Single-chip multi-stimulus sensor controller

• US 10,042,472 B2
• Filed: 07/24/2017
• Issued: 08/07/2018
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Hotelling, Steven Porter, Krah, Christoph Horst, Yousefpor, Marduke, Wilson, Thomas James
• Primary Examiner(s): Lee, Jr., Kenneth B
• Application Number:
  US15/658,314
• Publication Number:
  US 20170322669A1
• Time in Patent Office: 379 Days
• Field of Search: None
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G09G 5/18 Timing circuits for raster scan displays specially adapted for television H04N ; synchronisation between the display unit and other display units, videodisc player G09G5/12

Abstract

A multi-stimulus controller for a multi-touch sensor is formed on a single integrated circuit (single-chip). The multi-stimulus controller includes a transmit oscillator, a transmit signal section that generates a plurality of drive signals based on a frequency of the transmit oscillator, a plurality of transmit channels that transmit the drive signals simultaneously to drive the multi-touch sensor, a receive channel that receives a sense signal resulting from the driving of the multi-touch sensor, a receive oscillator, and a demodulation section that demodulates the received sense signal based on a frequency of the receive oscillator to obtain sensing results, the demodulation section including a demodulator and a vector operator.

Claims

1. An integrated multi-touch controller comprising:

drive circuitry configured to be coupled to drive lines of a touch sensor panel and capable of applying a plurality of stimulation signals simultaneously to a plurality of the drive lines;

receive circuitry configured to be coupled to sense lines of the touch sensor panel and capable of receiving sense signals generated in response to the plurality of stimulation signals; and

processing circuitry coupled to the receive circuitry, the processing circuitry comprising;

a demodulator capable of obtaining first capacitance measurements from the sense signals; and

a decoder capable of obtaining second capacitance measurements corresponding to sensing nodes from the first capacitance measurements.

2. The integrated multi-touch controller of claim 1, wherein the drive circuitry comprises a transmit oscillator, wherein the plurality of stimulation signals are generated by the drive circuitry based on a frequency of the transmit oscillator.

3. The integrated multi-touch controller of claim 2, wherein the drive circuitry further comprises:

transmit logic capable of generating one or more digital signals from signals received from the transmit oscillator;

one or more digital-to-analog converters (DACs), the one or more DACs capable of receiving the one or more digital signals from the transmit logic and generating one or more analog signals;

a bus capable of receiving the one or more analog signals from the one or more DACs; and

switching circuitry connected to the bus and capable of selecting, for each of the plurality of the drive lines, one of a plurality of bus signals for transmission to the drive lines, wherein the plurality of bus signals includes the one or more analog signals from the one or more DACs.

4. The integrated multi-touch controller of claim 3, wherein the drive circuitry further comprises:

a plurality of analog output buffers connected to the switching circuitry configured to buffer, for each of the plurality of the drive lines, the one of the plurality of bus signals selected by the switching circuitry for transmission to the touch sensor panel as one of the plurality of stimulation signals.

5. The integrated multi-touch controller of claim 3, wherein the plurality of bus signals includes a first signal having a first frequency matching a frequency of the transmit oscillator and a first phase, and a second stimulation signal having second frequency matching the frequency of the transmit oscillator and a second phase, the second phase different than the first phase.

6. The integrated multi-touch controller of claim 3, wherein the plurality of bus signals include at least one common voltage signal, the common voltage signal comprising a direct current (DC) signal or a ground (GND).

7. The integrated multi-touch controller of claim 3, wherein the one or more DACs consist of a single DAC, the single DAC capable of outputting two alternating current (AC) signals at a common frequency and with a 180°

phase difference.

8. The integrated multi-touch controller of claim 1, further comprising a first memory, wherein the first memory stores parameters specifying which of the plurality of stimulation signals the drive circuitry applies to the plurality of the drive lines during a touch-sensing scan of the touch sensor panel.

9. The integrated multi-touch controller of claim 1, wherein the receive circuitry comprises a plurality of sense channels, each sense channel including:

a charge amplifier;

a filter; and

an analog-to-digital converter (ADC).

10. The integrated multi-touch controller of claim 9, wherein the receive circuitry further comprises offset compensation circuitry capable of subtracting a charge offset from the sense signals.

11. The integrated multi-touch controller of claim 1, wherein the demodulator comprises a plurality of mixers configured to mix each of the sense signals with a demodulation signal to obtain the first capacitance measurements.

12. The integrated multi-touch controller of claim 1, wherein obtaining the second capacitance measurements corresponding to the sensing nodes from the first capacitance measurements comprises decoding the first capacitance measurements based on a plurality of parameters used to generate the plurality of stimulation signals.

13. The integrated multi-touch controller of claim 12, wherein decoding the first capacitance measurements is based on a second plurality of parameters, the second plurality of parameters based on an inverse of the plurality of parameters used to generate the plurality of stimulation signals.

14. The integrated multi-touch controller of claim 13, wherein the second plurality of parameters includes adjustments to compensate for differences in phase delays among the sensing nodes corresponding to the second capacitance measurements.

15. The integrated multi-touch controller of claim 11, the processing circuitry further comprising:

a receive oscillator configured to output the demodulation signal to the demodulator.

16. The integrated multi-touch controller of claim 15, wherein the receive oscillator forms the demodulation signal by generating a periodic waveform and mixing the periodic waveform with an envelope waveform.

17. The integrated multi-touch controller of claim 11, wherein the demodulator is further capable of applying a programmable delay to each of the sense signals to match a phase of the demodulation signal.

18. The integrated multi-touch controller of claim 11, wherein the demodulator further comprises a plurality of integrators, wherein each integrator is capable of integrating an output from one of the plurality of mixers to obtain the first capacitance measurements.

19. The integrated multi-touch controller of claim 1, further comprising one or more memory circuits, wherein the first capacitance measurements and the second capacitance measurements are stored in the one or more memory circuits.

20. The integrated multi-touch controller of claim 1, wherein demodulating and decoding the sense signals are performed using digital signals.