Test Diodes for Analog Fault Detection in Integrated Circuits

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Solution Overview

Problem

Conventional methods for testing analog faults in integrated circuits are inadequate, as they fail to detect faults that do not affect the circuit's functionality, leading to undetected defects that can cause malfunctions in vehicles and other applications.

Innovation Solution

Incorporating test diodes with anodes and cathodes coupled to internal analog nodes and a test pin, which remain inactive during normal operation, allowing for the detection of faults by applying a test voltage and measuring current flow to identify pull-up and pull-down faults without disrupting the circuit's operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional functional testing methods are used to test analog components, then the circuit functionality is tested, but faults that do not affect circuit functionality are not detected

Engineering Contradiction:

Improvefault detection capabilityVSAvoidfault coverage

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

Test diodes are introduced as intermediary components coupled to internal analog nodes. These diodes serve as mediators between the test equipment and the internal circuit nodes, enabling indirect observation of node states without disrupting normal circuit operation. The diodes convert internal node conditions into measurable current signals that reveal faults invisible to conventional functional testing.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The analog circuit is segmented by introducing separate test diodes for each internal analog node. Each diode independently monitors a specific node, dividing the complex analog circuit into individually testable segments. This segmentation allows targeted fault detection at specific nodes without requiring full circuit functionality, thereby improving fault coverage while maintaining circuit integrity.

Inventive Principle:

Principle #1Segmentation

2Reliability

If test diodes are added to detect internal analog node faults, then analog fault coverage increases to at least 85%, but device complexity increases

Engineering Contradiction:

Improveanalog fault coverageVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The testing function is extracted from the main circuit by using dedicated test diodes that are separate from the active circuit components. These diodes are taken out as independent testing elements that can be activated only during test mode, leaving the main circuit unchanged during normal operation. This extraction minimizes the impact on device complexity while achieving high fault coverage.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The test diodes remain inactive during regular circuit operation and are activated only periodically during test modes. This periodic activation allows the same physical infrastructure to serve dual purposes: normal circuit operation during most time periods and fault detection during test periods, thereby reducing the effective complexity impact while maintaining high reliability.

Inventive Principle:

Principle #19Periodic action

3Reliability

If test diodes are positioned on internal analog nodes for continuous monitoring, then fault detection capability improves, but area overhead increases

Engineering Contradiction:

Improvefault detection capabilityVSAvoidarea overhead

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

Multiple test diodes sharing common connections (such as shared test pins or common cathode/anode connections) are merged to reduce redundant structures. By combining test access points and utilizing shared pathways, the area required for testing multiple nodes is reduced while maintaining the ability to individually monitor each node through the shared infrastructure.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The test diodes and their associated test pins are designed to serve multiple functions: they enable testing of multiple different nodes, support both pull-up and pull-down fault detection, and can be used across different voltage domains. This multi-functionality reduces the need for dedicated testing structures for each node, thereby minimizing area overhead while maximizing fault detection capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 significantly increases analog fault coverage to at least 85%, providing reliable and repeatable fault detection with minimal interference and negligible area overhead, while ensuring the diodes are not active components during regular operation.

Implementation Method 1

When a test voltage is applied to the test pin, a flow of current at the one or more diodes detects the presence of a fault at the one or more internal analog nodes

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS10103074B2Method to improve analog fault coverage using test diodes

Publication Date: 2018.10.16 SEMICON COMPONENTS IND LLC

AI summary

Implementations of integrated circuits may include: one or more diodes each having an anode and a cathode, each of the one or more diodes may be coupled with a voltage domain. One or more test pins may be coupled with one or more diodes. The test pins may be configured to be coupled to a tester. The one or more diodes may be positioned on one or more internal analog nodes to detect the presence of one or more analog faults. The one or more diodes may be configured to remain inactive during regular operation of the integrated circuit.