A capacitive touch sensor providing an automatic switch-off function for
`
`an apparatus in which the sensor is incorporated is provided. The sensor
`
`comprises a sensing element coupled to a capacitance measurement circuit for
`
`measuring the capacitance of the sensing element. A control circuit is operable
`
`to determine from the capacitance measurement whether an objectis in
`
`proximity with the sensor. The determined presence of an object may be used
`
`to toggle a function of the apparatus. Furthermore, when it is determined that
`
`an object has not been in proximity with the sensor for a predetermined time
`
`duration, an output signal for switching off the apparatus is provided. The
`
`predetermined time duration may be selected from a number of predefined
`
`time durations, or may be programmed using an resistor-capacitor network.
`
`Pulses may be applied to the control circuit to override features of the
`
`automatic switch-off functionality.
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page | of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 1 of 54
`
`

`

`BACKGROUND ART
`
`[0001]
`
`This invention relates to proximity sensors. In particular, the invention
`
`relates to capacitive sensors for sensing the presence or touch of an object
`
`adjacent to a sensor.
`
`[0002] Capacitive position sensors have recently become increasingly
`
`common and accepted in humaninterfaces and for machine control. For
`
`example, in the fields of portable media players it is now quite common to find
`
`capacitive touch controls operable through glass or plastic panels. Some mobile
`
`(cellular) telephones are also starting to implement these kinds of interfaces.
`
`[0003] Many capacitive touch controls incorporated into consumer electronic
`
`devices for appliances provide audio and/or visual feedback to a user indicating
`
`whether a finger or other pointing object is present or approaches such touch
`
`controls. A capacitive sensing microprocessor may typically be comprised in
`
`touch-controlled devices which are arranged to provide an “on” output signal
`
`when a finger is adjacent to a sensor and an “off’ output signal when a finger is
`
`not adjacent to a sensor. The signals are sent to a device controller to
`
`implement a required function dependent on whether a user’s finger is in
`
`proximity with or touching an associated touch control.
`
`[0004]
`
`Some touch-controlled devices remain “on” or “active” despite the user
`
`having moved away from the device or a particular function no longer being
`
`required. This results in the device consuming a large amount of power which is
`
`not efficient.
`
`[0005] There is therefore a need for an improved capacitive touch sensor
`
`which can regulate power usage.
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 2 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 2 of 54
`
`

`

`SUMMARYOF THE INVENTION
`
`[0006] According to a first aspect of the invention there is provided a sensor
`
`for determining the presence of an object comprising: a sensing element; a
`
`capacitance measurement circuit operable to measure the capacitance of the
`
`sensing element; and a control circuit operable to determine whether an object
`
`is in proximity with the sensor based on a measurement of the capacitance of
`
`the sensing element, the control circuit further being operable to provide an
`
`output signal to control a function of an apparatus when it is determined that
`
`an object has not been in proximity with the sensor for a predetermined time
`
`duration.
`
`[0007]
`
`The control circuit may be configured so that the predetermined time
`
`duration is selectable from a number of different predefined time durations.
`
`[0008] The control circuit may include a time input terminal and the
`
`predetermined time duration may selectable from the number ofdifferent
`
`predefined time durations according to a voltage applied to the time input
`
`terminal.
`
`[0009]
`
`The control circuit may include a delay multiplier terminal and be
`
`configured so that a selected one of the number of different predefined time
`
`durations is multiplied by a multiplication factor according to a voltage applied
`
`to the delay multiplier terminal so as to provide the predetermined time
`
`duration.
`
`[0010]
`
`The control circuit may be configured so that the predetermined time
`
`duration is programmable by a user to provide a user-selected time duration.
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 3 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 3 of 54
`
`

