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US 8,941,618 B2Granted
Touch panel and driving method of the same
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorYoshiyuki Kurokawa
Life of this patent
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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.
Claims12
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, 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.
5 more elements
A driving method of a touch panel comprising the steps of:
- 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.
3 more elements
A semiconductor device comprising:
- 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.
5 more elements
A driving method of a semiconductor device comprising the steps of:
- 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.
3 more elements
Dependencies are inferred from the claim text.