VCSEL Driver Chip Abnormality Detection Through Collective Channel Sensing
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Solution Overview
Problem
Conventional technologies face difficulties in determining whether all channels in a VCSEL chip are normal due to the small size of microbump connection pads, making it challenging for a single driver chip to establish proper contact with test probes.
Innovation Solution
A driver chip with integrated drive and detection circuits, utilizing microbumps for electrical and mechanical connection, includes a detection circuit that uses pseudo-resistors and logic circuits to generate and compare operating voltages, enabling the driver chip to determine the normalcy of all channels through a collective determination signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If microbump connection pads are used to connect VCSEL chip to driver chip, then integration density is improved, but test probe contact becomes difficult
Solution Approach 1:
The connection pads are divided into two types: microbump connection pads for normal operation and test connection pads for testing. This segmentation allows the test function to be separated from the connection function, enabling test probes to access dedicated larger pads while microbumps maintain compact connections for light emitting elements.
Solution Approach 2:
Test connection pads serve as intermediary elements between test probes and the driver chip circuits. These pads act as accessible interface points that mediate the testing process without interfering with the microbump connections, allowing external test equipment to interact with internal circuitry.
2Measurement precision
If multiple separate test circuits are used for each channel, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
Multiple detection sections that would otherwise be separate test circuits are merged into a single integrated detection circuit on the driver chip. Each channel's detection functionality is combined while maintaining individual detection capability through shared common wiring and coordinated control signals.
Solution Approach 2:
The detection circuit is designed with multi-functional capability to handle testing for all channels through a unified structure. The circuit can selectively test different channels using common detection resources, making the test system universal rather than requiring dedicated separate circuits for each channel.
3Reliability
If detection circuit continuously monitors all channels, then reliability is improved, but power consumption increases
Solution Approach 1:
The detection circuit operates periodically rather than continuously, performing abnormality detection at specific intervals or under specific conditions. Control signals enable the detection function only when needed, allowing the circuit to remain inactive during normal operation and thus reducing overall power consumption while maintaining reliability.
Data Source
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Figure 2A~2B
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AI summary
A drive device according to the present disclosure includes a drive circuit (10) and a detection circuit (20). The drive circuit (10) drives a plurality of channels on an individual basis. The plurality of channels includes a plurality of light emitting elements (5). The detection circuit (20) collectively detects abnormalities of all the channels. Further, the drive device (10) is electrically and mechanically connected, with a plurality of microbumps (4), to a light emitting element array that includes the plurality of light emitting elements (5).