`

`[0011]
`
`The sensor may comprise a resistor-capacitor (RC) network coupled to
`
`the control circuit and the predetermined time duration may depend on atime
`
`constant of the RC network.
`
`[0012]
`
`The control circuit may include a delay multiplier terminal and be
`
`configured so that the user-selected time duration is multiplied by a
`
`multiplication factor according to a voltage applied to the delay multiplier
`
`terminal to provide the predetermined time duration.
`
`[0013]
`
`The control circuit may be configured such that the provision of the
`
`output signal to control a function of an apparatus after the predetermined
`
`time duration may be overridden so the output signal is not provided when it is
`
`determined that an object has not been in proximity with the sensor fora
`
`predetermined time duration. For example, the control circuit may be operable
`
`to receive an override pulse and on receipt of the override pulse to retrigger the
`
`predetermined time duration to so as to extend the time before the output
`
`signal to control a function of an apparatus is provided.
`
`[0014]
`
`The control circuit may be configured such that the provision of the
`
`output signal to control a function of an apparatus after the predetermined
`
`time duration may be overridden so the output signal is provided beforeit is
`
`determined that an object has not been in proximity with the sensor for a
`
`predetermined time duration. For example, the control circuit may be operable
`
`to receive an override pulse and on receipt of the override pulse to provide the
`
`output signal to control a function of an apparatus.
`
`[0015] The sensor may be configured to perform a recalibration when the
`
`sensor is powered up, when an object is determined to be in proximity with the
`
`sensor for more than a timer setting, and / or when an override is released.
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 4 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 4 of 54
`
`

`

`[0016]
`
`The control circuit may be configured such that the output signalis
`
`toggled between a high state and a low state when an object is determined to
`
`be in proximity with the sensor.
`
`[0017]
`
`The function of an apparatus controlled by the output signal may be a
`
`switch-off function.
`
`[0018]
`
`The capacitance measurement circuit may employ bursts of charge-
`
`transfer cycles to acquire measurements.
`
`[0019] The capacitance measurementcircuit may be configured to operate in
`
`one of more than one acquisition modes depending on the output signal, for
`
`example a low-power mode or a fast mode.
`
`[0020] The capacitance measurementcircuit and the control circuit may be
`
`comprised in a general purpose microcontroller under firmware control.
`
`[0021]
`
`The capacitance measurement circuit and the control circuit may be
`
`comprised within a six-pin integrated circuit chip package, such as an SOT23-6.
`
`[0022] According to a second aspect of the invention there is provided
`
`apparatus comprising a sensor according to the first aspect of the invention.
`
`[0023] According to a third aspect of the invention there is provided a method
`
`for controlling a function of an apparatus comprising: determining whether an
`
`object is in proximity with a sensor based on a measurement of the capacitance
`
`of a sensing element and providing an output signal to control the function of
`
`the apparatus when it is determined that an object has not been in proximity
`
`with the sensor for a predetermined time duration.
`
`[0024] The function of the apparatus controlled by the output signal may be a
`
`switch-off function.
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 5 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 5 of 54
`
`

`

`[0025] According to another aspect of the present invention, there is
`
`provided a sensor for determining the presence of an object comprising: a
`
`sensing element, a capacitance measurement circuit operable to measure the
`
`capacitance of the sensing element, and a control circuit operable to determine
`
`whether an object is in proximity with the sensor based on a measurement of
`
`the capacitance of the sensing element, the control circuit also being operable
`
`to provide an output signal to control a function of an apparatus based on an
`
`object not being in proximity with the sensor and the output signal being
`
`produced after a predetermined time duration.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0026]
`
`For a better understanding of the invention and to show how the same
`
`may be carried into effect reference is now made by way of example to the
`
`accompanying drawings in which:
`
`[0027]
`
`Figure 1 schematically shows sense electrode connections for an
`
`example chip for implementing an auto-off function according to an
`
`embodiment of the invention;
`
`[0028]
`
`Figure 2 schematically represent an application of drift compensation
`
`in the chip of Figure 1;
`
`[0029]
`
`Figure 3 schematically showsa basic circuit configuration for
`
`providing a 15 minute auto switch-off function in an active high output
`
`implementation of an embodiment of the invention;
`
`[0030]
`
`Figure 4 schematically showsa series of fast mode bursts on the SNSK
`
`pin of the chip shown in Figure 1 when in an on condition;
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 6 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 6 of 54
`
`

