Touch panel and driving method of the same
First Claim
1. A touch panel comprising:
- a plurality of pixels each comprising a display element and a photo sensor; and
an A/D converter configured to be supplied with a first potential from the photo sensor, the A/D converter comprising an oscillation circuit and a counter circuit,wherein the oscillation circuit comprises a latch circuit,wherein the oscillation circuit is configured to generate a first signal having an oscillation frequency determined in accordance with the first potential, and to store a potential of the first signal in the oscillation circuit by applying a second potential to the latch circuit, the stored potential of the first signal being used as a potential of a least significant bit of the A/D converter,wherein the counter circuit is configured to generate a second signal having a discrete value determined in accordance with the oscillation frequency,wherein the oscillation circuit starts oscillating when a third potential is applied thereto, andwherein a period from when the oscillation circuit starts oscillating to when the first signal has a toggle is approximately half an oscillation cycle of the oscillation circuit.
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Accused Products
Abstract
It is an object to provide a touch panel which includes an A/D converter circuit and has a function of image shooting with high resolution and high-level gray scale and at high operation speed. A touch panel includes a plurality of pixels each provided with a display element and a photo sensor, an A/D converter to which a first potential is applied from a photo sensor, and a reading circuit. The A/D converter includes an oscillation circuit which changes the oscillating frequency of a first signal to be generated in accordance with the first potential and stops oscillating when a second potential is applied thereto from the reading circuit, and a counter circuit which generates a second signal having a discrete value determined in accordance with the oscillating frequency.
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Citations
12 Claims
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1. A touch panel comprising:
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a plurality of pixels each comprising a display element and a photo sensor; and an A/D converter configured to be supplied with a first potential from the photo sensor, the A/D converter comprising an oscillation circuit and a counter circuit, wherein the oscillation circuit comprises a latch circuit, wherein the oscillation circuit is configured to generate a first signal having an oscillation frequency determined in accordance with the first potential, and to store a potential of the first signal in the oscillation circuit by applying a second potential to the latch circuit, the stored potential of the first signal being used as a potential of a least significant bit of the A/D converter, wherein the counter circuit is configured to generate a second signal having a discrete value determined in accordance with the oscillation frequency, wherein the oscillation circuit starts oscillating when a third potential is applied thereto, and wherein a period from when the oscillation circuit starts oscillating to when the first signal has a toggle is approximately half an oscillation cycle of the oscillation circuit. - View Dependent Claims (2, 3)
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4. A driving method of a touch panel comprising the steps of:
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applying a first potential from a photo sensor included in each of a plurality of pixels to an A/D converter, generating a first signal by an oscillation circuit included in the A/D converter, the first signal having an oscillation frequency determined in accordance with the first potential, storing a potential of the first signal in the oscillation circuit by applying a second potential to a latch circuit, the stored potential of the first signal being used as a potential of a least significant bit of the A/D converter, and generating a second signal by a counter circuit included in the A/D converter, the second signal having a discrete value determined in accordance with the oscillation frequency after storing the potential of the first signal by applying the second potential to the latch circuit, wherein the oscillation circuit starts oscillating when a third potential is applied thereto, and wherein a period from when the oscillation circuit starts oscillating to when the first signal has a toggle is approximately half an oscillation cycle of the oscillation circuit. - View Dependent Claims (5, 6)
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7. A semiconductor device comprising:
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a plurality of pixels each comprising a photo sensor; and an A/D converter configured to be supplied with a first potential from the photo sensor, the A/D converter comprising an oscillation circuit and a counter circuit, wherein the oscillation circuit comprises a latch circuit, wherein the oscillation circuit is configured to generate a first signal having an oscillation frequency determined in accordance with the first potential, and to store a potential of the first signal in the oscillation circuit by applying a second potential to the latch circuit, the stored potential of the first signal being used as a potential of a least significant bit of the A/D converter, wherein the counter circuit is configured to generate a second signal having a discrete value determined in accordance with the oscillation frequency, wherein the oscillation circuit starts oscillating when a third potential is applied thereto, and wherein a period from when the oscillation circuit starts oscillating to when the first signal has a toggle is approximately half an oscillation cycle of the oscillation circuit. - View Dependent Claims (8, 9)
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10. A driving method of a semiconductor device comprising the steps of:
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applying a first potential from a photo sensor included in each of a plurality of pixels to an A/D converter, generating a first signal by an oscillation circuit included in the A/D converter, the first signal having an oscillation frequency determined in accordance with the first potential, storing a potential of the first signal in the oscillation circuit by applying a second potential to a latch circuit, the stored potential of the first signal being used as a potential of a least significant bit of the A/D converter, and generating a second signal by a counter circuit included in the A/D converter, the second signal having a discrete value determined in accordance with the oscillation frequency after storing the potential of the first signal by applying the second potential to the latch circuit, wherein the oscillation circuit starts oscillating when a third potential is applied thereto, and wherein a period from when the oscillation circuit starts oscillating to when the first signal has a toggle is approximately half an oscillation cycle of the oscillation circuit. - View Dependent Claims (11, 12)
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Specification