Data driver and driving method of organic light emitting display device using the same
A data driver capable of generating data signals with desired voltage values. The data driver includes a first digital-analog converter including a plurality of first switches, the first digital-analog converter selecting two reference voltages from among a plurality of reference voltages by turning on two of the first switches corresponding to high level bits of data; and a second digital-analog converter for dividing the two reference voltages into a plurality of voltages and for supplying any one of the two reference voltages and the divided voltages corresponding to low level bits of the data as a data signal to an output terminal, wherein the second digital-analog converter includes a transistor turned on by a bias voltage to compensate for a turn-on resistance of the two of the first switches.
1. A data driver comprising:
a first digital-analog converter including a plurality of first switches, the first digital-analog converter being adapted to select two reference voltages from among a plurality of reference voltages by turning on two of the first switches corresponding to high level bits of data; and
a second digital-analog converter for dividing the two reference voltages into a plurality of voltages and for supplying any one of the two reference voltages and the divided voltages corresponding to low level bits of the data as a data signal to an output terminal,
wherein the second digital-analog converter includes a transistor turned on by a bias voltage to compensate for a turn-on resistance of the two of the first switches.
2. The data driver as claimed in claim 1 , wherein the second digital-analog converter includes:
a plurality of voltage division resistors located between the two of the first switches, the plurality of voltage division resistors being adapted to divide the two reference voltages, and
a plurality of second switches located between a plurality of nodes of the voltage division resistors and the output terminal, the second switches being adapted to turn on corresponding to the low level bits of the data.
3. The data driver as claimed in claim 2 , wherein each resistance the voltage division resistors is set up to be substantially identical.
4. The data driver as claimed in claim 2 , wherein the transistor is installed between either one of the two of the first switches and the voltage division resistors.
5. The data driver as claimed in claim 4 , wherein a voltage level of the bias voltage is set such that a resistance of any one of the voltage division resistors is substantially identical to a turn-on resistance of the transistor summed with the turn-on resistance of the two of the first switches.
6. The data driver as claimed in claim 1 , wherein the data signal comprises a red data signal to be supplied to a red pixel, a green data signal to be supplied to a green pixel, and a blue data signal to be supplied to a blue pixel.
7. The data driver as claimed in claim 6 , wherein the transistor included in the second digital-analog converter for supplying the red data signal is supplied with a red bias voltage, the transistor included in the second digital-analog converter for supplying the green data signal is supplied with a green bias voltage, and the transistor included in the second digital-analog converter for supplying the blue data signal is supplied with a blue bias voltage.
8. The data driver as claimed in claim 7 , wherein the voltage values of the red, green, and blue bias voltages are set up to be different from one another.
9. The data driver as claimed in claim 1 , wherein the transistor is a PMOS type or an NMOS type.
10. The data driver as claimed in claim 2 , wherein each of the two of the first switches and each of the second switches are configured by connecting a PMOS type transistor and/or a NMOS type transistor in a transmission gate form.
11. The data driver as claimed in claim 1 , further comprising:
a shift register part for supplying a sampling signal;
a sampling latch part for storing the data in response to the sampling signal;
a holding latch part for storing the data stored in the sampling latch part; and
a data signal generation part for receiving the data from the holding latch part and for generating the data signal,
wherein each channel of the data signal generation part includes the first digital-analog converter and the second digital-analog converter.
12. The data driver as claimed in claim 11 , further comprising:
a level shifter located between the holding latch part and the data signal generation part, the level shifter being adapted to raise a voltage level of the data, and
a buffer for receiving the data signal from the data signal generation part.
13. An organic light emitting display device comprising:
a display region including a plurality of pixels connected to a plurality of scan lines and a plurality of data lines;
a scan driver for driving the scan lines; and
a data driver for driving the data lines,
wherein the data driver comprises:
a first digital-analog converter including a plurality of first switches, the first digital-analog converter being adapted to select two reference voltages from among a plurality of reference voltages by turning on two of the first switches corresponding to high level bits of data; and
a second digital-analog converter including a transistor turned on by a bias voltage with a voltage level to compensate for a turn-on resistance of the two of the first switches, a plurality of voltage division resistors for dividing the two reference voltages into a plurality of voltages, and a plurality of second switches for supplying any one of the two reference voltages and the divided voltages corresponding to low level bits of the data as a data signal to an output terminal.
14. The organic light emitting display device as claimed in claim 13 , wherein each resistance of the voltage division resistors is set to be substantially identical.
15. The organic light emitting display device as claimed in claim 14 , wherein the transistor is installed between either one of the two of the first switches and the voltage division resistors.
16. The organic light emitting display device as claimed in claim 15 , wherein the voltage level of the bias voltage is set such that a resistance of any one of the voltage division resistors is substantially identical to a turn-on resistance of the transistor summed with the turn-on resistance of the two of the first switches.
17. The organic light emitting display device as claimed in claim 13 , wherein the transistor is a PMOS type or an NMOS type.
18. The organic light emitting display device as claimed in claim 13 , wherein each of the two of the first switches and each of the second switches are configured by connecting a PMOS transistor and/or a NMOS type transistor in a transmission gate form.
19. The organic light emitting display device as claimed in claim 13 , wherein the data driver comprises:
a shift register part for supplying a sampling signal;
a sampling latch part for storing the data in response to the sampling signal;
a holding latch part for storing the data stored in the sampling latch part; and
a data signal generation part for receiving the data from the holding latch part and for generating the data signal,
wherein each channel of the data signal generation part includes the first digital-analog converter and the second digital-analog converter.
20. The organic light emitting display device as claimed in claim 19 , wherein
a level shifter is located between the holding latch part and the data signal generation part, the level shifter being adapted to raise a voltage level of the data, and
a buffer for receiving the data signals from the data signal generation part.
21. A driving method of an organic light emitting display device, the method comprising:
supplying a plurality of reference voltages to a first digital-analog converter;
selecting two reference voltages from among the plurality of reference voltages by turning on two of a plurality of first switches included in the first digital-analog converter corresponding to high level bits of data,
compensating for a turn-on resistance of the two of the first switches using a bias voltage level of a transistor included in a second digital-analog converter,
dividing the two reference voltages using a plurality of voltage division resistors included in the second digital-analog converter, and
supplying any one of the two reference voltages and the divided voltages as a data signal to an output terminal of the second digital-analog converter.
22. The driving method of an organic light emitting display device as claimed in claim 21 , wherein in the dividing of the two reference voltages, the voltage level of the bias voltage is set such that a resistance of any one of the voltage division resistors is substantially identical to a turn-on resistance of the transistor summed with the turn-on resistance of the two of the first switches.