PATENT DOCUMENT

Publication Number: US-10295612-B2
Application Number: US-201615332119-A
Country: US
Kind Code: B2

Title: Electronic device with resistive sensor array

Abstract:
An array of resistive sensor circuits may be used to gather sensor data. Each resistive sensor circuit may have a resistive sensor and an associated switch. Row decoder circuitry may supply rows of the sensor circuits with control signals on row lines. Capacitors associated with respective columns of the array may be provided with an initialization voltage. The control signals on the row lines may be used to turn on the switches in a selected row of the resistive sensor circuits and thereby discharge the capacitors through the resistive sensors of that row. Comparators may have first inputs coupled to the capacitors and second inputs that receive a reference voltage. A column readout circuit may have memory and processing circuitry that receives count values from a counter and that stores the count values in response to toggling output signals from the comparators.

Claims:
What is claimed is: 
     
       1. Resistive sensor circuitry, comprising:
 an array of resistive sensors having rows and columns, wherein the array of resistive sensors are configured to make ambient air measurements; and 
 resistive sensor array control circuitry including row decoder circuitry that is configured to select a row of the array and column readout circuitry that gathers resistive sensor measurements from each of the resistive sensors in the selected row, wherein the column readout circuitry further comprises:
 memory cells, each of which is coupled to a respective column of resistive sensors in the array; and 
 a counter that provides the memory cells with a count value. 
 
 
     
     
       2. The resistive sensor circuitry defined in  claim 1  wherein the column readout circuitry includes capacitors and wherein each of the capacitors discharges through a respective one of the resistive sensors in the selected row. 
     
     
       3. The resistive sensor circuitry defined in  claim 2  wherein the column readout circuitry includes comparators. 
     
     
       4. The resistive sensor circuitry defined in  claim 3  wherein each column of the array has an associated column line and wherein each of the capacitors discharges through a respective one of the resistive sensors in the selected row through a respective one of the column lines. 
     
     
       5. The resistive sensor circuitry defined in  claim 1 , wherein each of the memory cells receives a comparator output signal from a respective one of the comparators and is configured to store the count value when that comparator output signal toggles. 
     
     
       6. The resistive sensor circuitry defined in  claim 5  wherein the column readout circuitry further comprises:
 a first digital-to-analog converter that produces an initialization voltage; and 
 a second digital-to-analog converter that produces a reference voltage for the comparators, wherein each of the resistive sensors comprises a resistive sensor selected from the group consisting of: a pressure sensor, a gas sensor, a magnetic sensor, a force sensor, an acoustic sensor, a temperature sensor, a humidity sensor, and a particulate sensor. 
 
     
     
       7. The resistive sensor circuitry defined in  claim 6  further comprising:
 first switching circuitry coupled between the resistive sensors and the column lines, wherein the capacitors discharge through the resistive sensors in the selected row by discharging through the column lines, the first switching circuitry, and the resistive sensors; and 
 second switching circuitry coupled between the first digital-to-analog converter circuitry and the capacitors that is configured to supply the capacitors with the initialization voltage before the capacitors are discharged through the resistive sensors. 
 
     
     
       8. Circuitry, comprising:
 an array of resistive sensors having rows and columns, wherein each row includes a row line and wherein each column includes a column line, wherein each resistive sensor in the array is coupled to a respective column line via a corresponding first switch; 
 a row decoder configured to control the first switch associated with each resistive sensor in the array; 
 capacitors, wherein each capacitor is coupled to a respective one of the column lines at a node; and 
 second switches each of which is coupled to a respective one of the nodes. 
 
     
     
       9. The circuitry defined in  claim 8  wherein each of the resistive sensors comprises a resistive sensor selected from the group consisting of: a pressure sensor, a gas sensor, a magnetic sensor, a force sensor, an acoustic sensor, a temperature sensor, a humidity sensor, and a particulate sensor. 
     
