Device temperature adjustment

Abstract

Systems associated with device temperature adjustment are described. A device temperature adjustment system can include an electronic device having a temperature sensor integrated therein to detect a temperature of the electronic device, and a temperature adjustment module coupled to the electronic device to adjust the temperature of the electronic device based on the detected temperature.

Description

Technical Field

[0001] This disclosure generally relates to equipment and methods associated with the temperature regulation of an apparatus. Background Technology

[0002] Memory resources are typically provided as internal semiconductor integrated circuits in computers or other electronic systems. Many different types of memory exist, including volatile and non-volatile memory. Volatile memory may require power to maintain its data (e.g., host data, erroneous data, etc.). Volatile memory can include random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), synchronous dynamic random access memory (SDRAM), and thyristor random access memory (TRAM), as well as other types. Non-volatile memory provides persistent data by retaining the stored data when no power is applied. Non-volatile memory can include NAND flash memory, NOR flash memory, and resistive variable memory, such as phase-change random access memory (PCRAM) and resistive random access memory (RRAM), ferroelectric random access memory (FeRAM), and magnetoresistive random access memory (MRAM) such as spin torque transfer random access memory (STT RAM), as well as other types.

[0003] Electronic systems typically include several processing resources (e.g., one or more processing resources) that can retrieve instructions from appropriate locations, execute instructions, and / or store the results of executed instructions in appropriate locations (e.g., memory resources). Processing resources may include several functional units, such as arithmetic logic unit (ALU) circuit systems, floating-point unit (FPU) circuit systems, and combinational logic blocks. These functional units can be used, for example, to execute instructions by performing logical operations such as AND, OR, NOT, NAND, NOR, and XOR, and inversion (e.g., NOT) logical operations on data (e.g., one or more operands). For example, the functional unit circuit system can be used to perform arithmetic operations on operands via several operations, such as addition, subtraction, multiplication, and division. Summary of the Invention

[0004] In one aspect, this disclosure provides a system comprising: an electronic device having an integrated temperature sensor for detecting a temperature of the electronic device; and a temperature adjustment module coupled to the electronic device for adjusting the temperature of the electronic device based on the detected temperature.

[0005] In another aspect, this disclosure further provides a system comprising: an electronic device having an integrated phase change material; and a temperature adjustment module configured to: sense the temperature of the electronic device; induce an endothermic reaction in the phase change material to reduce the temperature of the electronic device in response to the sensed temperature being higher than a specific temperature range; induce an exothermic reaction in the phase change material to increase the temperature of the electronic device in response to the sensed temperature being lower than a specific temperature range; and maintain the temperature in response to the sensed temperature being within the specific temperature range. Attached Figure Description

[0006] Figure 1 This is a functional diagram of a system comprising an electronic device communicating with a temperature adjustment module for device temperature adjustment, according to several embodiments of the present disclosure.

[0007] Figure 2 This is another functional diagram illustrating a system according to several embodiments of the present disclosure that includes an electronic device with a sensor and a phase change material (PCM) communicating with a temperature adjustment module for device temperature adjustment.

[0008] Figure 3 This is a flowchart illustrating an example method for adjusting device temperature according to several embodiments of the present disclosure.

[0009] Figure 4 This is another flowchart illustrating an example method for adjusting device temperature according to several embodiments of the present disclosure.

[0010] Figure 5 This is yet another flowchart illustrating an example method for adjusting device temperature according to several embodiments of the present disclosure.

[0011] Figure 6 This is a block diagram illustration of an example device according to several embodiments of the present disclosure. Detailed Implementation

[0012] Describe devices, systems, and methods related to device temperature regulation. Maintaining device performance under extreme temperatures can be challenging in electronic devices. For example, if the temperature of an electronic device exceeds its maximum permissible operating temperature, the memory device within the device may overheat, leading to overall device degradation and / or data loss. When the temperature of an electronic device approaches its lower limit, the memory device may face sudden shutdown problems and / or data loss. For example, memory devices in mobile phones and automotive GPS systems using DRAM or NAND memory may experience various extreme conditions during use (e.g., desert temperatures, frozen tundra temperatures, etc.) but may be difficult to regulate or may be unreliable under extreme conditions.

