Split-Gate Memory Sector Retirement Floating Control Gate
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Solution Overview
Problem
In split-gate memory designs, retired sectors are biased at a voltage greater than zero volts, creating an undesirable current path that lowers the shared supply voltage and can result in threshold voltage margin loss and read failures, which affects the endurance and yield of non-volatile memory systems.
Innovation Solution
A non-volatile memory system with a control gate driver that includes a latch circuit to float the output of retired sectors during read operations, preventing the formation of a current path and allowing for increased yield and program/erase cycling endurance by ignoring defective sectors without impacting active sectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If retired sectors are biased at voltage greater than zero volts, then the memory can be retired from service, but current path forms that lowers supply voltage and causes read failures
Solution Approach 1:
The patent extracts the harmful current path by disconnecting the retired sector's control gate from the shared supply voltage. The control gate driver output is left floating for retired sectors, effectively removing the source of the harmful current path while maintaining voltage bias for active sectors.
Solution Approach 2:
The patent applies different voltage bias conditions to different sectors based on their operational status. Active sectors receive proper voltage bias through the control gate driver, while retired sectors have their control gates left floating. This local differentiation eliminates current paths in retired sectors without affecting active sectors.
2Object-generated harmful factors
If control gate driver output is left floating for retired sectors, then current path is prevented, but voltage control is lost
Solution Approach 1:
The patent segments the control gate driver functionality by sector status. The driver circuit is divided into paths for active sectors (with voltage control) and retired sectors (floating). This segmentation allows precise voltage control where needed while eliminating harmful effects where not needed.
3Use of energy by moving object
If shared supply voltage is lowered due to current path, then power consumption decreases, but read voltage margin is lost
Solution Approach 1:
The patent converts the potential harm of having retired sectors connected to the supply (current paths) into a benefit by deliberately leaving them floating. This prevents current leakage that would lower the shared supply voltage, thereby maintaining sufficient read voltage margins while still allowing retired sectors to consume minimal power.
Data Source
AI summary
A memory is provided. The memory includes an array of non-volatile memory (NVM) cells arranged in a plurality sectors. A control gate driver circuit has an output coupled to control gates of the NVM cells in a sector in the plurality of sectors. An address decoder is coupled to the control gate driver circuit. And a latch circuit is coupled between the address decoder and the control gate driver circuit. The latch circuit stores a first value, and based on the stored first value, the control gate driver circuit output is floating.