     
       10. The circuitry defined in  claim 8  further comprising comparators, each comparator having a first input coupled to a respective one of the nodes, having a second input that receives a reference voltage, and having an output. 
     
     
       11. The circuitry defined in  claim 10  wherein each of the second switches is configured to supply an initialization voltage to the node coupled to that second switch when that second switch is closed. 
     
     
       12. The circuitry defined in  claim 11  further comprising row decoder circuitry that supplies control signals to the first switches through the row lines. 
     
     
       13. The circuitry defined in  claim 12  wherein the row decoder circuitry is configured to turn on the first switches in a selected one of the rows so that the capacitors discharge through the resistive sensors in the selected one of the rows. 
     
     
       14. The circuitry defined in  claim 13  further comprising:
 a counter; and 
 memory and processing circuitry that stores count values from the counter in the memory and processing circuitry in response to signals from the outputs of the comparators. 
 
     
     
       15. Resistive sensor circuitry, comprising:
 an array of resistive sensor circuits having rows and columns, wherein each resistive sensor circuit has a switch and a resistive sensor having a first terminal coupled to the switch and a second terminal directly connected to a ground line; 
 capacitors each of which is associated with one of the columns; and 
 row decoder circuitry that selectively turns on the switches in a selected one of the rows and thereby discharges the capacitor in each column through the resistive sensor that is in the selected row and that is in that column. 
 
     
     
       16. The resistive sensor circuitry defined in  claim 15  wherein each of the resistive sensors comprises a resistive sensor selected from the group consisting of: a pressure sensor, a gas sensor, a magnetic sensor, a force sensor, an acoustic sensor, a temperature sensor, a humidity sensor, a particulate sensor, and a light sensor. 
     
     
       17. The resistive sensor circuitry defined in  claim 16  further comprising at least one heater that heats at least one of the resistive sensors. 
     
     
       18. The resistive sensor circuitry defined in  claim 16  further comprising comparators each of which has a first input coupled to a respective one of the capacitors and each of which has a second input that receives a reference voltage. 
     
     
       19. The resistive sensor circuitry defined in  claim 18  further comprising a circuit that receives count values from a counter and that stores the count values in response to signals from the comparators.

