PATENT DOCUMENT

Publication Number: US-10446116-B2
Application Number: US-201715673138-A
Country: US
Kind Code: B2

Title: Temperature sensor on display active area

Abstract:
An apparatus is disclosed. In some examples, the apparatus comprises a display panel comprising a plurality of display pixels. In some examples, the apparatus comprises a plurality of temperature sensors disposed at different portions the display panel, wherein the plurality of temperature sensors comprise ratioed pairs of thin film transistors and the ratioed pairs of thin film transistors are formed on the display panel. In some examples, the apparatus comprises control circuitry for changing illumination properties of the plurality of display pixels based on changes is temperature detected by a proximate temperature sensor of the plurality of temperature sensors. In some examples, the ratioed pairs of thin film transistors are operated in a sub-threshold mode.

Claims:
What is claimed is: 
     
       1. An apparatus comprising:
 a display panel comprising display pixels; 
 a plurality of temperature sensors, the plurality of temperature sensors comprising transistors formed on a transistor layer in proximity to the display pixels, wherein the transistors of the plurality of temperature sensors are disposed within the display panel at different portions of the display panel; and 
 control circuitry for:
 changing illumination properties of a first plurality of the display pixels based on a first temperature detected by a first temperature sensor of the plurality of temperature sensors in proximity to the first plurality of the display pixels; and 
 changing illumination properties of a second plurality of the display pixels based on a second temperature, different from the first temperature, detected by a second temperature sensor of the plurality of temperature sensors in proximity to the second plurality of the display pixels. 
 
 
     
     
       2. The apparatus of  claim 1 , wherein the transistor layer is disposed between a backlight and a color filter substrate of the display panel. 
     
     
       3. The apparatus of  claim 1 , wherein the first temperature sensor of the plurality of temperature sensors comprises:
 a sense transistor configured to generate a temperature-dependent current; and 
 a threshold voltage compensation circuit coupled to the sense transistor, wherein the threshold voltage compensation circuit is configured to compensate for a threshold voltage of the sense transistor. 
 
     
     
       4. The apparatus of  claim 3 , wherein the threshold voltage compensation circuit compensates for the threshold voltage of the sense transistor by pre-charging a gate electrode of the sense transistor to the threshold voltage of the sense transistor. 
     
     
       5. The apparatus of  claim 4 , wherein compensating for the threshold voltage of the sense transistor comprises:
 coupling the gate electrode of the sense transistor and a drain electrode of the sense transistor together; 
 coupling the gate electrode of the sense transistor and the drain electrode of the sense transistor to a reference voltage level; 
 uncoupling the gate electrode of the sense transistor and the drain electrode of the sense transistor from the reference voltage level; 
 maintaining coupling of the gate electrode of the sense transistor and the drain electrode of the sense transistor while a gate voltage at the gate electrode of the sense transistor discharges to the threshold voltage of the sense transistor; and 
 uncoupling the gate electrode of the sense transistor and the drain electrode of the sense transistor. 
 
     
     
       6. The apparatus of  claim 5 , wherein generating the temperature-dependent current comprises applying a drive voltage to the gate electrode of the sense transistor. 
     
     
       7. The apparatus of  claim 6 , wherein the drive voltage is added to the threshold voltage of the sense transistor at the gate electrode of the sense transistor. 
     
     
       8. A method comprising:
 operating temperature sensor proximate to a display pixel in a display in a first temperature sensing mode; 
 determining whether a first characteristic of the temperature sensor is desired; and 
 in accordance with a determination that the first characteristic of the temperature sensor is desired, switching to a second temperature sensing mode. 
 
     
     
       9. The method of  claim 8 , wherein the first temperature sensing mode is a high accuracy mode and the second temperature sensor is a low power consumption mode. 
     
     
       10. The method of  claim 9 , wherein the low power consumption mode comprises operating at least one transistor of the temperature sensor in a subthreshold current region. 
     
     
       11. The method of  claim 8 , wherein the first characteristic is a reduced power consumption, and the determination of whether reduced power consumption is desired comprises comparing a battery power level of an electronic device including the display to a threshold battery power level. 
     
     
       12. The apparatus of  claim 3 , wherein the first temperature sensor of the plurality of temperature sensors is configured to sample a temperature-dependent voltage at a source of the sense transistor resulting from generating the temperature-dependent current. 
     
     
       13. The apparatus of  claim 3 , wherein the first temperature sensor of the plurality of temperature sensors further comprises a capacitor coupled between a source electrode of the sense transistor and ground. 
     
     
       14. The apparatus of  claim 13 , wherein the capacitor is configured to accumulate charge from the temperature-dependent current. 
     
     
       15. The apparatus of  claim 14 , wherein the first temperature sensor of the plurality of temperature sensors further comprises a discharge transistor coupled between the source electrode of the sense transistor and ground, wherein the discharge transistor is configured to discharge the capacitor prior to generating the temperature-dependent current. 
     
     
       16. The apparatus of  claim 6 , wherein the drive voltage is applied to the gate electrode of the sense transistor via an input capacitor. 
     
