Color Image Sensor AD Reference Circuit With Fewer Signal Lines
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Solution Overview
Problem
Existing analog-to-digital conversion methods for color image pickup in solid-state imaging devices require multiple signal lines for reference signals, exceeding the number of color components, leading to increased circuit complexity and noise.
Innovation Solution
A semiconductor device with a reference signal generating portion that generates a reference signal with a change property based on the color property of the filter, allowing fewer signal lines to transmit the reference signal to comparators, reducing circuit complexity and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple reference signal lines are used for each color component in AD conversion, then color control precision is improved, but circuit complexity increases
Solution Approach 1:
The patent merges the reference signal generation for multiple color components into a single reference signal line. Instead of providing separate reference signals for each color component (R, G, B), the invention uses one shared reference signal that is sequentially provided to comparators for different color components through time-division multiplexing, thereby reducing the number of reference signal lines from three to one while maintaining color control precision
Solution Approach 2:
The patent implements periodic action by sequentially providing the single reference signal to comparators for different color components in a repeating cycle. The reference signal is provided periodically to the R-component comparator, then to the G-component comparator, then to the B-component comparator, and repeats this sequence, enabling precise color control through time-division multiplexing without requiring multiple simultaneous reference signal lines
2Measurement precision
If multiple reference signal lines are used for each color component, then AD conversion accuracy is improved, but noise increases
Solution Approach 1:
The patent merges multiple reference signal lines into a single reference signal line that serves all color components sequentially. This consolidation reduces the total number of signal transmission paths, thereby reducing the cumulative noise from multiple lines while maintaining AD conversion accuracy through time-division multiplexing of the single reference signal to R, G, and B component comparators
3Adaptability or versatility
If separate reference signals are provided for each color component, then color property control is improved, but the number of signal lines exceeds color components
Solution Approach 1:
The patent uses periodic action to sequentially provide a single reference signal to comparators for different color components in a repeating sequence. The reference signal is provided periodically to the R-component comparator, then to the G-component comparator, then to the B-component comparator, enabling precise color property control for each component while reducing the number of physical signal lines from three to one through time-division multiplexing
Solution Approach 2:
The patent applies dynamics by making the reference signal connection dynamic rather than static. Instead of fixed dedicated reference signal lines for each color component, the system dynamically switches the single reference signal line to connect to different color component comparators at different time periods, enabling flexible color property control with reduced wiring
Data Source
AI summary
In a solid-state imaging device meeting color image pickup, which an AD converter is mounted on the same chip, the circuit scale and the number of transmission signal lines are reduced and a reference signal suitable for color image pickup is fed to an AD conversion comparing portion. DA converter circuits for two pixels of a repeat unit of a separation filter in the horizontal row direction in a unit of readout are prepared as a functional portion to generate a reference signal for AD conversion. The DA converter circuits generate the reference signals having a tilt in accordance with a color property and varying from an initial value based on a non-color property such as a black reference and a circuit offset. Each reference signal independently outputted from the DA converter circuits is basically directly transmitted through common signal lines to a voltage comparing portion which corresponds to color filters having a common color property through independent signal lines.