Description:
This application claims the benefit of provisional patent application No. 62/318,546, filed Apr. 5, 2016, which is hereby incorporated herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices and, more particularly, to electronic devices with sensors. 
     BACKGROUND 
     Electronic devices sometimes contain resistive sensors. Resistive sensors may be used, for example, to make magnetic measurements or chemical gas measurements. Sensors such as these have sensor elements that change resistance as a function of exposure to magnetic fields of varying strength or exposure to different concentrations of a gas in the atmosphere. 
     Conventional resistive sensor support circuitry is based on operational amplifier circuitry that converts resistance variations into voltage measurements for digitization by an analog-to-digital converter. This type of arrangement is generally only suitable for single-element resistive sensing applications. 
     SUMMARY 
     An electronic device may have input-output devices such as resistive sensors. An array of resistive sensor circuits may be used to gather sensor data. The array may have rows and columns of the resistive sensor circuits. Each resistive sensor circuit may have a resistive sensor and an associated switch. 
     Resistor sensor array control circuitry may be used to gather resistive sensor data from the array of resistive sensors. The resistor sensor array control circuitry may include row decoder circuitry coupled to row lines and column readout circuitry coupled to column lines. Each row of the array may have an associated one of the row lines and each column of the array may have an associated one of the column lines. 
     The row decoder circuitry may supply rows of the sensor circuits with control signals on the row lines. Capacitors may be provided with an initialization voltage. The control signals on the row lines may be used to turn on the switches in a selected row of the resistive sensor circuits and thereby discharge the capacitors through the resistive sensors of that row. 
     Comparators in the column readout circuitry may have first inputs coupled to the capacitors and second inputs that receive a reference voltage. The column readout circuit may have memory and processing circuitry that receives count values from a counter and that stores the count values in response to toggling output signals from the comparators. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of an illustrative electronic device with sensors in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative resistive sensor in accordance with an embodiment. 
         FIG. 4  is a graph showing signals involved in making resistive sensor measurements in an electronic device in accordance with an embodiment. 
         FIG. 5  is a circuit diagram of circuitry for processing resistive sensor measurements in accordance with an embodiment. 
         FIG. 6  is a graph showing signals involved in processing resistive sensor measurements using circuitry of the type shown in  FIG. 5  in accordance with an embodiment. 
         FIG. 7  is a circuit diagram of circuitry for processing sensor measurements from an array of resistive sensors in accordance with an embodiment. 
         FIG. 8  is a flow chart of illustrative operations involved in gathering resistive sensor data from an array of resistive sensors and taking suitable action in an electronic device in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with sensors. Sensors may be used to measure air pressure, gas composition, magnetic field strength, force, ultrasonic or non-ultrasonic acoustic signals, and/or other parameters. These sensors may have sensor elements that operate based on piezoelectric effects, strain gauge structures, semiconductor structures, microelectromechanical systems (MEMS) structures, sensor structures with interdigitated sets of conductive fingers, and/or other types of sensor elements. Illustrative configurations in which the sensors for the electronic devices exhibit changes in resistance (i.e., configurations in which the sensors are resistive sensors) may sometimes be described herein as an example. 
       FIG. 1  is a perspective view of an illustrative electronic device of the type that may include resistive sensors. Electronic device  10  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, an accessory (e.g., earbuds, a remote control, a wireless trackpad, etc.), or other electronic equipment. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a cellular telephone, media player, tablet computer, wrist-watch device or other portable computing device. Other configurations may be used for device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     In the example of  FIG. 1 , device  10  includes display  14 . Display  14  has been mounted in housing  12 . Electronic device housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch sensor electrodes may be formed from an array of indium tin oxide pads, other transparent conductive structures, or other touch sensor electrode structures. 