     
       17. The apparatus of  claim 5 , wherein:
 coupling the gate electrode of the sense transistor and the drain electrode of the sense transistor together comprises activating a first switching transistor coupled between the gate electrode of the sense transistor and the drain electrode of the sense transistor; 
 coupling the gate electrode of the sense transistor and the drain electrode of the sense transistor to the reference voltage level comprises activating a second switching transistor coupled between the drain electrode of the sense transistor and a power supply at the reference voltage level; 
 uncoupling the gate electrode of the sense transistor and the drain electrode of the sense transistor from the reference voltage level comprises deactivating the second switching transistor; 
 maintaining coupling of the gate electrode of the sense transistor and the drain electrode of the sense transistor comprises maintaining activation of the first switching transistor; and 
 uncoupling the gate electrode of the sense transistor and the drain electrode of the sense transistor comprises deactivating the first switching transistor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Patent Application No. 62/399,086, filed Sep. 23, 2016, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     This relates generally to electronics devices with displays, and more particularly to electronic devices with displays calibrated using temperature sensors. 
     BACKGROUND OF THE DISCLOSURE 
     Electronic devices such as computers, media players, cellular telephones, set-top boxes, and other electronic equipment can include displays for displaying visual information. Displays can be capable of displaying color images. In some instances, the color response of a display can change as the display operates. For example, changing operating conditions (e.g., display temperature) can affect the color response of the display. Some displays can depict white as somewhat yellowish when initially powered on and cold. As the display warms, the white point of the display can shift towards a more neutral white. Other display colors such as skin tone colors can also experience shifts within a color space as the temperature of the display changes. Similarly, other parameters such as luminance, black level, contrast, and/or electro-optical transfer function of the display can shift as a function of temperature. 
     The shift in color profile due to temperature changes in the display can cause one or more pixels in the display to change color until a stable operating temperature can be achieved. That is, although a display pixel may have a target color, which can remain the same for the initial temperature and the stable operating temperature, the actual color displayed, as objectively measured by its chromaticity and luminance, can vary. Displays can be calibrated to account for temperature induced color shifts by, for example, applying adjustment factors to display pixel values based on temperature(s) measured by one or more temperature sensors. 
     SUMMARY OF THE DISCLOSURE 
     This relates to one or more temperature sensors included in a display and methods for operating thereof. Examples of the disclosure can include one or more temperature sensors located in close proximity (e.g., on the TFT glass) to pixel material, thereby reducing temperature differences (e.g., between measured and actual temperatures) and sensing errors. In some examples, the TFT array and/or conductive material in the active area of the touch screen can be utilized for implementing the temperature sensors. The one or more temperature sensors can be configured to measure a V GS  difference across a pair of transistors, a current indicative of temperature-dependent mobility, and/or the resistance, indicative of temperature, of a conductive material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  illustrate systems in which examples of the disclosure can be implemented. 
         FIG. 2A  illustrates a block diagram of an exemplary display and various included components according to examples of the disclosure. 
         FIG. 2B  illustrates a perspective view of an exemplary stackup included in a touch screen according to examples of the disclosure. 
         FIG. 3  illustrates an exemplary circuit for measuring the temperature of the display pixels according to examples of the disclosure. 
         FIG. 4A  illustrates an exemplary circuit for measuring the temperature of the display pixels according to examples of the disclosure. 
         FIG. 4B  illustrates an exemplar plot of temperature and voltage dependent relationships between gate voltage and drain current of a transistor according to examples of the disclosure. 
         FIG. 5A  illustrates a top view of an exemplary layout of one or more temperature sensors according to examples of the disclosure. 
         FIG. 5B  illustrates an exemplary method for dynamically changing the temperature sensor operation according to examples of the disclosure. 
         FIG. 6A  illustrates an exemplary temperature sensor according to examples of the disclosure. 
         FIG. 6B  illustrates an exemplary timing diagram for the operation of circuit to sense temperature sensor according to examples of the disclosure. 
         FIG. 7A  illustrates exemplary sense circuitry for sampling a temperature sensor according to examples of the disclosure. 
         FIG. 7B  illustrates an exemplary graph of the correlation between temperature and resistance of a temperature sensor according to examples of the disclosure. 
         FIG. 7C  illustrates an exemplary temperature sensor according to examples of the disclosure. 
         FIG. 7D  illustrates a table of exemplary temperature sensor dimensions according to examples of the disclosure. 
         FIG. 7E  illustrates an exemplary temperature sensor with a plurality of connection points according to examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the various examples. 
     Various techniques and process flow steps will be described in detail with reference to examples as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects and/or features described or referenced herein. It will be apparent, however, to one skilled in the art, that one or more aspects and/or features described or referenced herein may be practiced without some or all of these specific details. In other instances, well-known process steps and/or structures have not been described in detail in order to not obscure some of the aspects and/or features described or referenced herein. 
     Further, although process steps or method steps can be described in a sequential order, such processes and methods can be configured to work in any suitable order. In other words, any sequence or order of steps that can be described in the disclosure does not, in and of itself, indicate a requirement that the steps be performed in that order. Further, some steps may be performed simultaneously despite being described or implied as occurring non-simultaneously (e.g., because one step is described after the other step). Moreover, the illustration of a process by its depiction in a drawing does not imply that the illustrated process is exclusive of other variations and modification thereto, does not imply that the illustrated process or any of its steps are necessary to one or more of the examples, and does not imply that the illustrated process is preferred. 
     Electronic devices such as cellular telephones, media players, computers, set-top boxes, wireless access points, and other electronic equipment can include displays. Displays can be used to present visual information and status data and/or may be used to gather user input data. The displays can be configured to display color images. For example, displays can include color display pixels configured to create colored light. Individual pixels of a display can receive a red, green, and blue value that can together define the color to be created by the pixel. These red, green, and blue values can be sometimes referred to herein as “RGB value.” 
     Without compensation, display colors can shift within a color space as the temperature of the display varies. To account for changes in display operating temperature, display colors can be adjusted using one or more adjustment values. For example, an adjustment value can be applied to an input RGB value to obtain an adapted RGB value that can account for changes in display temperature. The adjustment value can be stored in a look-up table or can be computed by interpolating from the values found in the table, for example. The adjustment value can be applied, depending on the type of display, to a RGB value that can be supplied to a display pixel or to the gain of a red channel, green channel, and blue channel to adjust the colors of the display. Display colors can be corrected as the display warms up, for example, and changes temperature. Display performance information (e.g., luminance and chromaticity values) can be recorded for different RGB input values. 
     This relates to one or more temperature sensors included in a display and methods for operating thereof. Examples of the disclosure can include one or more temperature sensors located in close proximity (e.g., on the TFT glass) to pixel material, thereby reducing temperature differences and sensing errors. In some examples, the TFT array and/or conductive material in the active area of the touch screen can be utilized for implementing the temperature sensors. The one or more temperature sensors can be configured to measure a V GS  difference across a pair of transistors, a current indicative of temperature-dependent mobility, and/or the resistance, indicative of temperature, of the conductive material. 
       FIGS. 1A-1C  illustrate systems in which examples of the disclosure can be implemented.  FIG. 1A  illustrates an exemplary mobile telephone  136  that can include a touch screen  124 .  FIG. 1B  illustrates an exemplary media player  140  that can include a touch screen  126 .  FIG. 1C  illustrates an exemplary wearable device  144  that can include a touch screen  128  and can be attached to a user using a strap  146 . The systems of  FIGS. 1A-1C  can utilize the temperature sensors, configurations, and methods for operation thereof, as will be disclosed. 
