Programmable Efuse Circuit With Separate Programming And Sensing Paths

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Solution Overview

Problem

Existing programming and sensing circuits for electrically programmable fuses in integrated circuits lack the ability to reliably and quickly sense the state of fuses without altering their programming, requiring advanced circuitry to manage high stress conditions and volatility issues.

Innovation Solution

The proposed efuse circuit includes a comparator for sensing the fuse status, switchable circuits for programming and sensing, and a reference voltage circuit, utilizing transistors and current sources to manage programming and sensing operations without interfering with each other, ensuring accurate and efficient state detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a sense circuit is used to detect the fuse state, then the fuse status can be sensed, but the sense circuit may alter the programming of the fuse

Engineering Contradiction:

Improvefuse state sensing accuracyVSAvoidfuse programming integrity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The circuit dynamically switches between programming mode and sensing mode using control signals. During sensing, the programming transistor is turned off to prevent interference, while during programming, the sensing path is disabled. This temporal separation allows the same circuit to perform both functions without compromising fuse integrity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

A control signal acts as an intermediary to manage the interaction between the sense circuit and programming circuit. The control signal coordinates the switching of transistors to ensure that sensing operations do not inadvertently trigger programming, thus protecting the fuse state while enabling accurate detection.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If advanced programming and sensing circuits are used, then fuse programming and sensing can be improved, but circuit complexity increases

Engineering Contradiction:

Improvefuse programming reliabilityVSAvoidprogramming and sensing circuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The circuit design uses shared components that serve multiple functions. The same transistor and circuit paths are used for both programming and sensing operations, controlled by different signal states. This multi-functionality reduces the need for separate dedicated circuits, thereby lowering overall complexity while maintaining reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The programming circuit and sensing circuit are merged into a single integrated structure where components are shared between the two functions. By combining these circuits and using control signals to manage their operation, the patent reduces component count and interconnection complexity while ensuring reliable fuse programming and sensing.

Inventive Principle:

Principle #5Merging (Combining)

3Speed

If sensing is performed quickly, then fuse state detection speed improves, but sensing accuracy may be compromised

Engineering Contradiction:

Improvefuse sensing speedVSAvoidfuse state detection accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The sensing operation uses periodic switching controlled by sense select signals that activate and deactivate the sensing path in controlled intervals. This periodic action allows the circuit to quickly sample the fuse state while maintaining stability through repeated measurements, achieving both speed and accuracy in fuse detection.

Inventive Principle:

Principle #19Periodic action

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 enables reliable and quick programming and sensing of electric fuses, maintaining their integrity under high stress conditions, and supports multiple fuses with distinct switch configurations for efficient state monitoring.

Implementation Method 1

a comparator for sensing a status of the fuse

Methodology Applied

Scientific EffectVoltage comparison:

Implementation Method 2

The first switch may include a transistor having a drain terminal coupled to the first terminal of the fuse, a gate terminal coupled to a program select signal, and a source terminal coupled to the ground supply

Methodology Applied

Scientific EffectElectrical switching:

Implementation Method 3

The switchable circuit may include a current source coupled to the second terminal of the fuse

Methodology Applied

Scientific EffectElectrical current generation:

Data Source

PatentUS7902903B2Programmable efuse and sense circuit

Publication Date: 2011.03.08 RAYTHEON CO

AI summary

A circuit for electric fuses includes circuits for sensing status and programming that have separate paths for each operation. The circuit includes a plurality of electrically programmable fuses and, associated with each fuse, a switch for coupling a first terminal of the fuse to a ground supply for programming or to a comparator for sensing. The circuit uses a switched current source to supply current to the fuses for programming. The comparator senses a fuse status when a current source is switched through the fuse. The comparator compares a voltage across the fuse and associated switches to a comparison voltage across a comparison resistor and switches included for matching.