     Display  14  may include an array of pixels formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of plasma display pixels, an array of organic light-emitting diode pixels or other light-emitting diode pixels, an array of electrowetting pixels, or pixels based on other display technologies. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass, clear plastic, transparent ceramic, sapphire or other transparent crystalline material, or other transparent layer(s). The display cover layer may have a planar shape, a convex curved profile, a concave curved profile, a shape with planar and curved portions, a layout that includes a planar main area surrounded on one or more edge portions that are bent out of the plane of the planar main area, or other suitable shape. An opening may be formed in the display cover layer to accommodate a speaker port. Openings may also be formed in the display cover layer and/or housing  12  to accommodate buttons  16 . 
     Openings may also be formed in housing  12  to sensor ports such as sensor port  28 . Resistive sensors such as resistive sensor  20  of  FIG. 1  may be mounted within the interior of housing  12  in alignment with sensor port  28  and/or may be mounted elsewhere within device  10 . In some configurations, resistive sensors make measurements on the ambient air surrounding device  10  (e.g., measurements on the chemical composition of the ambient air, humidity, temperature, pressure, etc.). In this type of arrangement, ambient air from the exterior of device  10  may communicate with sensor  20  through port  28 . In other configurations, resistive sensors may be mounted on a printed circuit board or other substrate in the interior of device  10  and may make measurements through the wall of housing  12  or a window structure without using a sensor port opening (e.g., to make magnetic measurements, etc.). 
     Sensor arrays and other groups of multiple resistive sensors may be used to enhance sensor dynamic range and accuracy and may otherwise be used to enhance the ability of the sensors to make desired sensor measurements for device  10  (e.g., to cover additional types of sensor measurement, etc.). The resistive sensors in an array may be formed from a set of sensors that are integrated onto a common substrate (e.g., a common semiconductor die such as a common silicon substrate) or may be formed from discrete sensor substrates. Resistive sensor processing circuitry (e.g., resistive sensor array processing circuitry) may be incorporated on the same substrate as an array of sensors (as an example). 
       FIG. 2  is a schematic diagram of an illustrative electronic device of the type that may be provided with resistive sensors. As shown in  FIG. 2 , electronic device  10  may have control circuitry  22 . Control circuitry  22  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  22  may be used to control the operation of device  10 . For example, the processing circuitry may display alerts, may display sensor measurement data, and may take other suitable actions in response to magnetic field measurements, temperature measurements, ambient air gas composition measurements, ambient air particulate measurements, ambient air relative humidity measurements, etc. The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in device  10  such as input-output devices  24  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  24  may include buttons such as buttons  16  and other buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators or other components with moving parts, cameras, light-emitting diodes and other status indicators, data ports, etc. As shown in  FIG. 2 , input-output devices  24  may include sensors  20 . Sensors  20  may include resistive sensors that make magnetic field measurements, chemical measurements (e.g., ambient air gas composition measurements), ambient air particulate measurements, ambient air relative humidity measurements, temperature measurements, pressure measurements, force (stress) measurements, ambient light measurements and other light measurements, acoustic measurements, touch input measurements, etc. A user can control the operation of device  10  by supplying commands through input-output devices  24  and may receive status information and other output from device  10  using the output resources of input-output devices  24 . Input-output devices  24  may include one or more displays such as display  14 . 
     Control circuitry  22  may be used to run software on device  10  such as operating system code and applications. During operation of device  10 , the software running on control circuitry  22  may display images on display  14  using an array of pixels in display  14 . The software running on control circuitry  22  may gather sensor data from sensors  20  and may display alerts and other information on display  14  based on gathered sensor measurements. 
     A cross-sectional side view of an illustrative resistive sensor is shown in  FIG. 3 . As shown in  FIG. 3 , sensor  20  may include a sensor element such as sensor element  20 A and an associated heating element such as optional heating element  20 B. Heater element  20 B may use ohmic heating, inductive heating, and/or other heating techniques adjust the temperature T of sensor element  20 A. In some sensors, sensor resistivity changes that take place as a function of temperature can be used to help discriminate between different gases (i.e., to identify particular constituent gases such as ozone or carbon dioxide in ambient air). By monitoring the way in which the resistivity of sensor element  20 A changes in response to changes in temperature T, accuracy may be enhanced. 
