Multi-phase scanning

1. A method, comprising:

during each scanning stage, of a plurality of scanning stages, applying a same drive signal to each of a plurality of transmitter electrodes of a touch panel simultaneously for at least a period of time;

changing phase relations of the same drive signal, applied to each of the plurality of transmitter electrodes, according to the plurality of scanning stages, wherein changing the phase relations comprises:

applying the same drive signal having a first phase to a first one of the plurality of transmitter electrodes during a first scanning stage of the plurality of scanning stages, wherein the same drive signal has the first phase as an in-phase drive signal;

during the first scanning stage, applying the same drive signal having a second phase to a second one of the plurality of transmitter electrodes, wherein the same drive signal has the second phase as an opposite phase drive signal;

selecting a pseudorandom sequence having a number of one and negative one values, wherein a number of values in the pseudorandom sequence is equal to a number of the plurality of transmitter electrodes, wherein the one values correspond to the in-phase drive signal and the negative one values correspond to the opposite phase drive signal;

applying either the in-phase drive signal or opposite phase drive signal to the plurality of transmitter electrodes according to the pseudorandom sequence;

rotating the pseudorandom sequence; and

applying either the in-phase drive signal or opposite phase drive signal to the plurality of transmitter electrodes according to the rotated pseudorandom sequence;

for each scanning stage, receiving sense signals from a plurality of receiver electrodes, wherein each sense signal represents capacitances of intersections of the plurality of transmitter electrodes and a respective one of the plurality of receiver electrodes; and

using the phase relations of the same drive signal and the plurality of sense signals to detect a presence of an object on the touch panel.

2. The method of claim 1 , wherein said changing the phase relations further comprises:

applying the same drive signal having the second phase to the first one of the plurality of transmitter electrodes during a second scanning stage of the plurality of scanning stages; and

during the second scanning stage, applying the same drive signal having the first phase to the second one of the plurality of transmitter electrodes.

3. The method of claim 1 , wherein said changing the phase relations further comprises:

applying the same drive signal having a third phase to the first one of the plurality of transmitter electrodes during a second scanning stage of the plurality of scanning stages; and

applying the same drive signal having the third phase to the second one of the plurality of transmitter electrodes during a third scanning stage of the plurality of scanning stages.

4. The method of claim 1 , wherein said changing the phase relations comprises changing the phase relations using binary phase modulation, comprising:

receiving or generating a carrier signal as the same drive signal;

applying the carrier signal to the first one of the plurality of transmitter electrodes as the same drive having the first phase;

inverting the carrier signal to generate the same drive signal having the second phase; and

applying the inverted signal to the second one of the plurality of transmitter electrodes, wherein the inverted signal is opposite phase with the carrier signal.

5. The method of claim 1 , wherein the same drive signal having the first phase is an in-phase drive signal and the same drive signal having the second phase is an opposite phase drive signal, and wherein said changing the phase relations comprises:

selecting a pattern for the phase relations for the plurality of transmitter electrodes; and

according to the selected pattern, driving each of the plurality of transmitter electrodes with either the in-phase drive signal or the opposite phase drive signal

6. The method of claim 1 , wherein said changing the phase relations comprises:

applying in-phase drive signals to alternating ones of the plurality of transmitter electrodes; and

at the substantially same time as said applying the in-phase drive signals, applying opposite phase drive signals to the other alternating ones of the plurality of transmitter electrodes.

7. An apparatus comprising:

phase circuitry configured to simultaneously apply a same drive signal, for at least a period of time, to each of a plurality of transmitter electrodes of a touch panel during a plurality of scanning stages, wherein:

the plurality of scanning stages occur while the phase circuitry applies the same drive signal, the phase circuitry configured to provide phase modulation of the same drive signal applied to the plurality of transmitter electrodes according to the plurality of scanning stages;

the phase circuitry is configured to drive a first phase of the same drive signal on a first one of the plurality of transmitter electrodes during a first scanning stage of the plurality of scanning stages, and during the first scanning stage, the phase circuitry is configured to drive a second phase of the same drive signal on a second one of the plurality of transmitter electrodes;

the first phase of the same drive signal comprises an in-phase drive signal;

the second phase of the same drive signal comprises an opposite phase drive signal; and

the phase circuitry is configured to select a pseudorandom sequence having a number of one and negative one values, wherein a number of values in the pseudorandom sequence is equal to a number of the plurality of transmitter electrodes, wherein the one values correspond to the in-phase drive signal and the negative one values correspond to the opposite phase drive signal, the phase circuitry configured to applying either the in-phase drive signal or opposite phase drive signal to the plurality of transmitter electrodes according to the pseudorandom sequence, rotate the pseudorandom sequence, and apply either the in-phase drive signal or opposite phase drive signal to the plurality of transmitter electrodes according to the rotated pseudorandom sequence; and

sensing circuitry configured to receive sense signals from a plurality of receiver electrodes, wherein each sense signal represents capacitances formed between the plurality of transmitter electrodes and a respective one of the plurality of receiver electrodes, responsive to the same drive signal and to detect a presence of an object on the touch panel.

