Voltage generator circuit having a resistor ladder circuit and a switch control circuit allowing a variation of the slope of a given ramp wave, digital-to-analog converter, ramp generator circuit, analog-to-digital converter, image sensor system, and method for generating voltage
First Claim
1. A voltage generator circuit, comprising:
- a resistor ladder circuit configured to receive a predetermined voltage or a predetermined current, and to generate a plurality of reference voltages different from one another;
a plurality of switches corresponding to a plurality of taps of the resistor ladder circuit, each of which has one end connected to the tap corresponding thereto and the other end connected to an output node; and
a switch control circuit configured to control on-off states of the plurality of switches so that k (k is an integer greater than or equal to one) switches among consecutive (k+1) switches out of the plurality of switches are set to an ON state, and for switching the value of k,wherein said switching the value of k by said switch control circuit allows for a variation of the slope of a given ramp wave.
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Accused Products
Abstract
A resistor-ladder voltage generator circuit is provided, which controls so that k switches among consecutive (k+1) switches out of a plurality of switches connected to the resistor ladder circuit are simultaneously set to an ON state, and which temporally switches the value of k. This allows voltage waveforms having different slopes to be arbitrarily obtained, ranging from a voltage waveform having a small slope to a voltage waveform having a large slope, thereby improving the resolution of a generated voltage waveform without increasing the numbers of resistors and switches, while A/D conversion time is not increased even if the number of bits is increased. In addition, by using this voltage generator circuit as a ramp generator circuit, and by dynamically switching the slope of the ramp wave, acceleration of an image sensor is achieved.
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Citations
10 Claims
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1. A voltage generator circuit, comprising:
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a resistor ladder circuit configured to receive a predetermined voltage or a predetermined current, and to generate a plurality of reference voltages different from one another; a plurality of switches corresponding to a plurality of taps of the resistor ladder circuit, each of which has one end connected to the tap corresponding thereto and the other end connected to an output node; and a switch control circuit configured to control on-off states of the plurality of switches so that k (k is an integer greater than or equal to one) switches among consecutive (k+1) switches out of the plurality of switches are set to an ON state, and for switching the value of k, wherein said switching the value of k by said switch control circuit allows for a variation of the slope of a given ramp wave. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for generating a voltage in a voltage generator circuit which includes a resistor ladder circuit configured to generate a plurality of reference voltages different from one another, and a plurality of switches corresponding to a plurality of taps of the resistor ladder circuit, each of which has one end connected to the tap corresponding thereto and the other end connected to an output node,
wherein on-off states of the plurality of switches are controlled so that k (k is an integer greater than or equal to one) switches among consecutive (k+1) switches out of the plurality of switches are set to an ON state, and the value of k is sequentially switched, and wherein said switching the value of k allows for a variation of the slope of a given ramp wave.
Specification