`

`[0031]
`
`Figure 5 schematically shows a series of low-power mode bursts anda
`
`switch to fast mode power bursts on the SNSK pin of the chip shownin Figure 1
`
`when switching from an off condition to an on condition;
`
`[0032]
`
`Figure 6 schematically shows use of an output configuration resistor
`
`Rop to configure the chip of Figure 1 to have an active high or an active low
`
`output;
`
`[0033]
`
`Figure 7 schematically shows an example circuit configuration for the
`
`chip shown in Figure 1 with the output connected to a digital transistor;
`
`[0034]
`
`Figure 8 schematically shows an example circuit configuration for the
`
`chip shown in Figure 1 configured to provide a predefined auto-off delay;
`
`[0035]
`
`Figure 9 schematically shows an example circuit configuration for the
`
`chip shown in Figure 1 configured to provide a programmable auto-off delay;
`
`[0036]
`
`Figure 10 schematically shows an example pulse applied to the chip
`
`shownin Figure 1 to override an auto-off delay;
`
`[0037]
`
`Figure 11 schematically shows another example pulse applied to the
`
`chip shownin Figure 1 to override an auto-off delay;
`
`[0038]
`
`Figure 12 schematically shows example voltage levels for the chip
`
`shownin Figure 1
`
`in overriding of an auto-off delay;
`
`[0039]
`
`Figures 13 and 14 schematically show typical values of RC divisor K as
`
`a function of supply voltage VDD for the chip shownin Figure 1 with active high
`
`output and active low output respectively;
`
`[0040]
`
`Figure 15 schematically showstypical curves of auto-off delay as a
`
`function of timing resistor value for different capacitor values and different
`
`supply voltages for an active high output configuration;
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 7 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 7 of 54
`
`

`

`[0041]
`
`Figure 16 schematically showstypical curves of auto-off delay as a
`
`function of timing resistor value for different capacitor values and different
`
`supply voltages for an active low output configuration;
`
`[0042]
`
`Figure 17 schematically shows an example application of the chip
`
`shownin Figure 1
`
`in an active low output configuration driving a PNP transistor
`
`with an auto-off time of 3.33 hours;
`
`[0043]
`
`Figure 18 schematically shows another example application of the
`
`chip shown in Figure 1
`
`in an active high output configuration driving a high
`
`impedance with an auto-off time of 135 seconds;
`
`[0044]
`
`Figure 19 schematically shows an implementation of the chip shownin
`
`Figure 1
`
`in an SOT23-6 package; and
`
`[0045]
`
`Figure 20 schematically shows a pin diagram for an implementation of
`
`the chip shownin Figure 1
`
`in an SOT23-6 package.
`
`DETAILED DESCRIPTION
`
`[0046]
`
`In one example, an embodiment of the invention may be implemented
`
`in an integrated circuit chip providing a proximity sensor function. The
`
`integrated circuit chip may thus be incorporated into a device or apparatus to
`
`provide and control a proximity sensor functionality for the device / apparatus
`
`in accordance with an embodiment of the invention. For the purposes of
`
`explanation, a specific integrated circuit chip providing the functionality of an
`
`embodiment of the invention will be described further below. The chip will in
`
`places be referred to by product name QT102. However, it will be appreciated
`
`that the QT102 chip is merely a specific example application of an embodiment
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 8 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 8 of 54
`
`

`

`of the invention. Other embodiments of the invention need not be implemented
`
`in a chip in this way, and furthermore, other embodiments of the invention may
`
`be provided in conjunction with all, some or none of the additional features of
`
`the QT102 chip described further below.
`
`[0047] Before turning specifically to the QT102 chip embodiment, a summary
`
`is provided.
`
`[0048]
`
`It is known that a touch sensitive sensor may comprise a sensor
`
`element, such as an etched copper electrode mounted on a PCB substrate, and
`
`a control circuit for measuring a capacitance of the sensor element to a system
`
`reference potential. The sensor element may be referred to as a sense
`
`electrode. The capacitance of the sense electrode is affected by the presence of
`
`nearby objects, such as a pointing finger. Thus the measured capacitance of the
`
`sense electrode, and in particular changes in the measured capacitance, may be
`
`used to identify the presence of an object adjacent the sense electrode. The
`
`control circuit may be configured to provide an output signal, e.g. by setting an
`
`output logic level as high or low, indicating whether or not an object is deemed
`
`to be adjacent the sense electrode. A controller of a device in which the touch
`
`sensitive sensor is implemented mayreceive the output signal and act
`
`accordingly.
`
`[0049] There are various known technologies for measuring capacitance of a
`
`sense electrode in a capacitive touch sensor. Embodiments of the present
`
`invention may be implemented in conjunction with any of these technologies /
`
`measurement circuits. For example, the fundamental principles underlying the
`
`capacitive sensors described in US 5,730,165, US 6,466,036 and US 6,452,514
`
`could be used.
`
`[0050]_In accordance with embodiments of the invention, the control circuit
`
`of the sensor can determine whether an object or a user’s finger is no longer in
`
`proximity with the sensor and based on a pre-determined time duration, the
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 9 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 9 of 54
`
`

