Fingerprint sensor to support wake on finger and navigation
An input device for capacitive sensing includes: a plurality of transmitter electrodes and a plurality of receiver electrodes. The input device is configured to: operate in a first mode by driving sensing signals onto each of the transmitter electrodes and receiving separate detected signals corresponding to each of the plurality of receiver electrodes; and operate in a second mode by driving a common sensing signal onto a plurality of the transmitter electrodes and receiving a common detected signal corresponding to at least one receiver electrode selected from the plurality of receiver electrodes.
1. An input device for capacitive sensing, the input device comprising:
a plurality of transmitter electrodes; and
a plurality of receiver electrodes;
wherein the input device includes driver circuitry configured to:
operate in a first mode by driving sensing signals onto each of the transmitter electrodes and receiving separate detected signals corresponding to each of the plurality of receiver electrodes;
operate in a second mode by driving a common sensing signal onto a plurality of the transmitter electrodes and receiving a common detected signal corresponding to at least one receiver electrode selected from the plurality of receiver electrodes;
a plurality of differential receivers, configured to obtain the separate detected signals when operating in the first mode; and
at least one single ended receiver, configured to obtain the common detected signal when operating in the second mode;
wherein the input device is configured to use the plurality of differential receivers to obtain the separate detected signals when operating in the first mode and use the at least one single ended receiver to obtain the common detected signal when operating in the second mode.
2. The input device of claim 1 , wherein the common detected signal corresponds to a plurality of ganged receiver electrodes.
3. The input device of claim 1 , wherein the differential receivers subtract an average of capacitance values measured from at least two receiver electrodes from a receiver electrode of interest to obtain a detected signal of interest.
4. The input device of claim 3 , wherein the at least two receiver electrodes are ganged together and connected to an input terminal of an amplifier and subtracted from the receiver electrode of interest to obtain the detected signal of interest.
5. The input device of claim 1 , wherein an average capacitance of at least two receiver electrodes selected from the plurality of receiver electrodes are digitally subtracted from the capacitance of a receiver electrode of interest to obtain a detected signal of interest.
6. The input device of claim 1 , wherein the input device is further configured to obtain an image of a biometric object in a sensing area when operating in the first mode.
7. The input device of claim 1 , wherein the device is further configured to detect the presence of a biometric object in a sensing area including a first group of ganged receiver electrodes, when operating in the second mode.
8. The input device of claim 7 , wherein the first group of ganged receiver electrodes is located proximate to a center of a sensing area.
9. The input device of claim 1 , wherein the input device further comprises a plurality of groups of ganged receiver electrodes and wherein the input device is further configured to detect a movement of a biometric object in a sensing area when operating in the second mode with a first group of ganged receiver electrodes selected from the plurality of groups of ganged receiver electrodes.
10. The input device of claim 6 , wherein, when operating in the first mode, the input device drives sensing signals onto each of the transmitter electrodes and receives separate detected signals corresponding to each of the plurality of receiver electrodes repeatedly to image a biometric object.
11. The input device of claim 7 , wherein, when operating in the second mode, the input device repeatedly drives the common sensing signal onto the plurality of the transmitter electrodes and receives the common detected signal corresponding to the first group of ganged receiver electrodes until a biometric is detected.
12. The input device of claim 9 , further comprising:
when operating in the second mode,
repeatedly driving at least a second common sensing signal onto a second plurality of the transmitter electrodes and receiving a second common detected signal corresponding to a second group of ganged receiver electrodes; and
detecting a movement of a biometric from the plurality of the based on the common detected signal and second common detected signal.
13. The input device of claim 12 , wherein the common sensing signal and the second common sensing signal are driven in at least one of time multiplexed and code multiplexed manner.
14. The input device of claim 1 , further comprising:
during a first time when operating in the second mode,
detecting the presence of a biometric by repeatedly driving the common sensing signal onto the plurality of the transmitter electrodes and receiving the common detected signal corresponding to the first group of ganged receiver electrodes until the biometric is detected;
repeatedly driving at least a second common signal sensing signal onto a second plurality of the transmitter electrodes and receiving a second common detected signal corresponding to a second group of ganged receiver electrodes; and
detecting a movement of a biometric from the plurality of the based on the common detected signal and second common detected signal; and
when operating in the first mode the input device drives sensing signals onto each of the transmitter electrodes and receives separate detected signals corresponding to each of the plurality of receiver electrodes repeatedly to image a biometric object.
15. The input device of claim 1 , wherein the device is further configured to detect a force applied by a biometric object in a sensing area when operating in the second mode.
16. The input device of claim 1 , wherein the plurality of transmitter electrodes and the plurality of receiver electrodes form a transcapacitive sensor and the plurality of transmitter electrodes are orthogonal to the plurality of receiver electrodes.
17. An input device for capacitive sensing, the input device comprising:
a plurality of transmitter electrodes and a plurality of receiver electrodes;
wherein the input device includes driver circuitry configured to:
operate in a first mode by driving sensing signals onto each of the transmitter electrodes and receiving separate detected signals corresponding to a plurality of differential receivers, wherein each of the plurality of differential receivers is configured to provide a separate detected signal associated with one of the receiver electrodes; and
operate in a second mode by driving a sensing signal onto each of the transmitter electrodes and receiving at least one common detected signal at a single ended receiver, wherein the single ended receiver is configured to provide a common detected signal associated with at least one receiver electrode.
18. The input device of claim 17 , wherein the differential receivers subtract an average of capacitance values measured from at least two receiver electrodes from a receiver electrode of interest to obtain a detected signal of interest.
19. The input device of claim 18 , wherein the at least two receiver electrodes are ganged together and connected to an input terminal of an amplifier and subtracted from the receiver electrode of interest to obtain the detected signal of interest.
20. The input device of claim 17 , wherein an average capacitance of at least two receiver electrodes are digitally subtracted from the capacitance of a receiver electrode of interest to obtain a detected signal of interest.
21. The input device of claim 17 , further configured to obtain an image of a biometric object in a sensing area when operating in the first mode.
22. The input device of claim 17 , further configured to detect the presence of a biometric object in a sensing area including a first group of ganged receiver electrodes, when operating in the second mode, wherein the first group of ganged receiver electrodes are located near the approximate center of a sensing area.
23. The input device of claim 17 , wherein the processing system is configured to detect a movement of a biometric object in a sensing area including a plurality of groups of ganged receiver electrodes when operating in the second mode.
24. The input device of claim 17 , wherein the plurality of transmitter electrodes and the plurality of receiver electrodes form a transcapacitive sensor and the plurality of transmitter electrodes are orthogonal to the plurality of receiver electrodes.
25. A method of operating an input device for capacitive sensing, the input device comprising driver circuitry a plurality of transmitter electrodes and a plurality of receiver electrodes, the method comprising:
operating in a first mode, the first mode comprising:
driving sensing signals onto each of the transmitter electrodes;
receiving separate detected signals corresponding to each of a plurality of differential receiver electrodes, wherein each of the plurality of differential receivers is configured to provide a separate detected signal associated with one of the receiver electrodes;
operating in a second mode, the second mode comprising:
driving a common sensing signal onto each of the transmitter electrodes;
receiving a common detected signal corresponding to a first group of ganged single ended receiver electrodes, wherein each single ended receiver is configured to provide a common detected signal associated with at least one receiver electrode.
26. The method of claim 25 further comprising subtracting an average of capacitance values measured from at least two receiver electrodes from a receiver electrode of interest to obtain a detected signal of interest.