Two-step single-slope comparator with high linearity and cmos image sensor including the same
AssigneeSK hynix Inc.
InventorHyeon-June KIM
Life of this patent
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Abstract
A comparator includes a first comparison block suitable for sampling a pixel signal, comparing a sampled pixel signal with a coarse ramping voltage, outputting a first comparison signal, sampling a coarse step voltage and outputting a residue voltage as a difference voltage between the sampled pixel signal and a sampled coarse step voltage; and a second comparison block suitable for comparing a fine ramping voltage with the residue voltage of the first comparison block and outputting a second comparison signal.
Claims13
A comparator, comprising:
- a first comparison block suitable for sampling a pixel signal, comparing a voltage of a sampled pixel signal to a coarse ramping voltage, outputting a first comparison result signal, sampling a coarse step voltage and outputting a residue voltage, representing a difference between the voltage of the sampled pixel signal and the sampled coarse step voltage;
- and
- a second comparison block suitable for comparing a fine ramping voltage to the residue voltage outputted by the first comparison block and outputting a second comparison result signal.
A complementary metal oxide semiconductor (CMOS) image sensor, comprising:
- a pixel array suitable for outputting a pixel signal corresponding to an incident light;
- a row decoder suitable for selecting and controlling pixels of the pixel array row by row according to a control signal of a controller;
- a ramp signal generator suitable for generating a coarse ramping signal and a fine ramping signal according to the control signal of the controller;
- a first comparison block suitable for sampling the pixel signal outputted from the pixel array, comparing a sampled pixel signal to the coarse ramping signal outputted by the ramp signal generator, outputting a first comparison result signal, sampling a coarse step voltage and outputting a residue voltage, representing a difference between a voltage of the sampled pixel signal and the sampled coarse step voltage;
- and
- a second comparison block suitable for comparing the fine ramping voltage outputted from the ramp signal generator to the residue voltage outputted by the first comparison block and outputting a second comparison result signal;
- a counter suitable for counting a clock of the controller according to the first comparison result signal outputted by the first comparison block and the second comparison result signal outputted by the second comparison block;
- a memory suitable for storing counting information of the counter according to the control signal of the controller;
- a column read-out circuit suitable for outputting data stored in the memory according to the control signal of the controller;
- and
- the controller suitable for controlling operations of the row decoder, the ramp signal generator, the first comparison block, the second comparison block, the counter, the memory, and the column read-out circuit.
A complementary metal oxide semiconductor (CMOS) image sensor comprising:
- a pixel array suitable for generating a pixel signal;
- a ramp signal generator suitable for generating coarse and fine ramping signals;
- a first comparison block suitable for generating a first comparison result signal by comparing the pixel signal to the coarse ramping signal;
- a second comparison block suitable for generating a second comparison result signal by comparing the fine ramping signal to a difference between the pixel signal and a coarse step signal;
- a counter suitable for counting a clock according to the first and second comparison result signals;
- and
- a column read-out circuit suitable for outputting a count result of the counter.
Dependencies are inferred from the claim text.