`

`control circuit can produce an output signal automatically to prevent the
`
`capacitance measurement circuit from continually measuring changes in
`
`capacitance due to, for example, the perceived presence of an object in
`
`proximity with the sensor.
`
`[0051] Therefore, the control circuit is able to deactivate, turn-off, or power
`
`down the capacitance measurement circuit where an apparatus has
`
`inadvertently been left on or with the erroneous perception that a user is still
`
`present. This may, for example, be referred to as an “auto-off” feature. The
`
`signal for preventing the capacitance measurementcircuit from continually
`
`measuring changes in capacitance may be referred to as an auto-off signal. The
`
`capacitance measurement circuit and the auto-off control circuit may be
`
`comprised in a general-purpose microcontroller under firmware control, for
`
`example, such as the QT102 chip described further below.
`
`[0052] As described in Section 3.5 of the below numbered sections, and in
`
`conjunction with the drawings, the control circuit of the sensor may be
`
`implemented by different methods — for example, the auto-off signal output
`
`may be produced automatically after different pre-determined time durations to
`
`effect powering downthe capacitance measurement circuit due to no presence
`
`of the user; the control circuit may be programmed bya user So that it may
`
`power downan apparatus based on a user-selected time duration; the control
`
`circuit output signals may be overridden, for example, to extend time durations
`
`before an apparatus is turned-off or to immediately turn-off an apparatus when
`
`a user is no longer present.
`
`[0053] The sensor of the invention may be useful in various applications, for
`
`example in kitchen appliances, light switches, headsets, and other electronic
`
`consumer devices. For example, a coffee machine incorporating a sensor of the
`
`invention may be programmed to power-downafter a time period of, say, 30
`
`minutes, where the coffee machine has been left on inadvertently. This will
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 10 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 10 of 54
`
`

`

`beneficially conserve energy use and minimise the possibility of damage and/or
`
`accidents caused by the coffee machine or glass container(s) overheating.
`
`[0054] Aspects of the QT102 chip referred to above, and which incorporates
`
`an embodimentof the invention, will now be described in the following
`
`numbered sections.
`
`[0055] The numbered sections may be considered to relate generally to
`
`features of the QT102 chip as follows: Section 1
`
`- Overview (including 1.1
`
`Introduction, 1.2 Electrode Drive, 1.3 Sensitivity, 1.3.1 Introduction, 1.3.2
`
`Increasing Sensitivity, 1.3.3 Decreasing Sensitivity, 1.4 Recalibration Timeout ,
`
`1.5 Forced Sensor Recalibration, 1.6 Drift Compensation, 1.7 Response Time,
`
`1.8 Spread Spectrum). Section 2 -Wiring and Parts (including 2.1 Application
`
`Note, 2.2 Cs Sample Capacitor, 2.3 Rs Resistor, 2.4 Power Supply, PCB Layout,
`
`2.5 Wiring). Section 3 - Operation (including 3.1 Acquisition Modes, 3.1.1
`
`Introduction, 3.1.2 OUT Pin ‘On’ (Fast Mode), 3.1.3 OUT Pin ‘Off ’ (Low Power
`
`Mode), 3.2 Signal Processing, 3.2.1 Detect Integrator, 3.2.2 Detect Threshold,
`
`3.3 Output Polarity Selection, 3.4 Output Drive, 3.5 Auto Off Delay, 3.5.1
`
`Introduction, 3.5.2 Auto Off - Predefined Delay, 3.5.3 Auto Off - User-
`
`programmed Delay, 3.5.4 Auto Off - Overriding the Auto Off Delay, 3.5.5
`
`Configuring the User-programmed Auto-off Delay, 3.6 Examples of Typical
`
`Applications). Section 4 - Specifications (including 4.1 Absolute Maximum
`
`Specifications, 4.2 Recommended Operating Conditions, 4.3 AC Specifications,
`
`4.4 Signal Processing, 4.5 DC Specifications, 4.6 Mechanical Dimensions, 4.7
`
`Moisture Sensitivity Level (MSL)).
`
`] Overview
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 11 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 11 of 54
`
`

