LED Package DFT Scanning via Shared Data Stream
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Solution Overview
Problem
Current LED display systems face challenges in implementing design for test (DFT) scanning due to the need for additional ports and complex circuitry, which is not feasible in densely packed fine-pitch video displays.
Innovation Solution
The integration of an active electrical element within LED packages that can initiate DFT scanning using a same data stream for controlling LED chips, eliminating the need for separate ports by generating a test mode select (TMS) signal internally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate ports are added for DFT scanning, then testing capability is improved, but device complexity and port count increase
Solution Approach 1:
The data input port is designed to serve dual purposes: receiving normal LED control commands and receiving scan initiation commands for DFT scanning. The active electrical element includes a scanner that can operate in either normal LED control mode or test scanning mode, eliminating the need for separate dedicated test ports while maintaining both functionality and testing capability
2Area of moving object
If LED package size is reduced for fine-pitch displays, then pixel density is improved, but space for additional circuitry is reduced
Solution Approach 1:
The DFT scanning circuitry is merged with the existing active electrical element that controls the LED chips. The scanner shares the same physical space and electrical infrastructure as the LED control circuitry, integrating test functionality into the existing package without requiring additional discrete test components or increasing overall package size
Solution Approach 2:
The active electrical element is designed to perform multiple functions: normal LED chip control and DFT scanning operations. This multi-functionality allows the same physical components to serve both operational and testing purposes, eliminating the need for separate dedicated test circuitry that would increase package size
3Device complexity
If DFT scanning is implemented without separate ports, then device simplicity is improved, but testing functionality must be integrated into existing circuitry
Solution Approach 1:
The data input port and active electrical element are designed with multi-functionality, enabling them to handle both normal LED control operations and DFT scanning initiation. The scanner circuitry is configured to respond to scan initiation commands received through the same data input port used for LED control, eliminating the need for separate test ports while maintaining both functionality
Solution Approach 2:
The active electrical element dynamically switches between normal LED control mode and test scanning mode based on the type of command received. The scanner can be activated or deactivated depending on whether a scan initiation command is present in the data stream, allowing flexible operation without requiring separate dedicated hardware paths
Data Source
AI summary
Light-emitting devices and, more particularly, design for test (DFT) scanning in light-emitting diode (LED) packages and related methods are disclosed. LED packages include one or more LED chips and an active electrical element capable of initiating DFT scanning. The active electrical element may be configured to receive scan initiation commands via a same data stream that includes other commands and data for controlling operation of the one or more LED chips. By using a same data stream, the active electrical element and LED package may be configured to implement DFT scanning without requiring separate ports for receiving DFT specific signals. The active electrical element may generate a test mode select (TMS) signal that is internal to the active electrical element upon receipt of a scan initiation command, and the TMS signal is used to trigger DFT scanning within the active electrical element.