Image Sensor Readout Circuits Time-Domain Multiplexing Peak Power
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Solution Overview
Problem
Image sensors with large pixel arrays experience high peak to average power ratio (PAPR) due to readout circuits being in a static state for longer periods and active state for shorter periods, leading to undesirable power fluctuations and increased noise, costs, and physical implementation area.
Innovation Solution
Implementing time-domain multiplexing in readout operations across different pixel columns by activating readout circuits during offset time periods within a row time, allowing for pipelined sampling and processing operations to reduce peak power usage and mitigate high PAPR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If readout circuits operate in active state continuously, then power usage is stable and predictable, but peak power consumption increases and average power increases
Solution Approach 1:
The patent applies periodic action by implementing time-domain multiplexing where readout circuits are activated in periodic time slots rather than continuously. Different column readout circuits are enabled at different times during the row time period, creating a periodic activation pattern that distributes power consumption over time and reduces peak power while maintaining functional coverage.
Solution Approach 2:
The patent segments the readout operation by dividing the pixel array into multiple columns, each with its own readout circuit. By enabling only a subset of these segmented readout circuits at any given time (time-domain multiplexing), the system reduces the simultaneous power draw while ensuring all columns are serviced across the complete row time period.
2Power
If readout circuits are activated during offset time periods, then peak power usage is reduced, but readout operation complexity increases
Solution Approach 1:
The periodic activation pattern provides a structured and predictable sequence for enabling readout circuits. This regularity simplifies control logic compared to arbitrary activation schemes, as the timing and sequence of circuit enablement follow a repeating pattern that can be easily managed through systematic control signals.
Solution Approach 2:
The system dynamically adjusts which readout circuits are active at any given time, transitioning between different activation states. This dynamic control allows the system to optimize power consumption while maintaining the ability to service all pixel columns, with the dynamic behavior governed by a relatively simple time-multiplexing control mechanism.
Data Source
AI summary
An image sensor may include a pixel array having pixels arranged in rows and columns, column readout circuitry, and control circuitry. Column readout circuitry may include corresponding readout circuits each coupled to a corresponding column path for a respective column of pixels. The readout circuits may each include signal processing circuits such as correlated double sampling circuitry and analog-to-digital converter circuitry. To reduce peak-to-average power ratio, during the signal processing operations for each pixel row, the control circuitry may control the signal processing circuits to perform time-domain multiplexing across the pixel columns to activate the signal processing circuits at varied times within the row time. If desired, the pattern of time-domain multiplexing may be varied across the signal processing operations for different pixel rows and/or for different image frames.