[0013] For example, in mobile devices, the temperature ranges for DRAM and NAND can be very wide (e.g., 100°C or higher), posing challenges to the design, cost, and performance of mobile devices. Performance can be suppressed to reduce the temperature of the mobile device, for example. Similar problems may occur in automotive equipment, which can have even wider temperature ranges (e.g., 150°C or higher). Other electronic devices can introduce similar challenges.

[0014] Examples of this disclosure can maintain the temperature of an electronic device (e.g., within a specific temperature range) through the implementation of thermal response devices. For example, phase change materials or photochromic materials can be used in the electronic device to adjust its temperature via endothermic, exothermic, or solar energy utilization. In some instances, this adjustment can be performed automatically, e.g., without user intervention. This automatic adjustment allows the electronic device to remain within a specific temperature range for optimal performance. In some instances, this allows for a more specific temperature range and improved performance of the electronic device. A narrower specific temperature range can increase design options by reducing design requirements and shorten development time, which can reduce time to market.

[0015] In some instances, embodiments of this disclosure may utilize existing temperature sensors of existing memory devices (e.g., NAND, DRAM, etc.) integrated into the memory device. For example, a NAND memory device may include components and / or sensors to determine its internal operating temperature, and the host may be able to configure the lower operating temperature and the upper operating temperature of the NAND device. This can be used by a temperature regulation module to determine when temperature adjustments should be made. For example, a DRAM device may also include sensors to determine its internal operating temperature.

[0016] Examples of this disclosure may include a system comprising: an electronic device having an integrated temperature sensor for detecting the temperature of the electronic device; and a temperature adjustment module coupled to the electronic device for adjusting the temperature of the electronic device based on the detected temperature. For example, phase change materials and / or photochromic materials may be used to adjust the temperature of the electronic device.

[0017] In the following detailed description of this disclosure, reference is made to the accompanying drawings, which form a part of this disclosure, and the drawings illustrate by way of illustration one or more embodiments of this disclosure. These embodiments are described in sufficient detail to enable those skilled in the art to practice embodiments of this disclosure, and it should be understood that other embodiments may be utilized and process, electrical, and structural changes may be made without departing from the scope of this disclosure.

[0018] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a / an” and “the” may include both singular and plural references. Furthermore, “a number,” “at least one,” and “one or more” (e.g., a number of memory devices) may refer to one or more memory devices, while “a number” is intended to mean more than one of such things. Additionally, the words “may” and “may” are used throughout this application in a permissive sense (i.e., possible, able) rather than in a mandatory sense (i.e., must). The term “comprising” and its derivatives mean “including but not limited to.” Depending on the context, the term “coupled / coupling” means a physical, direct or indirect connection or access to and movement (transmission) of commands and / or data.

[0019] The diagrams in this document follow a numbering rule, where the first one or more digits correspond to the diagram number, and the remaining digits identify elements or components within the diagram. Similar elements or components between different diagrams can be identified by using similar digits. For example, 104... Figure 1 The term "04" can refer to component "04", and similar components are found in... Figure 2 The symbol 204 may be used to refer to the element in the figure. As will be understood, elements shown in the various embodiments herein may be added, interchanged, and / or removed to provide several additional embodiments of this disclosure. Furthermore, the scale and / or relative dimensions of the elements provided in the figures are intended to illustrate certain embodiments of this disclosure and should not be construed as limiting.

[0020] Figure 1 This is a functional diagram of a system 100 including an electronic device 102 communicating with a temperature adjustment module 104 for device temperature adjustment, according to several embodiments of the present disclosure. For example, the electronic device 102 may include a DRAM device, a NAND memory device, or another electronic device, such as a mobile device including a memory device. The temperature adjustment module 104 may be a device having a control circuitry configured to determine whether the temperature of the associated electronic device 102 should be adjusted, and / or to adjust the temperature based on the determination. As used herein, "device" may refer to, but is not limited to, various structures or combinations thereof, such as circuits or circuit systems, dies or one or more dies, one or more devices, or one or more systems.