8. The apparatus of claim 7 , wherein the phase circuitry is configured to drive the second phase of the same drive signal on the first one of the plurality of transmitter electrodes during a second scanning stage of the plurality of scanning stages, and during the second scanning stage, drive the first phase of the same drive signal on the second one of the plurality of transmitter electrodes.

9. The apparatus of claim 7 , wherein the phase circuitry is configured to drive a third phase of the same drive signal on the first one of the plurality of transmitter electrodes during a second scanning stage of the plurality of scanning stages, and drive the third phase of the same drive signal on the second one of the plurality of transmitter electrodes during a third scanning stage of the plurality of scanning stages.

10. The apparatus of claim 7 , wherein the phase circuitry includes a binary phase modulation circuit configured to receive a carrier signal as the same drive signal, drive the first phase of the carrier signal on the first one of the plurality of transmitter electrodes, invert the carrier signal to generate the second phase of the same drive signal, and drive the second phase of the same drive signal on the second one of the plurality of transmitter electrodes.

11. The apparatus of claim 7 , wherein the phase circuitry is configured to apply in-phase drive signals to alternating ones of the plurality of transmitter electrodes, and at the substantially same time as the application of the in-phase drive signals, apply opposite phase drive signals to the other alternating ones of the plurality of transmitter electrodes.

12. The apparatus of claim 7 , wherein the phase circuitry is configured to select a pattern of phase modulation of the same drive signal and drive each of the plurality of transmitter electrodes with the same drive signal according to the selected pattern of phase modulation.

13. A system comprising:

a signal source configured to generate a carrier signal;

phase circuitry configured to receive the carrier signal and then drive the carrier signal at different phases simultaneously for at least a period of time, on each of a plurality of transmitter electrodes of a touch panel according to a plurality of scanning stages, wherein

the plurality of scanning stages occur while the phase circuitry drives the carrier signal;

the phase circuitry is configured to drive a first phase of the same drive signal on a first one of the plurality of transmitter electrodes during a first scanning stage of the plurality of scanning stages, and during the first scanning stage, the phase circuitry is configured to drive a second phase of the same drive signal on a second one of the plurality of transmitter electrodes;

the first phase of the same drive signal comprises an in-phase drive signal;

the second phase of the same drive signal comprises an opposite phase drive signal; and

the phase circuitry is configured to select a pseudorandom sequence having a number of one and negative one values, wherein a number of values in the pseudorandom sequence is equal to a number of the plurality of transmitter electrodes, wherein the one values correspond to the in-phase drive signal and the negative one values correspond to the opposite phase drive signal, the phase circuitry configured to applying either the in-phase drive signal or opposite phase drive signal to the plurality of transmitter electrodes according to the pseudorandom sequence, rotate the pseudorandom sequence, and apply either the in-phase drive signal or opposite phase drive signal to the plurality of transmitter electrodes according to the rotated pseudorandom sequence; and

sensing circuitry configured to receive sense signals from a plurality of receiver electrodes, wherein each sense signal represents capacitances formed between the plurality of transmitter electrodes and a respective one of the plurality of receiver electrodes, responsive to carrier signal driven at the different phases and to detect a presence of an object on the touch panel.

14. The system of claim 13 , wherein the phase circuitry is configured to drive a first phase of the carrier signal on a first one of the plurality of transmitter electrodes during a first scanning stage of the plurality of scanning stages, and during the first scanning stage, the phase circuitry is configured to drive a second phase of the carrier signal on a second one of the plurality of transmitter electrodes.

15. The system of claim 14 , wherein the phase circuitry includes a binary phase modulation circuit configured to receive the carrier signal, drive the first phase of the carrier signal on the first one of the plurality of transmitter electrodes, invert the carrier signal to generate the second phase of the carrier signal, and drive the second phase of the same drive signal on the second one of the plurality of transmitter electrodes.