Ramp Wave Timing Control for Glitch-Free CMOS Image Sensors

The delay circuit is segmented into multiple delay units (first delay unit, second delay unit, third delay unit) that can be independently controlled. Each delay unit processes signals at different stages, allowing precise control over the timing of lower bit selection versus upper bit selection. This segmentation enables independent optimization of timing for each stage without affecting the entire circuit, thus achieving high timing precision while maintaining reasonable circuit complexity.

The delay units perform preliminary timing adjustment on the selection signals before they reach the current source cells. By pre-delaying the signals in controlled stages, the circuit ensures that the lower current source cells are selected before the upper current source cells, preventing timing conflicts and glitches. This preliminary action approach establishes correct timing relationships in advance, avoiding the need for complex real-time coordination mechanisms.

The delay control units are designed to dynamically adjust their delay characteristics based on operating conditions. The delay amount can be modified to optimize performance at different speeds, ensuring that the timing relationship between lower and upper bit selections remains correct even as operation speed varies. This dynamic adaptation maintains ramp wave stability across different productivity levels.

The circuit incorporates feedback mechanisms where the timing relationships are continuously monitored and adjusted. The delay control units receive feedback about the actual timing of signal transitions and adjust their delay amounts accordingly to maintain the required timing precision. This feedback ensures that even at high speeds, the stability of ramp wave generation is preserved by correcting any timing deviations that occur.

Instead of using a single large delay that would slow down the overall response, the delay is segmented into multiple smaller delay units. Each unit contributes a portion of the total delay, allowing the system to achieve the required timing precision through cumulative small delays rather than one large delay. This segmentation maintains faster response times while achieving the same timing precision.

The delay units are designed to provide just enough delay to establish correct timing relationships without excessive delay that would slow down the circuit. Each delay unit provides a partial delay amount that, when combined with other stages, achieves the required precision. This partial action approach avoids the performance penalty of over-delaying while still achieving sufficient timing precision for stable operation.