Method and system for generating a ramping signal

A method for generating a ramping signal comprising:

• applying a first enable signal to a series of storage circuits, each of the storage circuits including an input and an output, the output of a previous storage circuit being coupled to the input of a next storage circuit;
• applying a clock signal to the series of storage circuits, wherein the clock signal enables the series of storage circuits to propagate the first enable signal through the series of storage circuits;
• generating a first current signal based on the propagated first enable signal, wherein the first current signal increases every time when the first enable signal propagates through a storage circuit;
• converting the first current signal to a voltage signal to generate at least a first component of the ramping signal;
• comparing a column readout signal from a pixel to the ramping signal;
• and
• recording a value corresponding to the ramping signal when the comparing result changes.

A system for generating a ramping signal, the system comprising:

• a plurality of latches connected in series and configured to propagate a first enable signal based on a clock signal;
• a plurality of first current generating circuits coupled to outputs of the latches, the first current generating circuits being configured to generate a first current signal based on the propagated first enable signal;
• one or more second current generating circuits configured to generate a second current signal;
• and
• a load block coupled to the plurality of first current generating circuits and the one or more second current generating circuits, wherein the load block converts the first and second current signal to a voltage signal to generate the ramping signal, wherein a slope of the ramping signal is adjustable based on adjusting at least one of:
• the first current signal, a resistance of the load block, or a length of the ramping signal.