[0021] Electronic device 102 may have a temperature sensor integrated therein to detect the temperature of electronic device 102 (e.g., the internal temperature of a memory device), and temperature adjustment module 104 may be coupled to electronic device 102 to adjust the temperature of electronic device 102 based on the detected temperature. For example, electronic device 102 may include a PCM, and temperature adjustment module 104 may signal the PCM to adjust the temperature of electronic device 102. For example, the adjustment may include temperature adjustment module 104 inducing an exothermic reaction to increase the temperature of electronic device 102 in response to a detected temperature below a specific temperature range, or temperature adjustment module 104 inducing an endothermic reaction to decrease the temperature of electronic device 102 in response to a detected temperature above a specific temperature range. For example, the specific temperature range may include the stable temperature range of the PCM, the optimal operating temperature range of electronic device 102, or both.

[0022] For example, the temperature adjustment module 104 can adjust the temperature of the electronic device 102 across the entire circuit system. For example, the temperature of the electronic device 102 can be adjusted uniformly across the electronic device 102. For example, the temperature adjustment module 104 can be configured to adjust the temperature of an entire region of the circuitry of the electronic device 102, and not just the temperature of a portion of the device (e.g., not just a portion of a cellular structure).

[0023] In some instances, electronic device 102 may include a photochromic material, and the adjustment may include a temperature adjustment module 104 that uses the photochromic material to adjust the temperature of electronic device 102. For example, temperature adjustment module 104 may be configured to use solar energy to increase the temperature of electronic device 102 in response to a detected temperature below a certain temperature range, and to induce an endothermic reaction to decrease the temperature of electronic device 102 in response to a detected temperature above a certain temperature range. In some instances, system 100 may include a storage device to store the solar energy collected by the photochromic material and used to increase the temperature of electronic device 102.

[0024] Figure 2 This is another functional diagram illustrating a system 206 according to several embodiments of the present disclosure, comprising an electronic device 208 having a sensor 210 and a PCM 212 communicating with a temperature adjustment module 204 for device temperature adjustment. In some instances, system 206 may be similar to that relative to... Figure 1 The system 100 described.

[0025] System 206 may include electronic device 208, in which a temperature sensor 210 is integrated to detect the temperature of electronic device 208. Temperature sensor 210 may be an existing temperature sensor 210 of electronic device 208 or a newly integrated temperature sensor 210. PCM 212 may be integrated into the electronic device. Temperature adjustment module 204 may communicate with electronic device 208 and may use PCM 212 to raise the temperature of electronic device 208 in response to the temperature detected by temperature sensor 210 being below a specific temperature range. For example, PCM 212 may release heat to electronic device 208 via an exothermic reaction in response to the temperature being below a specific temperature range. This reduces the risk of sudden shutdown or data loss, for example, attributable to electronic device 208 reaching a lower temperature limit.

[0026] Temperature adjustment module 204 may use PCM 212 to reduce the temperature of electronic device 208 in response to temperature sensor 210 detecting a temperature higher than a specific temperature range. For example, PCM 212 may absorb heat from electronic device 208 via an endothermic reaction in response to a temperature higher than a specific temperature range. This reduces the risk of data loss or degradation of electronic device 208, for example, due to electronic device 208 reaching higher temperature limits. In some instances, temperature adjustment module 204 may maintain the temperature (e.g., without inducing either an endothermic or exothermic reaction) in response to temperature sensor 210 detecting a temperature within a specific temperature range.

[0027] In other words, temperature sensor 210 can detect temperatures within or outside a specific optimal operating temperature of electronic device 208. An electrical signal 214 can be sent to temperature regulation module 204, which determines whether the temperature of electronic device 208 should be lowered, raised, or maintained. Based on this determination, a temperature control signal 216 can be sent to electronic device 208, PCM 212, or both to adjust (e.g., induce an endothermic or exothermic reaction) or maintain the temperature of electronic device 208. In some examples, temperature regulation module 204 may be integrated into electronic device 208.

[0028] In some instances, electronic device 208 may be a NAND memory device or different electronic devices having a NAND memory device. Temperature sensor 210 may be integrated into the NAND memory device. In other instances, electronic device 208 may be a DRAM device or different electronic devices having a DRAM device. Temperature sensor 210 may be integrated into the DRAM device.

