precision
If discrete bit reading is used, then data accuracy is maintained, but operation complexity increases
Solution Approach 1:
The patent combines multiple discrete bit readings into a single differential measurement operation. The sense amplifier simultaneously compares threshold voltages of multiple memory cells and directly outputs complete data values, reducing operational complexity while preserving data accuracy through the differential comparison method.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient storage and retrieval of multiple bits per cell with a single operation, significantly reducing operation times and power consumption while maintaining high reliability and data integrity.
Implementation Method 1
the bit line is allowed to discharge through a memory cell string including the target cell
Implementation Method 2
removing fixed units of charge from the bit lines of a memory array during a read operation
Data Source
AI summary
In one or more of the disclosed embodiments, a memory device is provided that reads a target memory cell by first charging the series string of memory cells to which the target memory cell is coupled. A fixed unit of charge is removed from the charged bit line. The bit line is sensed by sense amplifiers to determine the read voltage (i.e., threshold voltage) applied to a word line coupled to the target cell in order to turn on the target cell. The threshold voltage is indicative of the analog voltage stored on the target memory cell.