OTP Read Bias Current Mirror for Post-Programming Reliability
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Solution Overview
Problem
Conventional OTP memory devices using the anti-fuse method face reading failures due to increased resistance values after programming, as the same bias current used for programming is also employed for reading, leading to reliability issues during read operations.
Innovation Solution
A circuit and method that generate multiple current levels using a current mirror system with transistors, allowing for selective bias current supply during programming and reading operations, enabling different current values to be used based on external input currents and varying transistor sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same bias current is used for both programming and reading operations, then the device complexity is reduced, but the reliability deteriorates due to reading failures after programming
Solution Approach 1:
The bias current generation is segmented into multiple current levels (first bias current for programming, second bias current for reading). The current generation unit generates multiple discrete current levels that can be selectively applied to different operational stages, separating the programming and reading current requirements to eliminate read failures while maintaining manageable device complexity.
Solution Approach 2:
The bias current is made dynamic rather than static. The control unit dynamically selects and switches between different bias current levels based on the operational state (programming or reading). This dynamic adaptation allows the system to optimize current levels for each operation type, improving reliability without requiring completely separate current generation circuits.
2Manufacturing precision
If a high bias current is used during programming to destroy gate oxide materials, then the programming effectiveness is improved, but the resistance value increases causing reading failures
Solution Approach 1:
The system performs preliminary action by generating and storing multiple bias current levels in advance before the actual programming or reading operations. The current generation unit prepares the appropriate current levels, and the control unit selects the correct pre-prepared current level based on the operational requirement, ensuring that high current is available for programming and low current for reading without real-time conversion delays.
Solution Approach 2:
The bias current parameter is changed according to the operational stage. The system changes the current level parameter from high (for programming) to low (for reading) based on the control signal. This parameter change approach allows the same physical circuit to adapt to different operational requirements by simply changing the current level, effectively solving the contradiction between programming effectiveness and reading reliability.
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 prevents reading failures by ensuring appropriate current levels for verifying programming and subsequent read operations, maintaining reliability even with varying resistance values, thus enhancing the operational stability of OTP memory cells.
Implementation Method 1
A circuit and method that generate multiple current levels using a current mirror system with transistors, allowing for selective bias current supply during programming and reading operations
Data Source
AI summary
Provided is a circuit for generating a bias current, which includes a current generation unit including a plurality of current mirrors that generate a plurality of currents having different levels. The circuit also includes a current generation control unit that controls the generating the plurality of current having different levels in the current generation unit based on an externally input current. The circuit further includes a current supplying unit that supplies a current selected from the plurality of currents having different levels to an external device.