Semiconductor Memory Device Voltage Detector Power Loss Protection
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Solution Overview
Problem
Semiconductor memory devices face reliability issues due to incomplete program operations when external power supply voltage is suddenly interrupted, leading to unintended programming of memory cells during power off.
Innovation Solution
Incorporating a voltage detector to monitor the external power supply voltage and generate a detection signal when it falls below a reference level, triggering the discharge of the voltage applied to the drain selection line, thereby preventing unrequested programming during sudden power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a program operation is performed on memory cells using external power supply voltage, then data can be written to memory cells, but if the external power supply voltage is suddenly interrupted, the program operation may not be completed properly and unintended programming may occur
Solution Approach 1:
The voltage detector monitors the external power supply voltage before complete power loss occurs and generates a detection signal when the voltage drops below a reference level. This preliminary detection triggers the discharge of the drain selection line voltage before unintended programming can occur, preventing the harmful effect while allowing normal program operations to complete successfully
Solution Approach 2:
The invention applies a counter-action by discharging the drain selection line voltage in response to the detection signal when power supply voltage drops. This preliminary anti-action opposes the potential unintended programming that would occur during power interruption, thereby protecting the memory cells from harmful effects while maintaining reliable program operation completion
2Productivity
If voltage is applied to the drain selection line to couple memory cells to bit lines during program operation, then program operation can be performed, but if external power supply voltage is reduced, unrequested programming may occur
Solution Approach 1:
The voltage detector continuously monitors the external power supply voltage and provides feedback through the detection signal when the voltage drops below the reference level. This feedback mechanism enables the driving circuit to respond by discharging the drain selection line voltage, thereby preventing unrequested programming while maintaining normal program operation execution under adequate power conditions
3Ease of operation
If the voltage on the drain selection line is maintained during program operation, then memory cells remain coupled to bit lines for data writing, but during power interruption this maintains harmful voltage states leading to unintended programming
Solution Approach 1:
The invention makes the drain selection line voltage dynamic rather than static by automatically discharging it in response to the detection signal when power supply voltage drops. This dynamic adjustment allows the memory cells to remain coupled to bit lines during normal operation for ease of data writing, while automatically disconnecting and preventing harmful voltage states during power interruption that would cause unintended threshold voltage increases
Data Source
AI summary
A semiconductor memory device according to an embodiment of the present invention includes a memory block, a driving circuit performing a program operation on memory cells and a voltage detector generating a detection signal when an external power supply voltage is reduced to less than a reference voltage level. The driving circuit discharges a voltage applied to a drain selection line during the program operation in response to the detection signal.