Ramp generator and image sensing device
AssigneeNovatek Microelectronics Corp.
InventorsYueh-Ru Lee, Pai-Hsiang Hsu
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Abstract
A ramp generator includes a digital-to-analog converter, a first capacitor, a second capacitor and a noise cancellation circuit. The digital-to-analog converter is configured to generate a ramp-up voltage signal on a first output terminal and a ramp-down voltage signal on a second output terminal. The first capacitor is coupled between the first output terminal and an intermediate node. The second capacitor is coupled between the second output terminal and the intermediate node. The noise cancellation circuit is coupled with the intermediate node. The noise cancellation circuit is configured to provide a compensation feedback according to an intermediate voltage on the intermediate node.
Claims18
A ramp generator, comprising:
- a digital-to-analog converter, having a first output terminal and a second output terminal, and configured to generate a ramp-up voltage signal on the first output terminal and a ramp-down voltage signal on the second output terminal;
- a first capacitor, coupled between the first output terminal and an intermediate node;
- a second capacitor, coupled between the second output terminal and the intermediate node;
- and
- a noise cancellation circuit, coupled with the intermediate node, and configured to provide a compensation feedback according to an intermediate voltage on the intermediate node, wherein the compensation feedback is correlated to an alternating-current component of the intermediate voltage, the compensation feedback is configured for compensating an intrinsic noise of the digital-to-analog converter.
An image sensing device, comprising:
- a ramp generator, configured to generate a ramp output signal, wherein the ramp generator comprises:
- a digital-to-analog converter, having a first output terminal and a second output terminal, and configured to generate a ramp-up voltage signal on the first output terminal and a ramp-down voltage signal on the second output terminal, wherein the ramp output signal is generated according to the ramp-up voltage signal or the ramp-down voltage signal;
- a first capacitor, coupled between the first output terminal and an intermediate node;
- a second capacitor, coupled between the second output terminal and the intermediate node;
- and
- a noise cancellation circuit, coupled with the intermediate node, and configured to provide a compensation feedback according to an intermediate voltage on the intermediate node, wherein the compensation feedback is correlated to an alternating-current component of the intermediate voltage, the compensation feedback is configured for compensating an intrinsic noise of the digital-to-analog converter;
- and
- an image readout circuit, coupled to the ramp generator and a photoelectric sensing pixel, the image readout circuit is configured to sample a pixel sensing voltage from the photoelectric sensing pixel in reference with the ramp output signal from the ramp generator, so as to generate a digital output signal.
Dependencies are inferred from the claim text.