[0029] Although relative to Figure 2 PCM 212 is described, but in some instances, the electronic device may alternatively or additionally contain photochromic or other materials to raise or lower the temperature of the electronic device, as will be described herein with respect to Figure 5 Further description.

[0030] Figure 3 This is a flowchart 318 illustrating an example method for device temperature adjustment according to several embodiments of the present disclosure. Flowchart 318 shows a sensor 320 integrated into an electronic device and communicating with a temperature adjustment module 304. The sensor 320 and the temperature adjustment module 304 may be similar to... Figure 1 and 2 The sensor 210 and temperature adjustment modules 104 and 204 are shown.

[0031] At 322, the method includes sensor 320 determining whether the electronic device (e.g., internal temperature) is within a specific temperature range (e.g., "Range A"). This temperature range indicates the optimal performance range (e.g., optimal operating condition range) of the electronic device. If sensor 320 determines that the electronic device is within the specific temperature range, then no adjustment is made to the temperature of the electronic device, as described at 324. However, if the electronic device is determined to be outside the specific temperature range, then at 326 a determination is made (e.g., sensor indication) whether the determined temperature is above the upper limit of the specific temperature range, or at 328 a determination is made whether the determined temperature is below the lower limit of the specific temperature range.

[0032] If at 326 the determined temperature is found to be higher than the upper limit of a specific temperature range, the method continues to 330 where the temperature adjustment module 304 induces an endothermic reaction to reduce the temperature of the electronic device by absorbing heat from it. The temperature adjustment module 304 may induce the endothermic reaction, for example, by sending an electrical signal to the PCM on the electrical device to trigger a phase change, such as from "phase A" to "phase B".

[0033] If the determined temperature at 328 is found to be below the lower limit of a specific temperature range, the method continues until the temperature adjustment module 304 induces an exothermic reaction at 332 to raise the temperature of the electronic device by releasing heat to it. The temperature adjustment module 304 can induce an exothermic reaction, for example, by triggering a phase change, such as from "phase B" to "phase A," by sending an electrical signal to the PCM on the electrical device. The enthalpy of the phase change from phase A to phase B can be ΔH, where an endothermic reaction occurs when ΔH < 0, and an exothermic reaction occurs when ΔH > 0.

[0034] Figure 4 This is another flowchart 434 illustrating an example method for device temperature adjustment according to several embodiments of the present disclosure. Flowchart 434 illustrates an electronic device 436 communicating with a temperature adjustment module 404. The electronic device 436 and the temperature adjustment module 404 may be similar to... Figure 1 , 2The electronic devices 102, 208 and temperature adjustment modules 104, 204, 304 shown in Figure 3.

[0035] The method includes an electronic device 436 integrating a PCM therein, and a temperature regulation module 404 integrated into the system having the electronic device 436. The PCM can be integrated into the device and can remain stable within a specific temperature range. Figure 4 In the example shown, no temperature sensor is present. The method includes a temperature adjustment module 404 sensing the temperature of the electronic device 436 itself and introducing a phase change based on the determined temperature.

[0036] For example, the temperature adjustment module 404 can sense the temperature of the electronic device 436, and in response to the sensed temperature being higher than a certain temperature range, induce an endothermic reaction 430 in the PCM to reduce the temperature of the electronic device 436. The endothermic reaction 430 is induced by causing the PCM to change from a first state to a second state (e.g., from phase A to phase B) by a first applied signal.

[0037] Temperature adjustment module 404 can sense the temperature of electronic device 436 and, in response to the sensed temperature being below a specific temperature range, induce an exothermic reaction 432 in the PCM to increase the temperature of electronic device 436. The exothermic reaction 432 can be induced by causing the phase change material to change from a second state to a first state (e.g., from phase B to phase A) via a second applied signal. Temperature adjustment module 404 can maintain the temperature (e.g., neither inducing endothermic reaction 430 nor exothermic reaction 432) in response to the sensed temperature being within a specific temperature range.