`

`1.1 Introduction
`
`[0056] The QT102 is a single key device featuring a touch on / touch off
`
`(toggle) output with a programmable auto switch-off capability.
`
`[0057] The QT102 is a digital burst mode charge-transfer (QT) sensor
`
`designed specifically for touch controls; it includes hardware and signal
`
`processing functions to provide stable sensing under a wide variety of changing
`
`conditions. In examples, low cost, non-critical components are employed for
`
`configuring operation.
`
`[0058] The QT102 employs bursts of charge-transfer cycles to acquire its
`
`signal. Burst mode permits power consumption in the microampere range,
`
`dramatically reduces radio frequency (RF) emissions, lowers susceptibility to
`
`electromagnetic interference (EMI), and yet permits good response time.
`
`Internally the signals are digitally processed to reject impulse noise, using a
`
`‘consensus’ filter which in this example requires four consecutive confirmations
`
`of a detection before the output is activated.
`
`[0059] The QT switches and charge measurement hardware functions areall
`
`internal to the QT102.
`
`1.2 Electrode Drive
`
`[0060]
`
`Figure 1 schematically shows the sense electrode connections (SNS,
`
`SNSK) for the QT102.
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 12 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 12 of 54
`
`

`

`[0061]
`
`For improved noise immunity, it may be helpful if the electrode is only
`
`connected to the SNSK pin.
`
`[0062]
`
`In examples the sample capacitor Cs may be much larger than the
`
`load capacitance (Cx). E.g. typical values for Cx are 5 to 20pF while Cs is usually
`
`1 or 2 to 50nF. (Note: Cx is not a physical discrete component on the PCB, it is
`
`the capacitance of the touch electrode and wiring. It is shown in Figure 1 to aid
`
`understanding of the equivalent circuit.)
`
`[0063]
`
`Increasing amounts of Cx destroy gain, therefore it is important to
`
`limit the amount of load capacitance on both SNS terminals. This can be done,
`
`for example, by minimizing trace lengths and widths and keeping these traces
`
`away from power or ground traces or copper pours.
`
`[0064] Thetraces and any components associated with SNS and SNSK will
`
`become touch sensitive and so may need to be considered to help in limiting
`
`the touch-sensitive area to the desired location.
`
`[0065]
`
`A series resistor, Rs, may be placed in line with SNSK to the electrode
`
`to suppress electrostatic discharge (ESD) and Electromagnetic Compatibility
`
`(EMC) effects.
`
`1.3 Sensitivity
`
`1.3.1 Introduction
`
`[0066]
`
`The sensitivity of the QT102 is a function of such things as:
`
`- the value of Cs
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 13 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 13 of 54
`
`

`

`- electrode size and capacitance
`
`- electrode shape and orientation
`
`- the composition and aspect of the object to be sensed
`
`- the thickness and composition of any overlaying panel material
`
`- the degree of ground coupling of both sensor and object
`
`1.3.2 Increasing Sensitivity
`
`[0067]
`
`In some cases it may be desirable to increase sensitivity; for example,
`
`when using the sensor with very thick panels having a low dielectric constant.
`
`Sensitivity can often be increased by using a larger electrode or reducing panel
`
`thickness. Increasing electrode size can have diminishing returns, as high
`
`values of Cx will reduce sensor gain.
`
`[0068] The value of Cs also has an effect on sensitivity, and this can be
`
`increased in value with the trade-off of slower response time and more power.
`
`Increasing the electrode's surface area will not substantially increase touch
`
`sensitivity if its diameter is already significantly larger in surface area than the
`
`object being detected. Panel material can also be changed to one having a
`
`higher dielectric constant, which will better help to propagate the field.
`
`[0069] Ground planes around and under the electrode and its SNSK trace may
`
`lead to high Cx loading and destroy gain. Thus in some cases the possible
`
`signal-to-noise ratio benefits of ground areas may be more than negated by the
`
`decreased gain from the circuit, and so ground areas around electrodes may be
`
`discouraged in some circumstances. Metal areas near the electrode may reduce
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 14 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 14 of 54
`
`

