Virtual Power Supply Test Module for IC Reliability
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Solution Overview
Problem
Integrated circuit devices face challenges in detecting errors in power grids and power gates due to process variations, which can result in improper power gating, leading to difficulties in qualification and increased testing costs.
Innovation Solution
A power grid test module is integrated into the integrated circuit device, which responds to a test signal to indicate whether the power grid and power gate are functioning correctly, using a small circuit that does not consume significant device area and allows for easy access to testing results via a standard interface, eliminating the need for expensive testing circuits or additional pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oscillator circuit is used to test the power grid and power gate, then the testing capability is provided, but the device area occupied is large and current leakage occurs when power gated
Solution Approach 1:
The patent extracts the essential testing function from the complex oscillator circuit and implements it using a simple test module that monitors the virtual power supply voltage directly. This extraction eliminates the need for large oscillator circuits while maintaining the ability to detect power grid and power gate errors.
Solution Approach 2:
Instead of using a physical oscillator circuit that consumes area and causes leakage, the patent creates a virtual test signal that copies the essential testing functionality through digital logic that monitors voltage levels, thereby achieving testing without the physical constraints of traditional oscillator-based methods.
2Ease of operation
If an external pin is added for measurement during testing, then the virtual power supply can be measured externally, but the cost increases due to expensive pin addition
Solution Approach 1:
The test module output can be connected to existing debug interfaces or test ports that serve multiple functions in the device, allowing the same pin to be used for both normal device operation and power grid testing, thereby eliminating the need for dedicated expensive test pins.
Solution Approach 2:
The device uses its own existing debug and test infrastructure to provide external access to test results, rather than requiring separate dedicated test pins. The test module integrates with the device's self-diagnostic capabilities, allowing external measurement through existing channels.
3Reliability
If traditional testing methods are used, then power grid operation can be tested, but expensive or undesirable testing circuits are required
Solution Approach 1:
The patent changes the testing approach from analog oscillator-based methods to digital voltage threshold detection. By monitoring whether the virtual power supply voltage exceeds a predefined threshold, the system achieves accurate testing using simple digital logic instead of complex analog testing circuits.
Solution Approach 2:
The test module uses simple, inexpensive digital logic components rather than expensive oscillator circuits or specialized test equipment. The testing functionality is implemented using basic voltage comparison logic that is cheap to manufacture and integrate into the device.
Data Source
AI summary
A power grid provides power to one or more modules of an integrated circuit device via a virtual power supply signal. A test module is configured to respond to assertion of a test signal so that, when the power grid is working properly and is not power gated, an output of the test module matches the virtual power supply. When the power grid is not working properly, the output of the test module is a fixed logic signal that does not vary based on the power gated state of the one or more modules.