Input sensing device and display device including the same

1. An input sensing device comprising:

a sensor array comprising a plurality of electrodes;

an analog front-end circuit to process a first sensing signal and a second sensing signal provided from the sensor array; and

an analog-to-digital converter to generate sensor data in a digital format based on output signals of the analog front-end circuit,

wherein the analog front-end circuit comprises:

a charge amplifier to differentially amplify the first sensing signal and the second sensing signal to output a first differential signal and a second differential signal;

a demodulator to output in-phase signals corresponding to the first and second differential signals and to output quadrature signals corresponding to the first and second differential signals; and

a complex band-pass filter to filter the in-phase signals and the quadrature signals.

2. The input sensing device of claim 1 , wherein the analog front-end circuit further comprises a synthesizer connected to the complex band-pass filter, and is configured to synthesize the filtered in-phase signals and the filtered quadrature signals to generate a first real signal and a second real signal, and

wherein the first and second real signals are provided as the output signals.

3. The input sensing device of claim 2 , wherein the synthesizer comprises:

a phase shifter to shift a phase of the filtered quadrature signals by n/2; and

an adder to add one of the shifted quadrature signals to one of the filtered in-phase signals to generate the first real signal, and to add the other one of the shifted quadrature signals to the other one of the filtered in-phase signals to generate the second real signal.

4. The input sensing device of claim 1 , wherein:

the filtered in-phase signals and the quadrature signals are provided as the output signals of the analog front-end circuit; and

the analog-to-digital converter is configured to output the sensor data for only a positive frequency component or only a negative frequency component of the filtered in-phase signals and the filtered quadrature signals.

5. The input sensing device of claim 4 , wherein the sensor data includes a first sensed value corresponding to the filtered in-phase signals and a second sensed value corresponding to the filtered quadrature signals.

6. The input sensing device of claim 5 , further comprising a signal processor to sense an external input based on the sensor data,

wherein the signal processor comprises a synthesizer to digitally calculate the first sensed value and the second sensed value to generate a final sensed value.

7. The input sensing device of claim 6 , wherein the synthesizer comprises:

a delay circuit to delay the second sensed value by ¼ cycle; and

an adder to add the delayed second sensed value to the first sensed value to generate the final sensed value.

8. The input sensing device of claim 6 , wherein the synthesizer comprises an I-Q synthesizer.

9. The input sensing device of claim 4 , wherein the analog-to-digital converter comprises a complex delta-sigma analog-to-digital converter.

10. The input sensing device of claim 1 , wherein the complex band-pass filter comprises:

a first complex band-pass filter to filter the in-phase signals to provide filtered in-phase signals each including a positive frequency component or a negative frequency component; and

a second complex band-pass filter to filter the quadrature signals to provide the filtered quadrature signals each including the positive frequency component or the negative frequency component.

11. The input sensing device of claim 10 , wherein each of the first and second complex band-pass filters comprises a plurality of low-pass RC circuits, and

wherein the first complex band-pass filter and the second complex band-pass filter share resistors and capacitors.

12. The input sensing device of claim 1 , wherein each of the in-phase signals and the quadrature signals includes only a positive frequency component, or only a negative frequency component.

13. The input sensing device of claim 1 , wherein the analog front-end circuit further comprises a filter to filter the first differential signal and the second differential signal to generate a first filtered signal and a second filtered signal.

14. The input sensing device of claim 11 , wherein the demodulator comprises:

an oscillation circuit to output first local oscillation signals and second local oscillation signals orthogonal to the first local oscillation signals;

a first mixer circuit to apply the first local oscillation signals to the first and second filtered signals to output the in-phase signals; and

a second mixer circuit to apply the second local oscillation signals to the first and second filtered signals to output the quadrature signals.

15. The input sensing device of claim 11 , wherein the filter comprises a band-pass filter to pass both a positive frequency component and a negative frequency component for the first and second differential signals.

16. A display device comprising:

a display panel including pixels;

a sensor array comprising a plurality of electrodes;

an analog front-end circuit to process a first sensing signal and a second sensing signal provided from the sensor array; and

an analog-to-digital converter to generate sensor data in a digital format based on output signals of the analog front-end circuit,

wherein the analog front-end circuit comprises:

a charge amplifier to differentially amplify the first sensing signal and the second sensing signal to output a first differential signal and a second differential signal;

a demodulator to output in-phase signals corresponding to the first and second differential signals and to output quadrature signals corresponding to the first and second differential signals; and

a complex band-pass filter to filter the in-phase signals and the quadrature signals.