`

`the field strength and increase Cx loading and so it may be helpful if these are
`
`avoided if possible. It may be helpful to keep ground away from the electrodes
`
`and traces.
`
`1.4 Recalibration Timeout
`
`[0070]
`
`If an object or material obstructs the sense electrode the signal may
`
`rise enough to create a detection, preventing further operation. To help reduce
`
`the risk of this, the sensor includes a timer which monitors detections. If a
`
`detection exceeds the timer setting (known as the Max On-duration) the sensor
`
`performs a full recalibration. This does not toggle the output state but ensures
`
`that the QT102 will detect a new touch correctly. The timer is set to activate
`
`this feature after ~ 30 seconds. This will vary slightly with Cs.
`
`1.5 Forced Sensor Recalibration
`
`[0071] The QT102 has no recalibration pin; a forced recalibration is
`
`accomplished when the device is powered up, after the recalibration timeout or
`
`when the auto-off override is released.
`
`[0072] However, supply drain is low so it is a simple matter to treat the entire
`
`IC as acontrollable load; driving the QT102's VDD pin directly from another
`
`logic gate or a microcontroller port will serve as both power and ‘forced
`
`recal(ibration)'. The source resistance of most CMOSgates and microcontrollers
`
`are low enough to provide direct power without problems.
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 15 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 15 of 54
`
`

`

`1.6 Drift Compensation
`
`[0073]
`
`Signal drift can occur because of changes in Cx and Cs over time. It
`
`may be helpful if drift is compensated for, otherwise false detections,
`
`nondetections, and sensitivity shifts may follow.
`
`[0074] Drift compensation is schematically shownin Figure 2. Drift
`
`compensation is performed by making a reference level track the raw signal at a
`
`slow rate, but only while there is no detection in effect. It may be helpful if the
`
`rate of adjustment is performed relatively slowly, otherwise there may be a risk
`
`that legitimate detections may be ignored. The QT102 drift compensates using
`
`a slew-rate limited change to the reference level; the threshold and hysteresis
`
`values are slaved to this reference.
`
`[0075] Once an object is sensed, the drift compensation mechanism ceases
`
`since the signal is legitimately high, and therefore should not cause the
`
`reference level to change (as indicated in Figure 2 during the period between
`
`the vertical dotted lines).
`
`[0076] The QT102's drift compensation is ‘asymmetric’; the reference level
`
`drift-compensates in one direction faster than it does in the other. Specifically,
`
`it compensates faster for decreasing signals than for increasing signals. It may
`
`be helpful if increasing signals are not compensated for quickly, since an
`
`approaching finger could be compensatedfor partially or entirely before
`
`approaching the sense electrode.
`
`[0077] However, an obstruction over the sense pad, for which the sensor has
`
`already made full allowance, could suddenly be removed leaving the sensor
`
`with an artificially elevated reference level and thus become insensitive to
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 16 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 16 of 54
`
`

`

`touch. In this latter case, the sensor will compensate for the object's removal
`
`more quickly, for example in only a few seconds.
`
`[0078] With relatively large values of Cs and small values of Cx, drift
`
`compensation will appear to operate more slowly than with the converse. Note
`
`that the positive and negative drift compensation rates are different.
`
`1.7 Response Time
`
`[0079] The QT102's response time is dependent on burst length, which in
`
`turn is dependent on Cs and Cx. With increasing Cs, response time slows, while
`
`increasing levels of Cx reduce response time.
`
`1.8 Spread Spectrum
`
`[0080] The QT102 modulates its internal oscillator by +7.5 percent during the
`
`measurement burst. This spreads the generated noise over a wider band
`
`reducing emission levels. This also reduces susceptibility since there is no
`
`longer a single fundamental burst frequency.
`
`2 Wiring and Parts
`
`[0081]
`
`Figure 3 schematically showsa basic circuit configuration for an
`
`implementation of an embodiment of the invention.
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 17 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 17 of 54
`
`