     In the upper graph of  FIG. 4 , the temperature T that is produced by heaters such as heater  20 B for a pair of sensors  20  has been plotted as a function of time t. As shown in this graph, temperature T may start at ambient temperature T 1  and may be elevated to temperature T 2  before being reduced again to temperature T 1 . The middle graph of  FIG. 4  shows the response (measured resistance RS 1 ) of a first sensor in the pair as a function of time t and the lower graph of  FIG. 4  shows the response (measured resistance RS 2 ) of a second sensor in the pair as a function of time t. In the  FIG. 4  example, both the first and second sensors have been exposed to first and second gases. Trace  30  represents the response of resistance RS 1  for the first sensor when the first sensor is in the presence of the first gas. Trace  32  represents the response of resistance RS 1  for the first sensor when the first sensor is in the presence of the second gas. Trace  34  represents the response of resistance RS 2  for the second sensor when the second sensor is in the presence of the first gas. Trace  36  represents the response of resistance RS 2  for the second sensor when the second sensor is in the presence of the second gas. 
     With one illustrative scenario, the first sensor may be an ozone sensor and the second sensor may be a carbon diode sensor. The first gas may be air containing a high concentration of ozone and the second gas may be air containing a low concentration of ozone. The CO 2  concentration for the first and second air samples may be the same (in this example). As shown in the graphs of  FIG. 4 , the first sensor (i.e., the ozone sensor) exhibits a significant change in resistivity RS 1  when exposed to ozone (and this effect is most pronounced at elevated temperatures). The second sensor (i.e., the carbon dioxide sensor in this example) does not exhibit a significant change in resistivity RS 2 . Using measurements of the resistances RS 1  and RS 2 , control circuitry  22  of device  10  can determine the chemical composition of ambient air. Resistive sensor measurements may also be made to measure ambient air pressure, temperature, humidity, magnetic field strength, force, acoustic levels, strain, and other physical parameters, etc. 
     Sensor dynamic range, sensor accuracy, and sensor coverage (e.g., the number of different types of gases that are monitored, the number of orientations in which magnetic field is measured, the number of different types of physical parameters such as temperature, magnetic field, pressure, etc. that are monitored, etc.) may be enhanced by using an array of resistive sensors. The array may be a rectangular array having rows and columns of resistive sensors. There may, in general, be any suitable number of rows and columns of sensors in the sensor array (e.g., two or more rows and two or more columns, three or more rows and three or more columns, four or more rows and/or columns, five to ten rows and/or columns, fewer than 20 rows and/or columns, etc.). 
     An illustrative circuit of the type that may be used to process resistive sensor measurements for resistive sensors in an array is shown in  FIG. 5 . Circuitry  63  of  FIG. 5  may include resistive sensor circuit  30  and readout circuitry  40 . Resistive sensor circuit  35  may include a resistive sensor such as resistive sensor  37 . Sensor  37  may have a first terminal coupled to ground  33  and a second terminal coupled to node  41 . During operation, the resistance of resistive sensor  37  between the first and second terminals may vary, as described in connection with  FIGS. 3 and 4 . Resistive sensor circuit  35  may also include switching circuitry such as switch  38 . Switch  38  may have a control input that receives a control signal from control circuitry in device  10  via line  43 . 
     Readout circuitry  40  may be used to measure the resistance of resistive sensor  37 . With the illustrative configuration of  FIG. 5 , circuitry  40  produces a logic signal COMPOUT having a duration that is responsive to the size of the resistance of resistive sensor  37 . 
     Circuitry  40  may include digital-to-analog converter  42  and digital-to-analog-converter  64 . Converter  42  may produce a known initialization voltage Vi on line  44 . Switch  46  may have a control input that receives a control signal from control circuitry in device  10  via line  66 . Capacitor  50  may have a first terminal coupled to node  48  and a second terminal coupled to ground  52 . When it is desired to establish a known initialization voltage Vi on node  48  and thereby load voltage Vi onto capacitor  50 , switch  46  may be closed. Switch  46  may then be opened to allow capacitor  50  to discharge through sensor  32  during resistance measurement operations. 
     During resistance measurement operations, digital-to-analog converter  64  may place a known reference voltage Vref on line  56 . Comparator  54  has two inputs. Input  60  may be coupled to line  56  and may receive reference voltage Vref. Input  58  may be coupled to node  48  and may receive a voltage Vout from node  48 . Comparator  54  compares the voltages on inputs  60  and  58  and produces a corresponding output signal (i.e., signal COMPOUT) on output  62  (i.e., a digital signal pulse). The duration of the COMPOUT pulse is reflective of the rate at which capacitor  50  discharges through resistive sensor  37  and can therefore be processed to determine the resistance (sensor reading) from resistive sensor  37 . 
