SAR ADC WITH DYNAMIC INPUT SCALING AND OFFSET ADJUSTMENT

• US 20110273402A1
• Filed: 07/20/2011
• Published: 11/10/2011
• Est. Priority Date: 03/27/2008
• Status: Active Grant

• Current Assignee: Christoph Horst Krah, Steve Porter Hotelling
• Original Assignee: Christoph Horst Krah, Steve Porter Hotelling
• Inventors: KRAH, Christoph Horst, HOTELLING, Steve Porter
• Granted Patent: US 9,013,442 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/05 Digital input using the sampling of an analogue quantity at regular intervals of time , input from a/d converter or output to d/a converter

Abstract

An apparatus for generating an image of touch on or about a touch-sensitive surface comprising a touch panel is disclosed. The touch panel can include a plurality of touch sensors configured for detecting one or more touch events occurring at distinct locations at about the same time. Each touch event can comprise a touching of an object against the touch-sensitive surface. A plurality of receive channels can be coupled to the touch panel for generating values representative of detected touch events. The receive channels can include a charge redistribution successive approximation register digital-to-analog converter (SAR ADC) configured to convert an analog waveform into a digital representation via a binary search and outputting the digital representation to an output register. The SAR ADC architecture can be such that it the dynamic input range can be scaled and offset adjusted.

Claims

1. An apparatus for detecting touch events, comprising:

one or more receive channels couplable to one or more touch sensors, the one or more receive channels configurable for generating distinct values representative of the touch events by converting inputted analog waveforms into respective digital representations using a binary search;

wherein at least one receive channel includes a charge redistribution successive approximation register (SAR) analog to digital converter (ADC); and

wherein at least one charge redistribution SAR ADC includes one or more scaling capacitors configurable for scaling a dynamic input range of the SAR ADC.

2. The apparatus of claim 1, wherein at least one of the charge redistribution SAR ADCs comprise a first capacitor and a second capacitor, the first and second capacitors configurable for i) scaling the dynamic input range of the SAR ADC;

and ii) offsetting the dynamic input range by shifting the dynamic input range relative to a reference voltage.

3. The apparatus of claim 2, wherein the first and second capacitors are adjustable.

4. The apparatus of claim 3, wherein scaling of the dynamic input range is a function of a sum of capacitance values of the first capacitor and the second capacitor.

5. The apparatus of claim 3, wherein the offset is a function of a ratio of capacitance values of the first capacitor and the second capacitor.

6. The apparatus of claim 1, further comprising a computing system that incorporates the apparatus, the computing system comprising:

a touch surface including the one or more touch sensors;

a touch subsystem couplable to the one or more touch sensors;

a touch panel processor coupled to the touch system; and

a host processor coupled to the touch panel processor.

7. The apparatus of claim 6, further comprising a mobile telephone that incorporates the computing system.

8. The apparatus of claim 6, further comprising a personal computer that incorporates the computing system.

9. The apparatus of claim 6, further comprising a trackpad that includes the touch surface.

10. The apparatus of claim 6, further comprising a display screen that includes the touch surface.

11. The apparatus of claim 1, wherein the one or more receive channels are configurable for generating distinct values of multiple touch events occurring at distinct locations on or near a touch surface at about the same time.

12. An apparatus for detecting touch events, comprising:

one or more receive channels couplable to one or more touch sensors, the one or more receive channels configurable for generating distinct values representative of the touch events by converting inputted analog waveforms into respective digital representations using a binary search;

wherein at least one receive channel includes a charge redistribution successive approximation register (SAR) analog to digital converter (ADC); and

wherein at least one of the charge redistribution SAR ADCs comprise a first capacitor and a second capacitor, the first and second capacitors configurable for i) scaling the dynamic input range of the SAR ADC; and

ii) offsetting the dynamic input range by shifting the dynamic input range relative to a reference voltage.

13. The apparatus of claim 12, wherein at least one charge redistribution SAR ADC includes one or more scaling capacitors configurable for scaling a dynamic input range of the SAR ADC.

14. The apparatus of claim 12, wherein the first and second capacitors are adjustable.

15. The apparatus of claim 14, wherein scaling of the dynamic input range is a function of a sum of capacitance values of the first capacitor and the second capacitor.

16. The apparatus of claim 14, wherein the offset is a function of a ratio of capacitance values of the first capacitor and the second capacitor.

17. The apparatus of claim 12, further comprising a computing system that incorporates the apparatus, the computing system comprising:

a touch surface including the one or more touch sensors;

a touch subsystem couplable to the one or more touch sensors;

a touch panel processor coupled to the touch system; and

a host processor coupled to the touch panel processor.

18. The apparatus of claim 17, further comprising a mobile telephone that incorporates the computing system.

19. The apparatus of claim 17, further comprising a personal computer that incorporates the computing system.

20. The apparatus of claim 17, further comprising a trackpad that includes the touch surface.

21. The apparatus of claim 17, further comprising a display screen that includes the touch surface.

22. The apparatus of claim 12, wherein the one or more receive channels are configurable for generating distinct values of multiple touch events occurring at distinct locations on or near a touch surface at about the same time.

23. A touch subsystem for detecting touch events on or about a touch-sensitive surface and generating an image of touch, comprising:

driver logic configured for generating an input stimulus;

channel scan logic configured for controlling the driver logic to scan one or more rows of touch sensors in a touch panel by driving the one or more rows with the input stimulus; and

one or more receive channels, each receive channel couplable to a column of touch sensors in the touch pane, at least one receive channel comprising a charge redistribution successive approximation register (SAR) analog to digital converter (ADC) configured for receiving a signal representative of a touch event occurring at one of the touch sensors in the column of touch sensors and generating a digital value representative of the touch event via a binary search,

wherein at least one charge redistribution SAR ADC includes one or more scaling capacitors configurable for scaling a dynamic input range of the SAR ADC.

24. A method for detecting touch events on or about a touch-sensitive surface, comprising:

scanning a touch panel of touch sensors organized in rows and columns by sequentially applying a first stimulus to each row; and

during each touch panel row scan, coupling the columns of the touch panel to one or more receive channels and generating one or more digital values representative of one or more touch events occurring at distinct locations along the row at about the same time;

wherein generating the one or more digital values comprises converting an analog waveform into a digital representation via a binary search implemented by a charge redistribution successive approximation register (SAR) analog to digital converter (ADC); and

wherein at least one charge redistribution SAR ADC includes one or more scaling capacitors configurable for scaling a dynamic input range of the SAR ADC.

25. The method of claim 24, further comprising:

(i) scaling the dynamic input range of the charge redistribution SAR ADC and (ii) offsetting the input range of the charge redistribution SAR ADC.