[0038] Figure 5 This is another flowchart 538 illustrating an example method for device temperature adjustment according to several embodiments of the present disclosure. Flowchart 538 shows a sensor 540 integrated into an electronic device and communicating with a temperature adjustment module 504. The sensor 540 and the temperature adjustment module 504 may be similar to... Figures 1 to 4 The sensors 210, 320 and temperature adjustment modules 104, 204, 304, 404 are shown.

[0039] At 542, the method includes sensor 540 determining whether the electronic device (e.g., internal temperature) is within a specific temperature range (e.g., "Range A"). This temperature range indicates the optimal performance range (e.g., optimal operating condition range) of the electronic device. If sensor 540 determines that the electronic device is within the range, then no adjustment is made to the temperature of the electronic device, as shown at 544. However, if it is determined that the electronic device is outside the specific temperature range, then at 546 a determination is made (e.g., sensor indication) whether the determined temperature is above the upper limit of the specific temperature range, or at 548 a determination is made whether the determined temperature is below the lower limit of the specific temperature range.

[0040] If at 546 the determined temperature is found to be above the upper limit of a specific temperature range, the method continues to 550 where the temperature adjustment module 504 induces an endothermic reaction to reduce the temperature of the electronic device by absorbing heat from it. The temperature adjustment module 304 can induce an endothermic reaction, for example, by sending an electrical signal to a photochromic material on the electrical device to trigger a state change, such as from state "A" to state "B". The endothermic reaction can be triggered, for example, by photons.

[0041] If the determined temperature at 548 is below the lower limit of a specific temperature range, then at 552, the method continues to the temperature adjustment module 504, which directly uses solar energy to heat the electronic device. At 552, the temperature of the electronic device can be increased by releasing heat to the electronic device using the solar energy collected by the photochromic material. In some instances, the system including sensor 540 and / or temperature adjustment module 504 may include a storage device to store the solar energy collected by the photochromic material and used to increase the temperature of the electronic device. The enthalpy of the state change of the photochromic material from state A to state B may be ΔH, where an endothermic reaction occurs when ΔH < 0, and solar energy is used to heat the electronic device when ΔH > 0. When the electronic device is heated due to the direct use of solar energy, a phase or state change may not occur.

[0042] Figure 6 This is a block diagram illustration of an example device, such as an electronic memory system 601, according to several embodiments of the present disclosure. The memory system 601 includes devices, such as memory devices (e.g., electronic devices) 602; and a controller 660, such as a memory controller (e.g., a host controller). The controller 660 may include, for example, a processor. The controller 660 may be coupled to, for example, a host and may receive command signals (or commands), address signals (or addresses), and data signals (or data) from the host, and may output data to the host.

[0043] Memory device 602 includes a memory array 672 of memory cells. For example, memory array 672 may include one or more of the memory arrays of memory cells disclosed herein.

[0044] Memory device 602 includes address circuitry 668 to latch address signals provided via I / O connections 682 through I / O circuitry 680. Address signals can be received and decoded by row decoder 670 and column decoder 674 to access memory array 672. For example, row decoder 670 and / or column decoder 674 may include drivers.

[0045] Memory device 602 may use a sensing / buffer circuitry system to sense (e.g., read) data in memory array 672 by sensing voltage and / or current changes in the memory array columns. In some instances, the sensing / buffer circuitry system may be a read / latch circuitry system 676. The read / latch circuitry system 676 can read and latch data from memory array 672. An I / O circuitry system 680 is included for bidirectional data communication with controller 660 via I / O connection 682. A write circuitry system 678 is included for writing data to memory array 672.

[0046] The control circuitry 664 can decode signals provided from the controller 660 via the control connection 662. These signals may include chip signals, write enable signals, and address latch signals for controlling operations on the memory array 672, including data read and data write operations.

[0047] Control circuitry 664 may be included, for example, in controller 660. Controller 660 may include other circuitry, firmware, software, etc., individually or in combination. Controller 660 may be an external controller (e.g., in a die separate from memory array 672, whether fully or partially) or an internal controller (e.g., included in the same die as memory array 672). For example, an internal controller may be a state machine or a memory sequencer. In some instances, controller 660 may be configured such that memory device 602 and / or temperature regulation module perform at least the methods disclosed herein.

