Ramp signal generator and CMOS image sensor using the same
A ramp signal generator and a CMOS image sensor using the same are disclosed. The ramp signal generator includes a reference voltage generation unit that generates a reference voltage, a gain adjustment unit that adjusts a gain in cooperation with the reference voltage generation unit, a ramp bias voltage sampling unit that samples a ramp bias voltage of the gain adjustment unit, and a ramp signal generation unit that generates a ramp signal according to the ramp bias voltage sampled in the ramp bias voltage sampling unit.
1. A ramp signal generator comprising:
a reference voltage generation unit generating a reference voltage;
a gain adjustment unit adjusting a gain based on the reference voltage, and generating a ramp bias voltage based on the adjusted gain;
a ramp bias voltage sampling unit including a sampling switch that switches the ramp bias voltage according to a control signal and a sampling capacitor that samples the ramp bias voltage; and
a ramp signal generation unit generating a ramp signal according to the ramp bias voltage sampled by the ramp bias voltage sampling unit.
2. The ramp signal generator of claim 1 , wherein the ramp bias voltage sampling unit samples the ramp bias voltage by adjusting a ramp bias sampling time according to the control signal.
3. The ramp signal generator of claim 1 , wherein the ramp bias voltage sampling unit samples the ramp bias voltage during both of a comparator reset period and a ramping period.
4. The ramp signal generator of claim 1 , wherein the ramp bias voltage sampling unit samples the ramp bias voltage during a ramping period.
5. A CMOS image sensor comprising:
a pixel array generating a pixel signal corresponding to incident light;
a ramp signal generator generating a ramp signal that is obtained by sampling a ramp bias voltage by adjusting a ramp bias sampling time; and
a read-out circuit unit reading out the pixel signal of the pixel array according to the ramp signal to generate pixel data
wherein the ramp signal generator comprises:
a reference voltage generation unit generating a reference voltage;
a gain adjustment unit adjusting a gain based on the reference voltage, and generating the ramp bias voltage based on the adjusted gain;
a ramp bias voltage sampling unit including a sampling switch that switches the ramp bias voltage according to a control signal and a sampling capacitor that samples the ramp bias voltage sampling; and
a ramp signal generation unit generating the ramp signal according to the ramp bias voltage sampled by the ramp bias voltage sampling unit.
6. The CMOS image sensor of claim 5 , wherein the ramp bias voltage sampling unit samples the ramp bias voltage during both of a comparator reset period and a ramping period.
7. The CMOS image sensor of claim 5 , wherein the ramp bias voltage sampling unit samples the ramp bias voltage during a ramping period according to a control signal of an external control unit.