Fuse Sense Circuit for OTP Memory State Sensing
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Solution Overview
Problem
Conventional one-time programmable (OTP) memory technologies face challenges with long burning times, large physical space requirements, and limited flexibility in assigning fuse states to logical values due to the small resistance margin between unblown and blown polyfuses, leading to impractical power consumption and reliability issues in differentiating between fuse states.
Innovation Solution
The implementation of a fuse sense circuit that compares a sense voltage to a reference voltage to determine the state of polyfuses, using a resistive element and comparator to provide a signal indicative of the fuse state, allowing for simultaneous sensing of multiple fuses and reducing power consumption by optimizing the resistance values of the resistive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional polyfuse resistance values are used for OTP memory, then the fuse can be programmed, but the small resistance margin between unblown and blown states causes difficulty in reliably differentiating fuse states
Solution Approach 1:
The patent changes the resistance parameter by using a resistive element with a specific resistance value (e.g., 1.65 kΩ) that is significantly different from both the unblown polyfuse resistance (110-220 Ω) and blown polyfuse resistance (≥880 Ω). This parameter change creates well-separated voltage levels that can be reliably differentiated by the comparator, resolving the measurement precision and reliability contradiction.
2Productivity
If high current is provided to polyfuse for programming, then the fuse transitions to blown state, but the burning time is long
Solution Approach 1:
The patent uses a resistive element with resistance significantly higher than the polyfuse resistance, which limits the current to a partial level (not excessive high current). This partial action approach achieves fuse programming while significantly reducing the burning time compared to conventional high current methods, resolving the productivity and duration contradiction.
3Productivity
If OTP memory arrays are implemented with conventional approaches, then memory function is achieved, but large physical space is required in the device
Solution Approach 1:
The patent merges the sensing function and the reference voltage generation function into a single resistive element. The resistive element serves dual purposes: providing a reference voltage for comparison and enabling current limiting during programming. This merging eliminates the need for separate reference voltage circuits, reducing the physical area of the OTP memory array and resolving the productivity and area contradiction.
4Measurement precision
If conventional sensing methods are used for fuse states, then fuse state can be determined, but power consumption is impractical
Solution Approach 1:
The patent uses periodic action by enabling the sensing circuit only when needed (during read operations) and keeping it disabled during programming and idle periods. The resistive element provides reference voltage only when the sensing circuit is active, significantly reducing overall power consumption while maintaining measurement precision when sensing is required, resolving the measurement precision and power consumption contradiction.
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 enables efficient and reliable sensing of fuse states, reducing the physical size of OTP memory arrays, decreasing programming time, and providing flexibility in assigning logical values to fuse states, while minimizing power consumption.
Implementation Method 1
The unblown state may be characterized by a low resistance value, and the blown state may be characterized by a high resistance value
Implementation Method 2
a resistive element and comparator to provide a signal indicative of the fuse state
Implementation Method 3
providing the high current may vaporize a portion of the fuse, such as a metal silicide (e.g., WSi or CoSi2) layer
Data Source
AI summary
Apparatuses and methods for sensing fuse states are disclosed herein. An apparatus may include an array having a plurality of sense lines. A plurality of cells may be coupled to a sense line of the plurality of sense lines. A fuse sense circuit may coupled to the sense line of the plurality of sense lines and configured to receive a sense voltage from a cell of the plurality of cells. The sense voltage may be based, at least in part, on a state of a fuse corresponding to the cell of the plurality of cells. The fuse sense circuit may further be configured to compare the sense voltage to a reference voltage to provide a fuse state control signal indicative of the state of the fuse.