     Touch screen  124 , touch screen  126 , and/or touch screen  128  can include a display that can incorporate capacitive touch electrodes or other touch components. In some examples, the systems can include a display that is not touch-sensitive. The display can include image pixels formed from light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), plasma cells, electrophoretic display elements, electrowetting display elements, liquid crystal display (LCD) components, or other suitable image pixel structures. Arrangements in which the display is formed using LCD pixels are sometimes described herein as an example. This is, however, merely illustrative. Any suitable type of display technology can be used in forming the display if desired. The touch screen can be substantially filled with active display pixels or may have an active portion or an inactive portion. 
       FIG. 2A  illustrates a block diagram of an exemplary display and various included components according to examples of the disclosure.  FIG. 2B  illustrates a perspective view of an exemplary stackup included in a touch screen according to examples of the disclosure. Touch screen  220  can include a backlight controller  238  that can govern operation of backlight  232 . For example, backlight controller  238  can include one or more driver integrated circuits that can power and drive light source  236 . 
     Touch screen  220  can include a LCD controller  240  that can govern operation of pixel material  215 . For example, LCD controller  240  can receive image data through input channels  242 A,  242 B, and  242 C of touch screen  220 . In some examples, the image data can be sent to touch screen  220  from a graphics card, controller, or processor through an I/O controller. Each input channel  242 A,  242 B, and  242 C can correspond to a different color channel of touch screen  220 . For example, input channel  242 A can be a red input channel; input channel  242 B can be a green input channel; and input channel  242 C can be a blue input channel. LCD controller  240  can process the image data received through channels  242 A,  242 B, and  242 C and can provide the processed image data to drivers  246  in the form of output signals  244 A,  244 B, and  244 C. Each output signal  244 A,  244 B, and  244 C can represent the processed image data from a corresponding input channel  242 A,  242 B, and  242 C. In some examples, LCD controller  240  can include control circuitry and/or one or more microprocessors for processing the image data. 
     Each display pixel  248  can include a set of subpixels  250 A,  250 B, and  250 C, each capable of emitting a discrete color. For example, subpixels  250 A can emit red light; subpixels  250 B can emit green light; and subpixels  250 C can emit blue light. Each subpixel  250 A,  250 B, and  250 C can display image data from the corresponding output signal  244 A,  244 B, and  244 C, respectively. A number of colors can be displayed by each pixel  248  by varying the individual intensity levels of the subpixels  250 A,  250 B, and  250 C. 
     Touch screen  220  can include other light-emitting components such as reflective components, liquid crystal display (LCD) components, organic light-emitting diode (OLED) components, or other suitable display pixel structures. To provide touch screen  220  with the ability to display color images, the light-emitting components can have color filter elements. Each color filter element can be used to impart color to the light associated with a respective display pixel  248 . 
     Display control circuit  228  can also include display driver circuitry. Display driver circuitry can be implemented using one or more integrated circuits (ICs) and may sometimes be referred to as a driver IC, display driver integrated circuit, or display driver. Display driver circuitry may include, for example, timing controller (TCON) circuitry such as a TCON integrated circuit. If desired, display driver circuitry can be mounted on an edge of a thin-film-transistor (TFT) substrate layer (e.g., TFT glass  209 ) in touch screen  220 , for example. Display control circuit  228  can be coupled to additional circuitry (e.g., storage and processing circuitry). 
     There can be tens, hundreds, or thousands of rows and columns of display pixels  248 . Each pixel  248  can, if desired, be a color pixel such as a red (R) pixel, a green (G) pixel, a blue (B) pixel or a pixel of another color. Red pixels R, for example, can include a red color filter element (e.g., color filter  205 ) over a light generating element (e.g., a liquid crystal pixel or an OLED pixel element) that can absorb and/or reflect non-red light while passing red light. This is, however, merely illustrative. Display pixels  248  can include any suitable structures for generating light of a given color. For example, display pixels  248  can include a pattern of cyan, magenta, and yellow pixels or can include any other suitable pattern of colors. Arrangements of display pixels  248  including a pattern of red, green, and blue pixels are sometimes desired herein as an example. 
     Display control circuit  228  such as a display driver integrated circuit and, if desired, associated thin-film transistor circuitry formed on a display substrate layer can be used to produce signals such as data signals and gate line signals (e.g., on data lines and gate lines respectively in touch screen  220 ) for operating display pixels (e.g., turning display pixels  248  on and/or off and/or adjusting the intensity of display pixels  248 ). During operation, display control circuit  228  can control the values of the data signals and gate signals to control the light intensity associated with each of the display pixels and to thereby display images on touch screen  220 . 
     Display control circuit  228  can be used to convert input RGB values for each display pixel  248  into analog display signals for controlling the brightness of each display pixel. Control circuitry (e.g., storage and processing circuitry) can provide input RGB values (e.g., integers with values ranging from 0 to 255) that can correspond to the desired pixel intensity of each pixel  248  to display control circuit  228 . For example, a digital display control value of 0 may result in an “off” pixel, whereas a digital display control value of 255 may result in a display pixel operating at a maximum available power. 
     Display control circuit  228  can be used to concurrently operate display pixels  248  of different colors in order to generate light having a color that is a mixture of, for example, primary colors: red, green, and blue. For example, operating red pixels R and blue pixels B at equal intensities can generate light that appears violet; operating red pixels R and green pixels G at equal intensities can generate light that appears yellow; operating red pixel R and green pixels G at half of maximum intensity can generate light that appears yellowish; and operating red pixels R, green pixels G, and blue pixels B simultaneously at maximum intensity can generate light that appears white, etc. 
     Touch screen  220  can also include one or more temperature sensors  252 . Temperature sensors  252  can be internal sensors configured to gather temperature information. For example, temperature sensors  252  can be used to measure display temperature, display cover material temperature (e.g., the temperature associated with a cover material that covers touch screen  220 ), backlight temperature (e.g., the temperature associated with light-emitting diodes that provide the backlight for touch screen  220 ), internal component temperature (e.g., the temperature associated with an internal component of the device), etc. 
     Temperature sensors  252  can be configured to measure the temperature at different locations on touch screen  220 . For example, temperature sensors  252  can be included in TCON circuitry, which can be mounted on one or more locations (e.g., an edge) of a TFT substrate layer in touch screen  220 , for example. Additionally or alternatively, temperature sensors  252  can be included located at other locations of the display. Touch screen  220  can include a backlight  232  that can function as a light source for displaying one or more images and can be assembled within frame  234 . In some examples, frame  234  can be included in a housing of the device. 
     Color filter glass  203  can include a plurality of color filters  205 . In some examples, color filters  205  can include three colors: blue (B), green (G), and red (R), such as in a RGB display. Color filter glass  203  can also include one or more electrodes for touch sensing (e.g., sense line  223 ). TFT glass  209  can include circuit elements  211 . Circuit elements  211  can be, for example, multi-function circuit elements that can operate as part of the display circuitry (e.g., LCD controller  240 ) of the touch screen  220  and also as part of the touch sensing circuitry of the touch screen  220 . In some examples, circuit element  211  can be single-function circuit elements that can operate only as part of the touch sensing system. In addition to circuit elements  211 , other circuit elements (not shown) can be formed on TFT glass  209 , such as transistors, capacitors, conductive vias, data lines, gate lines, etc. Circuit elements  211  and other circuit elements formed on TFT glass  209  can operate together to perform various display functionality required for the type of display technology used by touch screen  220 . The circuit elements can include, for example, elements that can exist in LCD displays. Some of the circuit elements  211  can be electrically connected together to form touch electrodes (e.g., drive lines  222 ). Although color filter glass  203  and TFT glass  209  are referred to as “glass,” examples of the disclosure can include any type of transparent substrates capable of supporting the components including, but not limited to, plastic. 
