Ramp settling assist circuit in local ramp buffer circuit
AssigneeOmniVision Technologies, Inc.
InventorsHiroaki Ebihara, Zhenfu Tian, Tao Sun, Liang Zuo, Yu-Shen Yang, Satoshi Sakurai, Rui Wang
Life of this patent
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Abstract
A ramp buffer circuit includes an input device having an input coupled to receive a ramp signal. A bias current source is coupled to an output of the input device. The input device and the bias current source are coupled between a power line and ground. An assist current source is coupled between the output of the input device and ground. The assist current source is configured to conduct an assist current from the output of the input device to ground only during a ramp event generated in the ramp signal.
Claims14
A ramp buffer circuit, comprising:
- an input device having an input coupled to receive a ramp signal;
- a bias current source coupled to an output of the input device, wherein the input device and the bias current source are coupled between a power line and ground;
- and
- an assist current source coupled between the output of the input device and ground, wherein the assist current source is configured to conduct an assist current from the output of the input device to ground only during a ramp event generated in the ramp signal.
An imaging system, comprising:
- an array of pixels to receive image light and generate an image charge voltage signal in response;
- and
- readout circuitry coupled to receive the image charge voltage signal from the array of pixels and provide a digital representation of the image charge voltage signal in response, the readout circuitry including a comparator to receive the image charge voltage signal, compare the image charge voltage signals to a ramp signal from a ramp generator, and provide the digital representation of the image charge voltage signal in response, wherein the comparator is coupled to receive the ramp signal through a ramp buffer circuit, wherein the ramp buffer circuit comprises:
- an input device having an input coupled to receive the ramp signal;
- a bias current source coupled to an output of the input device, wherein the input device and the bias current source are coupled between a power line and ground;
- and
- an assist current source coupled between the output of the input device and ground, wherein the assist current source is configured to conduct an assist current from the output of the input device to ground only during a ramp event generated in the ramp signal.
Dependencies are inferred from the claim text.