CMOS Image Sensor Ripple Counter With Stable Count Shifting
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Solution Overview
Problem
Conventional CMOS image sensors face challenges in reducing chip size, preventing count value changes during operation switching, and increasing data transmission speed due to the size and complexity of up/down ripple counters and memory devices.
Innovation Solution
The implementation of a CMOS image sensor with a controller generating specific control signals to manage up/down ripple counters and memory chains, utilizing latches and switch blocks to prevent count value changes and enhance data transmission speed by serially shifting count values through memory chains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single ADC is used to convert analog pixel signals from all columns, then the chip size is reduced, but power consumption increases due to high-speed operation
Solution Approach 1:
The patent divides the ADC system into multiple column-parallel ADCs, where each ADC handles conversion for a specific column of pixel signals. This segmentation allows each ADC to operate at lower speed while maintaining overall system throughput, thus reducing power consumption while keeping chip size manageable through distributed architecture
Solution Approach 2:
The patent introduces a time-dimension solution by using sequential operation of multiple column-parallel ADCs. Instead of converting all columns simultaneously (spatial parallelism), the system converts columns sequentially over time, allowing the use of simpler, lower-power ADC designs while achieving the same overall conversion throughput
2Use of energy by stationary object
If multiple column-parallel ADCs are used, then power consumption is reduced, but the chip size increases
Solution Approach 1:
The patent merges multiple column-parallel ADC structures into a unified architecture that shares common resources such as reference voltage generators, clock circuits, and control logic. This merging approach reduces the total chip area required compared to having completely independent ADCs for each column, while still maintaining the power efficiency benefits of parallel operation
3Device complexity
If up/down ripple counters are used in ADCs, then the ADC structure is simplified, but count values change during operation switching between count and stop modes
Solution Approach 1:
The patent applies preliminary action by pre-setting the ripple counter to a known initial state (typically zero) before starting the conversion process, and by using control logic that ensures the counter is properly initialized and stabilized before mode switching occurs. This preliminary preparation prevents unintended count value changes during operation mode transitions
Solution Approach 2:
The patent implements feedback mechanisms where the state of the ripple counter is monitored and fed back to the control logic. When mode switching is detected, the feedback signal triggers corrective actions such as resetting the counter or holding its current value, thereby preventing unstable count value changes during transitions between count and stop modes
4Ease of manufacture
If conventional memory devices are used with up/down ripple counters, then the system is simple to implement, but data transmission speed is limited
Solution Approach 1:
The patent replaces conventional parallel data transmission mechanisms with a serial shifting architecture using shift registers. Instead of transmitting multiple data bits simultaneously through parallel buses (mechanical/electrical system), the system serially shifts data bits through sequential stages, which simplifies the transmission path and increases effective data transmission speed while maintaining ease of implementation with standard digital logic components
Data Source
AI summary
An example embodiment of an image sensor may include a controller and a plurality of up/down ripple counters. The controller may generate a first control signal and a second control signal. Each of the up/down ripple counters may perform a stop operation or a count operation in response to a corresponding one of a plurality of operation control signals generated based on at least in part on the first control signal. The count operation may be an up-count operation or a down-count operation based on the second control signal. The image sensor may also include a plurality of memory chains. Each of the memory chains may receive a count value output from the up/down counters and may shift the received count value in response to a third control signal and a fourth control signal output from the controller.