     Pixel material  215  can be disposed between TFT glass  209  and color filter glass  203 . Pixel material  215  can be separate regions or cells above circuit elements  211 . For example, when the pixel material is a liquid crystal, these regions or cells are meant to illustrate regions of the liquid crystal controlled by the electric field produced by the pixel electrode and common electrode of the region or cell under consideration. Pixel material  215  can be a material that, when operated on or by the display circuitry of touch screen  220 , can generate or control an amount, color, etc., of light produced by each display pixel. For example, in a LCD touch screen, pixel material  215  can be formed of liquid crystal, with each display pixel controlling a region or cell of the liquid crystal. In this case, for example, various methods can exist for operating liquid crystal in a display operation to control the amount of light (from backlight  232 ) emanating from each display pixel  248  (e.g., by applying an electric field in a particular direction depending on the type of LCD technology employed by the touch screen). In an in-plane switching (IPS), fringe field switching (FFS), and advanced fringe field switching (AFFS) LCD displays, for example, electrical fields between pixel electrodes and common electrodes (Vcom) disposed on the same side of liquid crystal can operate on the liquid crystal material to control the amount of light from backlight  232  that can pass through the display pixel. In an OLED (organic light emitting diode) display, for example, pixel material  215  can be an organic material that can generate light when a voltage is applied across the material. 
     Backlight  232  can include one or more light sources  236 , as well as other components such as a light guide and optical films that can direct light from light source  236  towards pixel material  215 . In some examples, light source  236  can include a cold-cathode fluorescent lamp (CCFL), one or more LEDs, OLEDs, or any other suitable source of light. Backlight  232  can be an edge-lit backlight that includes one light source  236  located at an edge of touch screen  220 . In some examples, multiple light sources  236  can be disposed around one or more edges of touch screen  220 . In some examples, instead of an edge-lit backlight, the backlight can be a direct-light backlight with one or more light sources  236  mounted behind pixel material  215 . 
     Display calibration information such as color-specific and temperature-specific adjustment values can be loaded onto the device during manufacturing, for example. The stored adjustment values can be used to adjust display colors in order to compensate for changes in display temperature. Adjustment values can be stored in any suitable location in the device. For example, adjustment values can be stored in display control circuit  228 . 
     In some examples, a display TCON integrated circuit (included in display control circuit  228 ) can receive input RGB values and can receive display temperature information from temperature sensors  252 . Based on the input RGB values and temperature information, the TCON integrated circuit can determine a color-specific and temperature-specific adjustment value for each input RGB value. The TCON integrated circuitry can apply the adjustment values to either the input RGB values or to the gain control of the RGB channels. The adjustment values can change the display colors such that the display colors appear as the target color. 
     Due to variations in display temperature, some internal parameters of the display can change, which can in turn affect the luminance and/or the chromaticity of the displayed color, even if the RGB input signal has not changed. For example, displayed color can vary with temperature. At an initial power-on state, a display can have an initial white point that can appear on the display as a yellowish color. As time passes, the physical display temperature can change (e.g., increase to a stable value). The increase in display temperature can induce a corresponding change in the display white point. For example, as the display warms up to a stable operating temperature, the display white point may shift and may appear as a neutral white. If the display continues to warm up beyond a stable operating temperature, the display white point may appear slightly blue. 
     Displays can sometimes be calibrated to minimize temperature induced white point shifts. Methods can include applying adjustment values to RGB input values based on a temperature measured at the center of the display. During calibration operations, information can be gathered from the device such as temperature information measured using temperature sensors  252 . Temperature sensor  252  can, for example, be an internal sensor in the device. Temperature sensor  252  can be used to measure any suitable temperature associated with the device (e.g., display temperature, display cover material temperature, backlight temperature, internal component temperature, etc.). 
     Although temperature sensors can be located, for example, on the main logic board, on a board that excludes the LCD controller (e.g., in TCON circuitry), and/or along one or more areas of the housing frame, a difference can exist between the actual temperature of a display pixel and temperature measured at the temperature sensors. Examples of the disclosure can include one or more temperature sensors located in close proximity (e.g., on the TFT glass) to pixel material, thereby reducing temperature differences and sensing errors. In some examples, the TFT array and/or conductive material in the active area of the touch screen can be utilized for implementing the temperature sensors. 
       FIG. 3  illustrates an exemplary circuit for measuring the temperature of the display pixels according to examples of the disclosure. In some examples, the temperature sensors can be configured to measure the V GS  difference of a ratioed TFT pair biased under constant current. Circuit  300  can include a plurality of transistors (e.g., transistor  310 , transistor  312 , transistor  314 , and transistor  316 ) and resistors (e.g., resistor  320  and resistor  322 ) located in the active area  302  of the display. For transistor  310 , the drain can be directly connected to resistor  320  (e.g., a routing resistance between the current source and transistor  310 ); the gate can be connected to the drain; and the source can be directly connected to the drain of transistor  312 . For transistor  312 , the drain can be directly connected to the source of transistor  310 , and the gate can be connected to the drain. For transistor  314 , the drain can be directly connected to resistor  322  e.g., a routing resistance between the current source and transistor  314 ); the gate can be connected to the drain; and the source can be directly connected to the drain of transistor  316 ; and. For transistor  316 , the drain can be directly connected to the source of transistor  314 , and the gate can be connected to the drain. In this manner, two pairs of TFTs can be included in active area  302 . 
     The size of transistor  310 , transistor  312 , transistor  314 , and transistor  316  can be configured with desired W/L (width to length) ratios. In some examples, the transistors can be configured such that the lengths are the same, but the widths have a certain ratio relationship for achieving the desired W/L ratio for each transistor. For example, the width of transistor  310  can be smaller than the width of transistor  314 , where the ratio of the widths can be 1:M. The width of transistor  312  can be greater than the width of transistor  316 , where the ratio of the widths can be M:1. In some examples, the voltage levels at the drain of transistor  310  and the drain of transistor  314  can be the same, such that the voltage levels “seen” by current source  336  (i.e., the voltage at the source of each of the current mirror transistors  330  and  332 ) can also be the same. In some examples, resistor  320  and resistor  322  can have the same resistance values. It should be understood from the above that by maintaining a constant length for the transistors  310 ,  312 ,  314 , and  316  above, changing the values of W can produce a desired value of W/L. In the above described configuration, the ratio of W/L between transistors  312  and  316  can be M:1 and the ratio of W/L between transistors  310  and  314  and be 1:M. It should be understood that the same ratios of W/L can be achieved by changing value of W, L, or both for the transistors  310 ,  312 ,  314 , and  316 . 
     Circuit  300  can further include one or more additional transistors (e.g., transistor  330 , transistor  332 , and transistor  334 ) and at least one source (e.g., source  336 ). The additional transistors and current source can supply a current through each pair of TFTs. The transistors  330  and  332  can act as current mirrors for the current supplied by current source  336 , and can be configured to provide equal current to both transistor pairs  310 / 312  and  314 / 316  respectively. An amplifier  340  can be electrically coupled to the TFT pairs, and a V GS  difference between transistor  312  and transistor  316  can be measured. In some examples, amplifier  340  can be a differential amplifier. Based on the V GS  difference ΔV GS , the temperature of the display and/or touch sensor panel at the location of the TFT pairs can be determined using, for example, Equation 1: 
                     Δ   ⁢           ⁢       V   GS     ⁡     (     T   g     )         =             I     d   ⁢           ⁢   2       ⁡     (     T   b     )             μ   02     ⁡     (     T   g     )       ⁢     C   ox     ⁢       W   2       L   2             -           I     d   ⁢           ⁢   1       ⁡     (     T   b     )             μ   01     ⁡     (     T   g     )       ⁢     C   ox     ⁢       W   1       L   1                       (   1   )               
where I d1  and I d2  can be equal to the currents supplied by source  336  and mirrored by transistors  330  and  332 , μ 01  and μ 02  can be the carrier mobility, W 1  and W 2  can be the widths, L 1  and L 2  can be the lengths, C ox  can be the oxide capacitance, T b  can be the temperature of the current mirror transistors  330  and  332 , and T g  can be the glass temperature (e.g., TFT glass  209  illustrated in  FIG. 2B ). The mobility can be affected by the temperature, which can be accounted for when determining the temperature T g  from the measured V GS . As shown by the equation, ΔV GS  can have a non-linear relationship with respect to temperature T g  of the transistors.
 