       FIG. 6  is a graph illustrating the operation of circuitry  64  when processing resistive sensor measurements from resistive sensor  37 . 
     At time t 0 , switch  38  is opened to isolate node  48  from resistive sensor  37 . Switch  46  is closed to load known initialization voltage Vi onto node  48  and capacitor  50 . Accordingly, the voltage Vout on node  48  is equal to Vi at time t 0 . Comparator  54  compares the value of Vout to Vref and produces comparator output COMPOUT. Reference voltage Vref is less than initialization voltage Vi, so COMPOUT is high (i.e., a logic one) at time t 0 . 
     After loading Vi onto node  48 , switch  46  is opened and switch  38  is closed. This allows the voltage Vout on capacitor  50  to discharge to ground  33  through switch  38  and resistive sensor  37 . When Vout drops below Vref, the output COMPOUT of comparator  54  will toggle (i.e., COMPOUT will change to a logic zero). 
     Two scenarios are illustrated in the graphs of  FIG. 6 . In the first scenario, the resistance of resistive sensor  37  is relatively high. In the second scenario, the resistance of resistive sensor  37  is relatively low. 
     In the high resistance scenario, capacitor  50  discharges relatively slowly. Voltage Vout starts at Vi (at time t 0 ) and decays to below Vref at time TL, as indicated by trace  70  in the upper graph of  FIG. 6 . As shown by trace  72  in the lower graph of  FIG. 6 , comparator  54  detects that Vout has fallen below Vref at time TL and takes COMPOUT low at time TL. 
     In the low resistance scenario, the resistance of resistive sensor  37  is relatively low. As a result, capacitor  50  discharges more rapidly through sensor  37 , as indicated by trace  74  in the upper graph of  FIG. 6 . At a time TS that is less than time TL, voltage Vout drops below Vref. Comparator  54  therefore takes COMPOUT low at time TS, as indicated by trace  76  in the lower graph of  FIG. 6 . Because the duration (time TL in the higher resistance scenario and time TS in the lower resistance scenario) of the COMPOUT signal following closure of switch  38  (i.e., the duration of COMPOUT while discharging capacitor  50 ) is governed by the resistance of resistive sensor  37 , COMPOUT may be processed by the control circuitry of device  10  to produce a digital signal indicative of the sensor reading of sensor  37 . 
     As shown in  FIG. 7 , device  10  may be provided with an array of resistive sensor circuits  31 . Resistive sensor array  80  may contain any suitable number of circuits  31  (e.g., two or more, four or more, eight or more, 16 or more, 2-20, 4-25, 4-36, fewer than 20, more than 40, etc.). Array  80  may have an equal number of rows and columns, may have unequal numbers of row and columns (i.e., array  80  may be rectangular), or may have other suitable shapes and sizes. Each resistive sensor circuit  31  may have a resistive sensor and associated switch, as shown by resistive sensor  37  and switch  38  of  FIG. 5 . 
     Control circuitry  22  ( FIG. 2 ) may be used to gather sensor measurements from sensor array  80 , may be used to process the sensor measurements, and may be used to take suitable actions based on the sensor measurements. As shown in  FIG. 7 , for example, control circuitry  22  may include resistive sensor array control circuitry  82  that is coupled to array  80  and that supplies array  80  with control signals while gathering sensor data from sensors  37  in array  80 . Resistive sensor array control circuitry  82  may include row decoder circuitry  84  or other circuitry that supplies control signals on row lines  86  to rows of switches  38  in associated rows of sensor circuits  31  of array  80 . Row decoder circuitry  84  may assert a control signal on each row line  86  in sequence while deasserting control signals on all other row lines  86  in array  80 . In this way, row decoder circuitry  84  may activate the switches  38  in array  80  in a row-by-row fashion. If desired, other sensor array readout patterns may be used (e.g., non-sequential row access patterns). 
     As each row of circuits  31  in array  80  is selected, column readout circuitry  90  may be used to sense the resistances of each of the resistive sensors in the selected row. Column readout circuitry  90  may include digital-to-analog converter circuitry  42  for producing initialization voltage Vi and may include digital-to-analog converter circuitry  64  for producing reference voltage Vref. A row of switches  46  in circuitry  90  may be used to supply initialization voltage Vi to nodes  48 . Each of nodes  48  may be coupled to one of the terminals of a respective capacitor in a row of capacitors  50 , as described in connection with switch  46  and capacitor  50  of  FIG. 5 . There may be a capacitor  50  associated with each column of array  80 . Each node  48  and therefore each capacitor  50  may be coupled to a respective column line  88 . Each column line  88  may be coupled to each of the switches  38  of the sensor circuits  31  of a respective column of array  80 . By turning on the switches  38  of a selected row, the resistive sensors  37  of that row may be coupled to the associated row of capacitors  50 . This allows voltages Vout on capacitors  50  to discharge in parallel through the resistive sensors  37  of the selected row. 
