Solid-State Imaging Apparatus Overflow Handling Circuit
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Solution Overview
Problem
Existing solid-state imaging apparatus with built-in analog/digital conversion circuits face increased circuit scales and complexity due to the need for overflow handling, which complicates the reduction of circuit area.
Innovation Solution
A solid-state imaging apparatus with a reference signal generating circuit, comparators, memories, and a counter that writes digital data of a predetermined value to memories when signal values do not change during comparison, allowing for overflow handling without increasing circuit scales by simplifying the circuit configuration and eliminating the need for extra carry bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If extra bits for overflow or carry bits are provided in each column, then overflow handling capability is improved, but circuit area increases
Solution Approach 1:
The patent extracts the overflow handling function from the column-specific circuitry and implements it globally using a single overflow detection circuit that monitors all columns. Instead of adding carry bits to each column's data path, the system uses a centralized approach where the overflow detection circuit identifies overflow conditions across all columns and sets a common overflow flag, thereby eliminating the need for additional bits in each column while maintaining overflow handling capability.
Solution Approach 2:
The patent implements a universal overflow detection mechanism that serves all columns simultaneously. The overflow detection circuit performs a single function (detecting overflow) that applies to all column ADCs, and the resulting overflow flag is used universally to indicate overflow conditions regardless of which column experiences the overflow. This multi-functional approach allows one circuit to handle overflow for the entire array without requiring dedicated overflow handling circuitry in each column.
2Measurement precision
If AND circuit and OR circuit are provided for each column, then overflow detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the overflow detection logic from individual column circuits into a single centralized overflow detection circuit. Instead of having separate AND and OR circuits in each column, the system combines all overflow detection functions into one circuit that monitors the entire array. The overflow detection circuit uses logical operations to detect when any column experiences overflow, and this single detection mechanism replaces what would otherwise require multiple distributed circuits, thereby reducing overall device complexity while maintaining detection accuracy.
Data Source
AI summary
A solid-state imaging apparatus includes a plurality of pixels arranged two-dimensionally in a matrix, a reference signal generating circuit adapted to generate a ramp signal, a counter circuit adapted to perform a counting operation according to output of the ramp signal, comparators arranged on a column by column basis and adapted to compare signals read out of the pixels with the ramp signal, and memories arranged on a column by column basis and adapted to store digital data, wherein if output of the comparator is not changed during an AD conversion period, digital data of a predetermined value is stored in the memory. The solid-state imaging apparatus implements overflow handling using a simplified circuit configuration.