       FIG. 4A  illustrates a second exemplary circuit for measuring the temperature of the display pixels according to examples of the disclosure. In some examples, the temperature sensors can be configured to measure a V GS  difference for two TFTs based on the exponential relationship to the bias current in a subthreshold bias region. Circuit  400  can include a plurality of transistors (e.g., transistor  410  and transistor  412 ) and a plurality of current sources (e.g., current source  436  and current source  438 ). In some examples, transistor  410  and transistor  412  can be located in the active area (e.g., active area  302  illustrated in  FIG. 3 ) of the display. For transistor  410 , the drain can be directly connected to current source  436 ; the gate can be connected to the drain; and the source can be connected to ground. For transistor  412 , the drain can be directly connected to current source  438 ; the gate can be connected to the drain; and the source can be connected to ground. The size of transistor  410  and transistor  412  can be configured such that the W/L ratio of the transistors can have a desired relationship. For example, the W/L ratio of transistor  410  can be smaller than the W/L ratio of transistor  414 , where the ratio of W/L can be 1:M (where M is an integer). 
     Current source  436  and current source  438  can be configured to supply different currents to transistor  410  and transistor  412 , respectively. For example, current source  436  can be configured to supply a current that is (an integer) N times greater than the current supplied by current source  438 . In some examples, N can be equal to the inverse of the M (i.e., N=1/M, where M is related to the ratio of the W/L of transistor  410  and transistor  412 ). It should be understood that based on the sizing and bias relationships described above, the transistor  410  can have a current density N*M times greater than transistor  412 . 
     The transistors  410  and  412  can be biased at a low current level such that V GS  can be determined by the exponential relationship to the bias current (e.g., in a subthreshold region of operation). As illustrated in  FIG. 4B , the bias current level for transistors  410  and  412  can include a current in region  403 , which can be a region where the logarithmic plot of drain current I D  with respect to the gate voltage V g  can have a linear relationship. The linear relationship is illustrated with line  405  having a slope equal to 1/SS, where SS is equal to subthreshold swing (i.e., thermal voltage kT/q). 
     An amplifier  440  can be electrically coupled to transistor  410  and transistor  412 , and a V GS  difference between the two transistors can be measured. In some examples, amplifier  340  can be a differential amplifier. Based on the V GS  difference ΔV GS , the temperature of the display and/or touch sensor panel at the location of the transistors can be determined using, for example, Equations 2-5: 
                     N   ×     I   bias       =       I   0     ×     e       V     GS   ⁢           ⁢   1       SS                 (   2   )                 I   bias     =       MI   0     ×     e       V     GS   ⁢           ⁢   2       SS                 (   3   )                 ln   ⁡     (       N   ×     I   bias           I   bias     /   M       )       =       Δ   ⁢           ⁢     V   GS       SS             (   4   )                 Δ   ⁢           ⁢     V   GS       =         ln   ⁡     (     N   ×   M     )       ×   SS     =       ln   ⁡     (   NM   )       ×       kT   g     q                 (   5   )               
where I bias  is the current supplied by source  438 , N and M can be integers related to the relative widths of transistor  410  and transistor  412  (discussed above), V GS1  and V GS2  can be the V GS  values measured by amplifier  440 , and SS can be the subthreshold swing (related to the temperature of the transistors T g ).
 