     Column readout circuitry  90  may include a row of comparators  54 , each of which is associated with a respective column of resistive sensor circuits  31 . Comparators  54  may supply output signals COMPOUT to memory and processing circuit  92 . Circuitry  92  may have a row of memory cells  94 , each of which is associated with a respective column of array  80 . Circuitry  92  may receive a counter output signal (sometimes referred to as a count value or count) such as signal COUNT from counter  96 . The value of COUNT when COMPOUT toggles in a given column (e.g., when COMPOUT falls from high to low at a time such as time TS or TL in the examples of  FIG. 6 ) may be stored in the memory cell  94  for that column. In this way, a digital value (e.g., a 12 bit count value or other suitable digital count value) that represents the resistance of each resistive sensor  37  in the currently selected row may be gathered by circuit  92 . These resistance values may then be read out of circuit  92  using processing circuitry  98  and suitable action taken (e.g., processing circuitry  98  may display the resistive sensor data from sensors  32 , may issue alerts when sensor data passes predetermined threshold values, may provide applications running on control circuitry  22  with sensor information so that a user of device  10  can be informed about current ambient air conditions, magnetic readings, air pressure information, and/or other resistive sensor data. 
     If desired, circuits  31  of array  80  and circuitry  82  (and, if desired, circuitry  98 ) may be implemented on a common semiconductor substrate (e.g., a common silicon die). Configurations in which multiple semiconductor substrates are used in implementing array  80  and/or circuitry  82  and  98  may also be used. Sensor array  80  may include multiple sensors of the same type that have different sensitivities and/or ranges of operation (e.g., so that multiple sensor readings taken together can more effectively cover a desired range of potential sensor data values). and/or may include sensors of different types (e.g., to cover multiple different types of measured physical parameters such as temperature, pressure, gas concentration, strain, magnetic field, etc.). The array architecture of  FIG. 7  supports parallel data readout operations, because in an array with N columns, circuitry  90  can simultaneously gather N different resistive sensor measurements from the currently selected row. Circuit resources may be conserved, because it is not necessary to provide each sensor  37  with a dedicated readout circuit. For example, in an array with M rows, each of the M rows can share a common readout circuit (circuitry  90 ). 
     A flow chart of illustrative operations involved in gathering resistive sensor data from an array of resistive sensors and taking suitable action in electronic device  10  is shown in  FIG. 8 . 
     At step  100 , row decoder  84  may open switches  38  in array  80  to isolate resistive sensors  37  from column lines  88  and capacitors  50 . Circuitry  82  may also issue control signals for switches  46  that momentarily close switches  46  and supply initialization voltage Vi from output line  44  of digital-to-analog converter  42  to node  48  and capacitors  50 , thereby initializing capacitors  50  at voltage Vi. 
     At step  102 , row decoder  84  may close the switches  38  in a selected row of array  80 , thereby discharging capacitors  50  through the resistive sensors  37  in that row. Column readout circuitry  90  may monitor the discharge of capacitors  50  and may store count values from counter  96  in memory cells  94  of circuit  92  in response to toggling output signals from comparators  54 , thereby converting discharge time information (which relates to sensor resistance) into digital sensor readings. If additional resistance values from resistive sensors  37  are to be gathered (e.g., values from additional rows), the row to be monitored may be updated at step  104  and processing may loop back to step  100 , as shown by line  106 . If sufficient resistive sensor data has been gathered, suitable action may be taken at step  108  (e.g., information on sensor readings may be presented to a user on display  14 , an alert may be presented to a user, or other action may be taken using control circuitry  22 ). 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20161024
Publication Date: 20190521
Grant Date: 20190521
Priority Date: 20160405
Inventors: GUO, JIAN
Assignee: APPLE INC
CPC Classifications: [{"code": "G01D5/165", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/09", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/0094", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01R27/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/0023", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R33/09", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R27/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/0023", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01D5/165", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/0094", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 59958658