Lidar Pixel Array Clocking for Transient Reduction
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Solution Overview
Problem
Lidar systems face issues with clock-induced transients and emissions, which degrade system performance and cause electromagnetic interference due to fast clock edges generating large supply current spikes.
Innovation Solution
The implementation of a pixel array where different pixels perform different tasks at varying phases or delays relative to each other, dispersing clock-induced transients and emissions throughout the clock cycle, thereby reducing their maximum amplitude. This involves grouping pixels to perform recurring tasks offset from each other and using phase-shifted clock signals to distribute supply current spikes across multiple temporal locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fast clock edges are used to facilitate accurate data transfers, then data transfer accuracy is improved, but supply current spikes and voltage transients increase causing electromagnetic interference
Solution Approach 1:
The pixel array is divided into multiple groups, with each group assigned to a different phase of the clock cycle. This segmentation distributes the clock-induced transients across multiple time segments, reducing the peak amplitude of supply current spikes while maintaining fast edge rates for accurate data transfers within each segment.
Solution Approach 2:
The system uses periodic clock cycles with multiple phases, where different pixel groups are activated in sequence during each cycle. This periodic distribution of tasks across phases allows fast clock edges to be used within each phase while the overall peak current is reduced through temporal spreading.
2Productivity
If all pixels perform the same task simultaneously, then processing efficiency is improved, but clock-induced transients reach maximum amplitude causing system degradation
Solution Approach 1:
The pixel array is segmented into multiple groups that perform different tasks in different phases of the clock cycle. This segmentation maintains high processing efficiency by ensuring all pixels are continuously utilized across phases, while distributing the transient generation across time to reduce peak amplitudes.
Solution Approach 2:
Tasks are distributed periodically across multiple clock phases, with each pixel group performing its assigned task during its designated phase. This periodic task distribution maintains overall processing throughput while reducing simultaneous transient generation through temporal separation.
3Device complexity
If clock signals are distributed to all pixels simultaneously, then system simplicity is maintained, but voltage transients on power supply lines increase degrading performance
Solution Approach 1:
The clock distribution is segmented into multiple phases, with each phase driving a specific group of pixels. This segmentation adds temporal complexity to the clock distribution but significantly reduces voltage transients by preventing simultaneous switching of all pixels, thereby improving system reliability.
Solution Approach 2:
Clock signals are distributed periodically across different phases to different pixel groups. This periodic distribution strategy increases clock management complexity slightly but dramatically reduces power supply noise and voltage transients, leading to improved system performance and reliability.
Data Source
AI summary
Circuits, methods, and apparatus that can reduce clock induced current and voltage transients and emissions in lidar pixel arrays. A pixel array can include an array of pixels, where at any given time, different pixels in the pixel array perform different tasks and are clocked by clock signals having different phases or delays relative to each other. This temporal dispersion of tasks and clock signals can spread clock induced current and voltage transients and emissions throughout a clock cycle, thereby reducing their maximum amplitude.