       FIG. 5A  illustrates a top view of an exemplary layout of one or more temperature sensors according to examples of the disclosure. TFT array  500  can include plurality of TFTs  511  and plurality of TFTs  513 . Plurality of TFTs  511  and plurality of TFTs  513  can include a plurality of transistors electrically coupled together. For example, the gates in all of the plurality of TFTs  511  can be electrically coupled together. In some examples, plurality of TFTs  511  can include transistors having one or more of the same characteristics as the transistors included in plurality of TFTs  513 . The number of electrically-coupled transistors included in plurality of TFTs  511  can be less than the number of electrically-coupled transistors included in plurality of TFTs  513 . For example, X (e.g., 2) number of electrically-coupled transistors can be included in plurality of TFTs  511 , while Y (e.g., where Y=X×M) number of electrically-coupled transistors can be included in plurality of TFTs  513 . The factor M can correspond to the 1:M and M:1 ratios of W/L described above in  FIGS. 3 and 4 . Plurality of TFTs  511  can have the same operation and characteristics as transistor  310  (illustrated in  FIG. 3 ), transistor  312  (illustrated in  FIG. 3 ), and/or transistor  410  (illustrated in  FIG. 4A ); plurality of TFTs  513  can have the same operation and characteristics as transistor  314  (illustrated in  FIG. 3 ), transistor  316  (illustrated in  FIG. 3 ) and/or transistor  412  (illustrated in  FIG. 4A ). 
     Plurality of TFTs  511  can be electrically coupled to conductive section  541 . Conductive section  541  can be coupled to an amplifier (e.g., amplifier  340  illustrated in  FIG. 3  or amplifier  440  illustrated in  FIG. 4A ). Plurality of TFTs  513  can be electrically coupled to conductive section  531 . Conductive section  531  can be coupled to one or more current sources (e.g., current source  336  illustrated in  FIG. 3 , current source  436  illustrated in  FIG. 4A , or current source  438  illustrated in  FIG. 4A ). Conductive section  521  can be provided for providing a grounded connection to the substrate of TFTs  511  and  513 . Conductive section  531 , conductive section  541 , and conductive section  521  can be, for example, routing traces. 
     In some examples, one or more of the transistors can be located on the same substrate. The substrate can be, for example, a color filter glass (e.g., color filter glass  203  illustrated in  FIG. 2B ), a TFT glass (e.g., TFT glass  209  illustrated in  FIG. 2B ), or a separate substrate located in close proximity to the display. Although  FIG. 5A  illustrates the TFTs as being located in close proximity (e.g., adjacent) to each other, examples of the disclosure can include one or more other (e.g., non-TFT) components located between the TFTs. For example, some of the plurality of TFTs can be located on a first side (e.g., left side) of the TFT glass, while others of the plurality of TFTs can be located on a second side (e.g., right side) of the TFT glass). Additionally or alternatively, one or more of the non-TFT components including, but not limited to, the amplifier, one or more sources, and routing traces can be located on a separate substrate (e.g., logic board). 
     TFT array  500  can further include one or more dummy TFTs  518 . Dummy TFTs  518  can be the same type of transistors as those included in plurality of TFTs  511  and/or plurality of TFTs  513 . In some examples, dummy TFTs  518  can be floating (e.g., not electrically coupled to a source or other transistors) or coupled to ground. Dummy TFTs  518  can be located around the edges of the substrate to account for edge variations during manufacture, for example. 
     Examples of the disclosure can include using both types of temperature sensor operations as illustrated in  FIGS. 3 and 4A .  FIG. 5B  illustrates an exemplary method for dynamically changing the temperature sensor operation according to examples of the disclosure. It can be recognized from the figures above that transistors  312  and  316  in  FIG. 3  can directly correspond to transistors  412  and  410  (respectively) in  FIG. 4A . A controller or processor can select which temperature sensor operation based on one or more characteristics. For example, the controller can determine whether a first characteristic (e.g., lower power consumption) is desired (step  552  of process  550 ). If the first characteristic is desired, then the controller can switch to the first temperature sensor operation (step  554  of process  550 ). The first temperature sensor operation can include, for example, measuring the temperature using lower currents corresponding to a subthreshold region of operation of the TFTs (e.g., currents from current source  436  and current source  438  illustrated in  FIG. 4A ). The controller can determine whether a second characteristic (e.g., enhanced measurement accuracy) is desired (step  556  of process  550 ). If the second characteristic is desired, then the controller can switch to the second temperature sensor operation (step  558  of process  550 ). The second temperature sensor operation can include, for example, measuring the temperature using higher currents (e.g., current from current source  336  illustrated in  FIG. 3 ). If the first characteristic is not desired (e.g., step  552 ), the controller can determine whether the second characteristic is desired (e.g., step  556 ). The process can be repeated when the controller measures the temperature again (step  560  of process  550 ). 
     With dynamically changing the temperature sensor operations, the device can be capable of measuring a plurality of temperature values of the display while retaining the desired characteristics such as low power consumption and/or enhanced measurement accuracy. Examples of the disclosure can include measuring the temperature using both temperature sensor operations, comparing the values, and discarding (or averaging) the values. 
       FIG. 6A  illustrates an exemplary temperature sensor circuit  600  according to examples of the disclosure. In some examples, temperature sensor transistor  602  can be a MOSFET, TFT, or other type of transistor. Temperature sensor transistor  602  can be coupled to a temperature sensor circuit  600  to create a threshold compensated temperature-dependent current, as will be described. Temperature sensor circuit  600  can include VDD transistor  604 , gate transistor  606 , source transistor  608 , gate capacitor  610 , storage capacitor  612 , and temperature sensor transistor  602 , for example. In some examples, gate capacitor  610  can be coupled to a drive voltage  620 . Temperature sensor transistor  602  can have a drain  614 , gate  616 , and source  618 , for example. 
     In some examples, the drain of VDD transistor  604  can be coupled to power supply VDD, and the source can be coupled to both the drain of gate transistor  606  and the drain  614  of temperature sensor transistor  602 . The source of gate transistor  606  can be coupled to the gate  616  of temperature sensor transistor  602  and gate capacitor  610 , for example. In some examples, the drain of source transistor  608  can be coupled to the source  618  of temperature sensor transistor  602 , and the source can be coupled to GND. The drain of source transistor  608  can be further coupled to a first terminal of storage capacitor  612 , for example. Second terminal of storage capacitor  612  can be coupled to ground. 
     Although temperature sensor transistor  602  is illustrated as being an N-channel MOSFET, in some examples, other transistor types (e.g., P-channel MOSFET) can be used. Further, although VDD transistor  604 , gate transistor  606 , and source transistor  608  are illustrated as being N-channel MOSFETs, in some examples, other switches, transistors, and/or components are possible. The operation of temperature sensor circuit  600  will now be described with reference to  FIG. 6B . 
       FIG. 6B  illustrates an exemplary timing diagram for the operation of temperature sensor circuit  600  to temperature based on temperature sensor transistor  602  according to examples of the disclosure. As will be described below, in some examples, temperature sensor circuit  600  can be operated to cause temperature sensor transistor  602  to produce a threshold voltage compensated temperature-dependent current. The temperature dependent current can cause a charge to accumulate at different rates on storage capacitor  612 , resulting in a temperature-dependent voltage at the source  618  of the temperature sensor transistor  602 . The temperature-dependent voltage can be measured to determine temperature, for example. In the plots of  FIG. 6B , each plot illustrates one or more voltages that can be present at specific nodes in the circuit  600  illustrated in  FIG. 6A . The first plot in  FIG. 6B  illustrates a voltage that can be applied to the gate of VDD transistor  604  labeled as  604 ′. The second plot in  FIG. 6B  illustrates a voltage that can be applied to the gate of gate transistor  606  (labeled as  606 ′) and a voltage at drain  614 . The third plot in  FIG. 6B  illustrates a voltage at gate  616  and a voltage that can be applied at drive voltage  620 . The fourth plot in  FIG. 6D  illustrates a voltage that can be applied to the gate of source transistor  608  (labeled as  608 ′) and a voltage at source  618  (i.e., a voltage across capacitor  612 ). 
