Flash Memory Block Selection Circuit With Shared High-Voltage Pass Transistors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flash memory devices require larger sizes to accommodate pass transistors durable against high voltages, increasing manufacturing costs due to the inclusion of one pass transistor per word line, which are vulnerable to program and erase voltages.
Innovation Solution
A block selection circuit with a series-connected pass transistor structure, utilizing a shared switch circuit to distribute high voltage stress across multiple transistors, reducing the size and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one pass transistor is used for each word line to ensure high voltage durability, then the reliability against high voltage is improved, but the area and manufacturing cost increase
Solution Approach 1:
The patent divides the single pass transistor function into multiple series-connected pass transistors (first pass transistor and second pass transistor). Each transistor handles a portion of the high voltage stress, allowing the use of smaller, lower-voltage-rated transistors while maintaining overall high voltage durability across the series combination.
Solution Approach 2:
The patent changes the voltage rating parameter of the pass transistors by connecting multiple lower-voltage transistors in series. The series connection allows transistors with lower individual voltage withstand capabilities to collectively handle higher voltages, reducing the area required for each transistor while maintaining system-level high voltage durability.
2Reliability
If the size of flash memory is enlarged to accommodate durable pass transistors, then the high voltage durability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent segments the high voltage handling function across multiple transistors, allowing the use of smaller, less expensive transistors that can be manufactured more easily. The series connection architecture enables cost-effective implementation by using standard lower-voltage transistors rather than requiring large, expensive high-voltage transistors.
Solution Approach 2:
The patent changes the voltage parameter requirements for the transistors by using series connection. This allows the use of transistors with lower voltage ratings that are cheaper to manufacture, while the series combination maintains the required high voltage durability for the overall block selection circuit.
3Area of stationary object
If multiple pass transistors are connected in series to reduce area, then the block selection circuit area is reduced, but the complexity of voltage control increases
Solution Approach 1:
The patent introduces switch circuits as intermediary components to control the gate voltages of the series-connected pass transistors. These switch circuits manage the complex voltage control requirements by selectively connecting power voltages to the appropriate transistor gates based on operation mode (read, program, erase), simplifying the overall control architecture.
Solution Approach 2:
The patent implements dynamic voltage control where the gate voltages of the pass transistors are adjusted based on the operation mode. During read operations, both transistors are turned on with appropriate voltages; during program and erase operations, the voltages are dynamically changed to protect unselected blocks while enabling high voltage application to selected blocks.
Data Source
AI summary
A block selection circuit of a flash memory, includes: a first pass transistor connected to an address decoder; a second pass transistor connected in series with the first pass transistor; a first driver circuit configured to control a gate voltage of the first pass transistor based on a first enable signal; a second driver circuit to control a gate voltage of the second pass transistor based on a second enable signal; a first switch circuit to provide a first power voltage or a second power voltage to a gate of the first pass transistor through the first driver circuit based on a first switch signal; and a second switch circuit to share a plurality of memory blocks and provide the first power voltage or the second power voltage to the first switch circuit.