Voltage Passing Device for Low-Voltage Memory Read Operations
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Solution Overview
Problem
High threshold voltages in select transistors of nonvolatile memory cells lead to slow read operations and high power consumption due to the need for high voltages during the read process.
Innovation Solution
Incorporating a first voltage passing device and capacitance elements in the memory unit, which outputs different voltages for various operations, allowing the word line transistor to operate with lower voltages and reducing the threshold voltage, thereby speeding up the reading process and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If select transistors are made with high threshold voltages to enable high voltage operations, then the memory cell can perform program, erase, and inhibit operations, but the read operation requires high voltage which slows down the reading process and increases power consumption
Solution Approach 1:
The patent divides the transistor functionality by separating the select transistor from the word line transistor. The select transistor (with high threshold voltage) handles program/erase/inhibit operations, while the word line transistor (with low threshold voltage) handles read operations. This segmentation allows each transistor to be optimized for its specific function, resolving the contradiction between reliable high-voltage operation control and fast low-power reading.
2Reliability
If select transistors operate with high voltages, then they can control all memory cell operations, but power consumption increases during read operations
Solution Approach 1:
The patent segments the operation control functions between two transistors: the select transistor handles high-voltage program/erase/inhibit operations, while the word line transistor handles low-voltage read operations. This segmentation enables the reading process to use lower voltages, directly reducing power consumption while maintaining full operation control capability through the select transistor.
3Reliability
If high voltage is used during read operations, then the select transistor can maintain proper operation, but the reading process becomes slower
Solution Approach 1:
The patent segments the reading function from the high-voltage select transistor operation by introducing a dedicated word line transistor with low threshold voltage. This allows reads to be performed at low voltages with fast speed, while the select transistor maintains its high-voltage stability for program/erase/inhibit operations. The segmentation resolves the contradiction by assigning different voltage regimes to different operational phases.
4Device complexity
If the memory cell uses traditional select transistor configuration, then all operations are controlled by a single transistor, but circuit area increases when adding voltage passing devices
Solution Approach 1:
The patent merges the voltage passing function with the word line transistor by configuring the word line transistor and capacitance element as an integrated voltage control unit. This merging approach combines multiple functions (word line control, voltage passing, and capacitance coupling) into a unified structure that achieves the low-voltage reading capability without proportionally increasing circuit area, thus resolving the contradiction between functional complexity and area overhead.
Data Source
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AI summary
A memory cell (10) includes a floating gate transistor (FGT1), a word line transistor (WLT1) , a first capacitance element (110), a second capacitance element (120), and a first voltage passing device (130). The floating gate transistor (FGT1) has a first terminal for receiving a bit line signal (BL), a second terminal, and a floating gate. The word line transistor (WLT1) is coupled to the floating gate transistor (FGT1), receives a third voltage (GND), and is controlled by a word line signal (WL). The first capacitance element (110) is coupled to the first voltage passing device (130) and the floating gate, and receives a first control signal (CS1). The voltage passing device (130) outputs a second voltage (VZ) during an inhibit operation and a first voltage (VPP) during a program operation or an erase operation. With the voltage passing device, the reading time and the power consumption can both be reduced.