     From time t 0  to t 1 , VDD transistor  604  can be activated (e.g., by a applying a high voltage to the gate of the VDD transistor) to apply a voltage VDD to the drain  614  of temperature sensor transistor  602  and the drain of gate transistor  606 . Starting at t 0 , gate transistor  606  can also be activated (e.g., by applying a high voltage to the gate of the gate transistor) to apply a voltage of VDD to the gate  616  of temperature sensor transistor  602 . In this manner, from t 0  to t 1 , the source  618  of temperature sensor transistor  602  can have a positive voltage that can be equal to VDD minus the gate to source voltage (V gs ) of the temperature sensor transistor. 
     In some examples, from t 1  to t 2 , gate transistor  606  can continue to be activated and source transistor  608  can become activated. The voltage of the source  618  of temperature sensor transistor  602  can cause a current to flow through the source transistor  608 , for example. In some examples, the voltage of the source  618  of the temperature sensor transistor  602  can become equal to ground as the accumulated charge on storage capacitor  612  can be discharged through source transistor  608 . At t 1 , VDD transistor  604  can be deactivated, which can cause the drain  614  of temperature sensor transistor  602  to be at a floating voltage level. Likewise, the gate  616  of temperature sensor transistor  602  can also be at a floating voltage level. In some examples, as current flows through transistor  602 , the floating voltage level of drain  614  and gate  616  can decrease until the voltage level reaches a threshold voltage of the temperature sensor transistor  602  and current flow cuts off. 
     From t 2  to t 3 , gate transistor  606  and source transistor  608  can be deactivated, for example. In some examples, the source  614  and gate  616  of temperature sensor transistor  602  can remain at the same voltage level, which can be equal to the threshold voltage of the temperature sensor transistor  602 . The source  618  of temperature sensor transistor  602  can remain at a voltage level equal to GND, for example. 
     In some examples, from t 3  to t 4 , a drive voltage  620  can be applied to gate capacitor  610 . The gate capacitor  610  can couple gate  616  of temperature sensor transistor  602  to the drive voltage  620 , for example. Accordingly, the voltage of the gate  616  of the temperature sensor transistor  602  can, for example, be equal to the sum of the drive voltage  620  and the threshold voltage of the temperature sensor. In some examples, variations in threshold voltage of temperature sensor  602  can be canceled out by pre-charging the gate  616  of the temperature sensor transistor with the threshold voltage as described above. In some examples, the source  618  of temperature sensor transistor  602  can continue to have a voltage equal to ground. The drain  614  of temperature sensor transistor  602  can continue to have a floating voltage, which can be equal to the threshold voltage of temperature sensor transistor  602 , for example. 
     In some examples, from t 4  to t 5  VDD transistor  604  can be activated, which can cause the drain  614  of temperature sensor transistor  602  to have a voltage level of VDD. Accordingly, a path for current flow can be created through VDD transistor  604  and current can flow through temperature sensor transistor  602 , for example. In some examples, the amount of current flowing through temperature sensor transistor  602  can be dependent on the temperature of temperature sensor transistor  602 . The current flowing through temperature sensor  602  can cause storage capacitor  612  to accumulate a voltage at the source  618  of the temperature sensor transistor  602  at a rate proportional to the current. Accordingly, the time from t 4  to t 5  can be an integration window of the temperature sensor transistor  602  current. 
     From t 5  to t 6 , VDD transistor  604  can be deactivated, for example. In some examples, from t 5  to t 6 , the voltage of the source  618  of the temperature sensor transistor  602  can remain a constant value. The voltage at source  618  can be sampled to determine the temperature of temperature sensor transistor  602 . 
       FIG. 7A  illustrates exemplary sense circuitry  700  for sampling a temperature sensor  702  according to examples of the disclosure. In some examples, circuitry  700  can include a temperature sensor  702 , a current source  704 , an amplifier  706 , and an ADC  708 . The temperature sensor  702  can be coupled to the current source  704 , amplifier  706 , and ground  710  through routing traces  712 , for example. In some examples, routing traces  712  can have resistances  714 . 
     During operation, current source  704  can apply a current through temperature sensor  702 , for example. In some examples, a voltage across the temperature sensor  702  can be measured at amplifier  706 . The output of amplifier  706  can be converted from an analog signal to a digital signal at ADC  708  for further processing. In some examples, a processor or controller can be operatively coupled to ADC  708  to receive a signal indicative of voltage across temperature sensor  702 . The resistance of the temperature sensor  702  can be determined based on the received signal, the known current at current source  704  and the known resistances  714  of routing traces  712 . In some examples, the resistance of temperature sensor  702  can be indicative of its temperature. For example, resistance can be correlated to temperature as shown below in  FIG. 7B . 
       FIG. 7B  illustrates an exemplary graph  720  of the correlation between temperature  722  and resistance  724  of a temperature sensor according to examples of the disclosure. In some examples, as shown in graph  720 , as temperature  724  increases, the resistance  722  of temperature sensor  702  can increase. Graph  720  can be determined based on a calibration procedure in which known temperatures are applied to temperature sensor  702  while measuring its resistance, for example. In some examples, the calibration data can be used to determine a function or a lookup table (LUT) for calculating temperature based on the resistance of temperature sensor  702 . 
       FIG. 7C  illustrates an exemplary temperature sensor  702  according to examples of the disclosure. In some examples, temperature sensor  702  can have a zig-zag shape including a plurality of turns M. Temperature sensor  702  can have a trace width W, turn length L, and a space S between each turn M, for example. In some examples, temperature sensor  702  can be made of a conductive material, such as ITO. Other conductive materials are possible. 
       FIG. 7D  illustrates a table  730  of exemplary temperature sensor  702  dimensions according to examples of the disclosure. Table  730  includes exemplary dimensions for three temperature sensors  732 ,  734 , and  736 , for example. Temperature sensor  732  can have a trace width W of 4 micrometers, a turn spacing of 4 micrometers, a turn length L of 150 micrometers, and 20 turns M, for example. Temperature sensor  734  can have a trace width W of 8 micrometers, a turn spacing of 4 micrometers, a turn length L of 300 micrometers, and 20 turns M, for example. Temperature sensor  736  can have a trace width W of 12 micrometers, a turn spacing of 4 micrometers, a turn length L of 450 micrometers, and 20 turns M, for example. Additional or alternative dimensions are possible. In some examples, temperature sensors  732 ,  734 , and  736  can be coupled to sense circuitry (e.g., sense circuitry  700 ) and have a zig-zag shape similar to temperature sensor  702 . 
       FIG. 7E  illustrates an exemplary temperature sensor  702  with a plurality of connection points  740  according to examples of the disclosure. Connection points  740  can include input connection  741 , V+ connection  742 , a plurality of variable V− connections  743 ,  744 ,  745 , and  746  and GND connection  747 , for example. In some examples, variable V− connections  743 ,  744 ,  745 , and  746  can be at locations separated from V+ connection  742  by a plurality of the sensor&#39;s turns M. For example, variable V− connection  743  can be located at M=4, variable V− connection  744  can be located at M=10, variable V− connection  745  can be located at M=16, and variable V− connection  746  can be located at M=20. Accordingly, a voltage of the temperature sensor  702  can be measured across a selected number of turns M, as will be described below. 