`

`2.1 Application Note
`
`[0082] Although not directly relevant for embodiments of the invention, for
`
`completeness, reference may be made to Application Note AN-KDO2 (“Secrets of
`
`a Successful QTouch (TM) Design), included herein in its entirety by reference,
`
`and downloadable from the Quantum Research Group website, for information
`
`on example construction and design methods. Go to http://www.qprox.com,
`
`click the Support tab and then Application Notes.
`
`2.2 Cs Sample Capacitor
`
`[0083]
`
`Cs is the charge sensing sample capacitor. The required Cs value
`
`depends on the thickness of the panel and its dielectric constant. Thicker
`
`panels require larger values of Cs. Typical values are 1 or 2 nF to 50nF
`
`depending on the sensitivity required; larger values of Cs may demand higher
`
`stability and better dielectric to ensure reliable sensing.
`
`[0084] The Cs capacitor may be a stable type, such as X7R ceramic or PPS
`
`film. For more consistent sensing from unit to unit, 5 percent tolerance
`
`capacitors are recommended. X7R ceramic types can be obtained in 5 percent
`
`tolerance for little or no extra cost. In applications where high sensitivity (long
`
`burst length) is required, the use of PPS capacitors is recommended.
`
`2.3 Rs Resistor
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 18 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 18 of 54
`
`

`

`[0085]
`
`Series resistor Rs is in line with the electrode connection and may be
`
`used to limit electrostatic discharge (ESD) currents and to suppress radio
`
`frequency interference (RFI). It may be approximately 4.7kQ to 33kQ, for
`
`example.
`
`[0086] Although this resistor may be omitted, the device may become
`
`susceptible to external noise or RFI. For more details of how to select these
`
`resistors see the Application Note AN-KDO2 referred to abovein Section 2.1.
`
`2.4 Power Supply, PCB Layout
`
`[0087] The power supply (between VDD and VSS / system ground) can range
`
`between 2.0V and 5.5V for the QT102 implementation. If the power supply is
`
`shared with another electronic system, it may be helpful if care is taken to
`
`ensure that the supplyis free of digital spikes, sags, and surges which can
`
`adversely affect the device. The QT102 will track slow changes in VDD, but it
`
`may be more affected by rapid voltage fluctuations. Thus it may be helpful if a
`
`separate voltage regulator is used just for the QT102 to isolate it from power
`
`supply shifts caused by other components.
`
`[0088]_If desired, the supply can be regulated using a Low Dropout (LDO)
`
`regulator. See Application Note AN-KDO2 (see Section 2.1) for further
`
`information on power supply considerations.
`
`[0089]
`
`Suggested regulator manufacturers include:
`
`Toko (XC6215 series)
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 19 of 54
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1020, IPR2021-01161
`Page 19 of 54
`
`

`

`Seiko (S817 series)
`
`BCDSemi (AP2121 series)
`
`[0090]
`
`Parts placement: The chip may be placed to minimize the SNSK trace
`
`length to reduce low frequency pickup, and to reduce Cx which degrades gain.
`
`It may be helpful if the Cs and Rsresistors (see Figure 3) are placed close to the
`
`body of the chip so that the trace between Rs and the SNSK pin is relatively
`
`short, thereby reducing the antenna-like ability of this trace to pick up high
`
`frequency signals and feed them directly into the chip. A ground plane can be
`
`used under the chip and the associated discretes, but it may be helpful if the
`
`trace from the Rsresistor and the electrode do not run near ground, to reduce
`
`loading.
`
`[0091]
`
`For improved Electromagnetic compatibility (EMC) performance the
`
`circuit may be made entirely with surface mount technology (SMT) components.
`
`[0092]
`
`Electrode trace routing: It may be helpful to keep the electrode trace
`
`(and the electrode itself) away from other signal, power, and ground traces
`
`including over or next to ground planes. Adjacent switching signals can induce
`
`noise onto the sensing signal; any adjacent trace or ground plane next to, or
`
`under, the electrode trace will cause an increase in Cx load and desensitize the
`
`device.
`
`[0093] Note: a 100nF (0.1 uF) ceramic bypass capacitor (not shownin Figure
`