Backpower-Safe Test Switch for ASIC Pin Multiplexing

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Solution Overview

Problem

Existing electronic devices face challenges in achieving high test coverage during final ASIC testing due to limited pins, and multiplexing analog test buses on existing ASIC pins risks backpowering the circuits when powered off.

Innovation Solution

Implementing backpower-safe test switches that maintain high impedance on communications bus package pins, preventing backpower of integrated circuits even when they are powered off, allowing multiplexing of analog test buses on existing ASIC pins.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If analog test bus is multiplexed on existing ASIC pins, then test coverage is improved, but risk of backpowering the ASIC increases

Engineering Contradiction:

Improvetest coverageVSAvoidbackpowering risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A test switch is introduced as an intermediary component between the test bus and the ASIC pin. This switch acts as a controlled gateway that allows test signals to pass through while preventing unauthorized power flow from the test bus back into the powered-off ASIC, thus enabling test coverage improvement without exposing the ASIC to backpowering risks.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The test switch is configured to be in a default off state that actively prevents backpowering before it can occur. By establishing this protective barrier in advance, the system allows multiplexing of the test bus on existing pins while preemptively blocking the harmful backpowering effect that would otherwise occur when the ASIC is powered off.

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If additional test pins are added to ASIC, then test coverage is improved, but device complexity increases

Engineering Contradiction:

Improvetest coverageVSAvoidpin count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Existing ASIC pins that were originally designed for specific functional purposes are made multi-functional by allowing them to also serve as test bus connections. The test switch enables these pins to be shared between their original function and test function, thereby improving test coverage without requiring additional pins and avoiding increased device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Use of energy by moving object

If ASIC is powered off during testing, then power consumption is reduced, but backpowering risk increases

Engineering Contradiction:

Improvepower consumptionVSAvoidbackpowering risk

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The test switch serves as a protective intermediary that allows the ASIC to remain powered off during testing (reducing power consumption) while simultaneously blocking any reverse power flow from the test bus that would otherwise backpower the ASIC. This enables low-power testing without exposing the powered-off ASIC to backpowering hazards.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12609697B2Backpower-safe test switch

Publication Date: 2026.04.21 INVENSENSE INC

AI summary

Disclosed embodiments provide backpower-safe test switches, devices, systems, and methods. By maintaining high impedance on an existing communications bus integrated circuit pin, disclosed embodiments prevent backpower of integrated circuits even when the integrated circuits are powered off. In a non-limiting aspect, disclosed embodiments facilitate increased final ASIC test coverage by facilitating multiplexing analog test bus on an existing ASIC pin.