     In some examples, connection points  740  can be used to couple temperature sensor  702  to sense circuitry  700 . For example, temperature sensor  702  can be coupled to current source  704  via input connection  741 . In some examples, the positive terminal of amplifier  706  can be coupled to V+ connection  742 . GND connection  747  can be used to couple the temperature sensor  702  to ground  710 , for example. In some examples, variable V− connections  743 ,  744 ,  745 , and  746  can be used to couple temperature sensor  702  to the negative terminal of amplifier  706  at one of several possible locations on the temperature sensor. 
     In some examples, measuring the voltage across a greater number of turns M of force sensor  702  can increase the output voltage at all temperatures. Likewise, in some examples, measuring the voltage across a lower number of turns M of force sensor  702  can decrease the output voltage at all temperatures. Therefore, a variable V− connection  743 ,  744 ,  745 , and  746  can be selected based on a number of factors including, but not limited to, the dynamic range of amplifier  706  and/or a desired signal to noise ratio (SNR) of the output voltage across temperature sensor  702  voltage. 
     Therefore, according to the above, some examples of the disclosure are directed to a temperature sensor comprising: a sense transistor coupled to readout circuitry; and a threshold voltage compensation circuit coupled to the sense transistor, wherein the threshold voltage compensation circuit is configured to compensate for a threshold voltage of the sense transistor. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the threshold voltage compensation circuit compensates for the threshold voltage of the sense transistor by pre-charging a gate electrode of the sense transistor to the threshold voltage of the sense transistor. Additionally or alternatively to one or more of the examples disclosed above, in some examples, compensating for the threshold voltage of the sense transistor comprises: coupling the gate electrode and the drain electrode of the transistor together, coupling the gate electrode and the drain electrode of the transistor to a reference voltage level, uncoupling the gate electrode and the drain electrode from the reference voltage level, maintaining coupling of the gate electrode and the drain electrode while a gate voltage at the gate electrode of the transistor discharges, and uncoupling the gate electrode and the drain electrode. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the readout circuitry is configured to apply a readout voltage to the sense transistor and sample an output current of the sense transistor. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the readout voltage is added to the gate voltage at the gate electrode after compensation for the threshold voltage of the sense transistor. 
     Some examples of the disclosure are directed to an apparatus comprising: a display panel comprising a plurality of display pixels, a plurality of temperature sensors disposed at different portions the display panel, wherein the plurality of temperature sensors comprise ratioed pairs of thin film transistors and the ratioed pairs of thin film transistors are formed on the display panel, and control circuitry for changing illumination properties of the plurality of display pixels based on changes is temperature detected by a proximate temperature sensor of the plurality of temperature sensors. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the control circuitry is further configured to: operate the plurality of temperature sensors in a first mode having a first power consumption level; determining whether a battery level of the apparatus falls below a threshold level; and in accordance with a determination that the power level has fallen below the threshold level, operate the plurality of temperature sensors in a second mode having a second power consumption level, lower than the first power level. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the second corresponds to operating the plurality of temperature sensors in a sub-threshold region of the ratioed pairs of thin firm transistors included in each respective temperature sensor. 
     Some examples of the disclosure are directed to a method comprising: operating temperature sensor proximate to a display pixel in a display in a first temperature sensing mode, determining whether a first characteristic of the temperature sensor is desired, and in accordance with a determination that the first characteristic of the temperature sensor is desired, switching to a second temperature sensing mode. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first temperature sensing mode is a high accuracy mode and the second temperature sensor is a low power consumption mode. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the lower power consumption mode comprises operating at least one transistor of the temperature sensor in a subthreshold current region. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the first characteristic is a reduced power consumption, and the determination of whether reduced power consumption is desired comprises comparing a battery power level of an electronic device including the display to a threshold battery power level. 
     Although examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the various examples as defined by the appended claims.

Metadata:
Filing Date: 20170809
Publication Date: 20191015
Grant Date: 20191015
Priority Date: 20160923
Inventors: ZHANG, SHENG
WANG, CHAOHAO
LO, CHEUK CHI
HUANG, CHUN-YAO
TANG, HOWARD
SACCHETTO, PAOLO
Assignee: APPLE INC
CPC Classifications: [{"code": "G01K7/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2330/021", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/2003", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3413", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01K7/01", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0693", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2330/023", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3648", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0242", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01K7/34", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2300/0426", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3413", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01K13/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3607", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3225", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/3225", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0426", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0251", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01K1/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2300/0452", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3648", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3607", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0693", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0426", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2310/0251", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2300/0452", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/2003", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G5/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G2330/021", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2330/023", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01K7/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/041", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/3413", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01K1/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3648", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01K7/34", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01K13/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2320/0242", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01K7/01", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3225", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/2003", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01K7/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01K1/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01K7/01", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G2330/021", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G2320/0666", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 61685592