Counter Latch Circuit Layout for High-Rate Image Sensor Readout
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Solution Overview
Problem
Existing semiconductor devices face challenges in achieving high-rate operations and simplifying layout designs, particularly in image sensor applications where correlated double sampling (CDS) methods are used.
Innovation Solution
The semiconductor device incorporates a first counter latch circuit and a second counter latch circuit, each with a series of latches that operate based on control signals, allowing for the latching and transmission of count codes and data codes in a manner that enables high-rate operations and simplified layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional counter latch circuits are used, then the device can process image data, but the layout becomes complex and high-rate operation is difficult to achieve
Solution Approach 1:
The patent merges the counter latch circuit and data latch circuit into a single integrated structure where both circuits share common signal lines and control mechanisms. The count code lines (CC0-CC3) and data code lines (DC0-DC3) are transmitted through shared transmission lines, reducing the overall number of separate connections and simplifying the layout while maintaining high-rate operation capability.
Solution Approach 2:
The latch circuits are designed with multi-functional tri-state inverters that can operate in different modes (latch mode and bypass mode) based on control signals. This universal design allows the same hardware structure to perform multiple functions: latching count codes, latching data codes, and bypassing signals when not needed, thereby reducing structural complexity while supporting high-rate operations.
2Reliability
If multiple separate latch circuits are used for count code and data code, then data processing is thorough, but the number of metal lines and loads increases
Solution Approach 1:
The patent combines the count code transmission lines and data code transmission lines into shared metal line structures. The same transmission lines carry both count codes and data codes at different time periods, reducing the total number of metal lines required while ensuring accurate data processing through sequential transmission and latching.
Solution Approach 2:
The circuit employs periodic transmission of count codes and data codes through the shared lines, controlled by timing signals. Count codes are transmitted during one period and data codes during another period, allowing thorough data processing without requiring separate permanent line structures for each signal type.
3Reliability
If conventional latch circuits without bypass capability are used, then data is reliably latched, but time delays increase
Solution Approach 1:
The tri-state inverters in the latch circuits are designed with dynamic control capability, allowing them to switch between latch mode and bypass mode based on control signals. When bypass mode is activated, signals pass through without the full latching delay, reducing time delays for non-critical paths while maintaining reliable latching when the latch mode is enabled for critical data.
Solution Approach 2:
The bypass capability allows critical timing signals to skip through the latch circuit structure without undergoing the complete latching process, thereby reducing time delays for signals that do not require latching while maintaining reliable data latching for signals that do require it.
Data Source
AI summary
Provided is a semiconductor device. The semiconductor device includes a first counter latch circuit configured to receive a count code and to latch the count code according to a comparison result signal; and a second counter latch circuit configured to receive the count code from the first counter latch circuit, and to latch the count code by using a plurality of first latches. The first latches are coupled in series to each other and are configured to operate to sequentially bypass values transmitted to the respective first latches.