Flash Memory Bit Line Pre-Charge Voltage Stabilization
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Solution Overview
Problem
Conventional flash memory devices suffer from incorrect programming due to leakage current on bit lines, which causes adjacent memory cells to be inadvertently programmed.
Innovation Solution
A flash memory device with a pre-charge unit that includes a voltage stabilizing unit providing a stable current to bit lines, and a bias unit to control the voltage, ensuring that only the intended memory cell is programmed by maintaining the voltage on unrelated bit lines and preventing current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flash memory devices are used without pre-charge units, then the device structure is simpler, but programming errors occur due to leakage current on bit lines causing adjacent memory cells to be wrongly programmed
Solution Approach 1:
The pre-charge unit is activated before the programming operation to establish proper voltage levels on all bit lines. This preliminary action ensures that bit lines are in the correct initial state (pre-charged to a specific voltage) before programming begins, preventing leakage current from causing voltage drops that would lead to wrongful programming of adjacent cells.
Solution Approach 2:
The pre-charge unit acts as an intermediary component between the bit lines and the programming circuitry. It mediates the voltage control of bit lines by providing a stable reference voltage and controlling the pre-charge current, thereby isolating the bit lines from direct interference by leakage currents during programming operations.
2Manufacturing precision
If pre-charge units are added to stabilize bit line voltage, then programming accuracy is improved, but the device complexity increases due to additional components
Solution Approach 1:
The pre-charge unit is designed to serve multiple functions: it pre-charges all bit lines to a predetermined voltage, maintains voltage stability during programming operations, and can be controlled through existing control signals. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby limiting the increase in device complexity while achieving precise programming control.
3Reliability
If bit lines are pre-charged to predetermined voltage during pre-charge stage, then leakage current interference is prevented, but additional control circuits are required
Solution Approach 1:
The pre-charge control functionality is merged with the existing programming control circuitry. The pre-charge unit is controlled by the same control signals that manage the programming operation, combining multiple control functions into a unified control mechanism. This integration reduces the need for separate dedicated control circuits while ensuring reliable pre-charging and programming operations.
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
The solution effectively prevents interference with unprogrammed memory cells by maintaining the voltage on bit lines, improving programming accuracy and avoiding unintended programming.
Implementation Method 1
the voltage stabilizing unit includes a minor unit and a current source; wherein the minor unit includes an input PMOS transistor, and a plurality of minor PMOS transistors each of which corresponds to one of the adjusting transistors; wherein the input PMOS transistor includes a source coupled to a power supply, a drain and a gate which are coupled to each other and coupled to the current source
Implementation Method 2
a pre-charge unit, the pre-charge unit being coupled to a plurality of bit lines corresponding to the memory cells and pre-charging the plurality of bit lines to a predetermined voltage during a pre-charge stage
Implementation Method 3
each of the adjusting transistors includes a first end coupled to the voltage stabilizing unit, a second end coupled to a corresponding bit line and a control end coupled to the bias unit, and the bias unit is adapted for providing a bias voltage necessary to turn on the adjusting transistors
Data Source
AI summary
A flash memory device is provided. The flash memory device includes a memory cell array and a pre-charge unit. The pre-charge unit, coupled to a plurality of bit lines corresponding with the memory cell array, pre-charges the bit lines to a predetermined voltage during a pre-charge stage. The pre-charge unit includes a voltage stabilizing unit to provide a constant current to the bit lines. Due to the voltage stabilizing unit, in a programming process, the voltage applied to the bit lines which are not related with programming may not drop as a result of current leakage. Therefore, the memory cells except the memory cell to be programmed are kept in cut off state, without a current passing. As a result, interference with the memory cells which are not to be programmed may be effectively avoided and the accuracy of programming may be improved.