Flash Memory Dynamic Programming Circuit
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Solution Overview
Problem
In PMOS flash memory programming, the increasing threshold voltage of storage transistors leads to higher drain current, requiring larger layout areas and higher power consumption, and affects programming efficiency and reliability due to channel hot holes, which existing methods address inadequately by incrementally increasing control-line voltage.
Innovation Solution
A dynamic programming scheme that uses a current limiter and program voltage generator to maintain a constant drain current by adjusting the control-line voltage in response to changes in program current, ensuring the transistor operates in the channel hot electron region and minimizing channel hot hole effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control-line voltage is increased to compensate for increasing threshold voltage during programming, then the drain current can be maintained, but the layout area and power consumption increase
Solution Approach 1:
The patent applies dynamics by transitioning from fixed voltage levels to dynamic voltage adjustment. The control-line voltage is continuously adjusted during programming based on real-time drain current feedback, allowing the system to adapt to threshold voltage changes without requiring oversized circuitry or excessive power consumption.
Solution Approach 2:
The patent implements feedback control where the drain current is monitored during programming and used to adjust the control-line voltage. This closed-loop feedback mechanism ensures reliable programming by maintaining optimal current levels while avoiding the need for larger layout areas and higher power consumption that would be required with open-loop voltage increase methods.
2Reliability
If the control-line voltage is increased to compensate for increasing threshold voltage during programming, then the drain current can be maintained, but the power consumption increases
Solution Approach 1:
The system dynamically adjusts control-line voltage based on real-time conditions rather than using fixed high voltage levels. This dynamic adjustment maintains programming reliability by adapting to threshold voltage changes while consuming less power compared to continuously applying high voltage.
Solution Approach 2:
Feedback control monitors drain current and adjusts control-line voltage accordingly, ensuring reliable programming only when necessary. This prevents wasteful power consumption that would occur with continuous high voltage application, while still maintaining programming reliability through targeted voltage adjustment.
3Device complexity
If a fixed control-line voltage is applied during programming, then the circuit design is simple, but the channel hot hole effect increases and programming efficiency decreases
Solution Approach 1:
The patent implements dynamic control-line voltage adjustment that responds to programming conditions, thereby suppressing channel hot hole effects and improving programming efficiency. Although this increases circuit complexity compared to fixed voltage, the enhancement in programming efficiency justifies the added complexity.
4Reliability
If the control-line voltage is dynamically adjusted during programming, then the drain current can be constrained to a reference current, but the circuit complexity increases
Solution Approach 1:
The patent uses feedback control where drain current is monitored and used to adjust control-line voltage dynamically. This feedback mechanism constrains drain current to a reference current level, improving programming efficiency and reliability. The added circuit complexity is minimized by using efficient feedback control architecture.
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 reduces power consumption, decreases layout area requirements, enhances programming efficiency, and improves memory cell reliability by maintaining a constant gate current and constraining drain current.
Implementation Method 1
a program voltage generator, coupled to the control-line terminal and the data-line terminal, for generating the program voltage in response to the data-line signal, such that the program current tracks to the reference current
Data Source
AI summary
The present invention provides a flash memory including a memory cell, a current limiter and a program voltage generator. The memory cell is programmed in response to a program current and a program voltage. The current limiter reflects amount of the program current by a data-line signal, e.g., a data-line voltage. The program voltage generator generates and controls the program voltage in response to the data-line voltage, such that the program current can track to a constant reference current.