[0048] As used herein, the term “coupling” may include electrical coupling, direct coupling and / or direct connection without an intervening element (e.g., through direct physical contact), or indirect coupling and / or connection with an intervening element. The term coupling may further include two or more elements that cooperate or interact with each other (e.g., in a causal relationship).

[0049] Those skilled in the art will understand that additional circuitry and signals can be provided, and that simplification has been achieved. Figure 6The memory system 601. It should be recognized that, reference Figure 6 The functionality of the various block components described need not be separated from the different components or component portions of the integrated circuit device. For example, a single component or component portion of the integrated circuit device may be adapted to perform... Figure 6 The functionality of more than one block component. Alternatively, one or more components or component portions of an integrated circuit device can be combined to perform... Figure 6 The functionality of a single block component.

[0050] While specific embodiments have been shown and described herein, those skilled in the art will understand that arrangements calculated to achieve the same results may replace the specific embodiments shown. This disclosure is intended to cover modifications or variations of one or more embodiments of this disclosure. It should be understood that the above description has been carried out illustratively and not restrictively. Combinations of the above embodiments and other embodiments not specifically described herein will be apparent to those skilled in the art upon review of the above description. The scope of one or more embodiments of this disclosure includes other applications in which the above structures and processes are used. Therefore, the scope of one or more embodiments of this disclosure should be determined with reference to the appended claims together with the full scope of the equivalents given by such claims.

[0051] In the foregoing detailed embodiments, some features are grouped together in a single embodiment for the purpose of simplification. This approach of the present disclosure should not be construed as reflecting an intention that the disclosed embodiments must use more features than expressly stated in each claim. In fact, as reflected in the appended claims, the subject matter of the invention lies in less than all the features of a single disclosed embodiment. Therefore, the appended claims are hereby incorporated into the detailed embodiments, wherein each claim is, in itself, a separate embodiment.

Claims

1. An electronic system (100) comprising: Electronic devices (102, 208, 436) integrating temperature sensors (210, 320, 540) for detecting the temperature of the electronic devices, wherein the electronic devices include a phase change material (212); and Temperature adjustment modules (104, 204, 304, 404, 504) are coupled to the electronic device to signal the phase change material to adjust the temperature of the electronic device based on the detected temperature. The temperature adjustment module, in response to the detected temperature being below a specific temperature range (328), induces an exothermic reaction (332, 432) to increase the temperature of the electronic device; and The temperature adjustment module, in response to the detected temperature being higher than a specific temperature range (326), induces an endothermic reaction (330, 430) to reduce the temperature of the electronic device.

2. The electronic system according to claim 1, wherein when the detected temperature is outside the specific temperature range (322, 542), the temperature sensor sends an electrical signal (214) to the temperature adjustment module.

3. The electronic system of claim 2, wherein the specific temperature range includes the optimal operating temperature range of the electronic device.

4. The electronic system according to any one of claims 1 to 2, wherein the temperature adjustment module is used to adjust the temperature of the electronic device across the entire circuitry of the electronic device.

5. The electronic system according to any one of claims 1 to 2, wherein the electronic device comprises a photochromic material, and the temperature adjustment module uses the photochromic material to adjust the temperature.

6. The electronic system of claim 5, further comprising a storage device for storing solar energy collected by the photochromic material and used to increase the temperature of the electronic device.

7. The electronic system according to any one of claims 1 to 2, wherein the electronic device is a dynamic random access memory (DRAM) device, and the temperature sensor is a temperature sensor integrated into the DRAM device.

8. The electronic system according to any one of claims 1 to 2, wherein the electronic device is a NAND device, and the temperature sensor is a temperature sensor integrated into the NAND device.

9. The electronic system according to any one of claims 1 to 2, wherein the temperature adjustment module is integrated into the electronic device.

10. An electronic system (100, 206) comprising: Electronic devices (102, 208, 436) that integrate phase change materials (212); as well as Temperature adjustment modules (104, 204, 304, 404, 504), configured as follows: Sensing the temperature of the electronic device; In response to the sensed temperature being higher than a specific temperature range (326), an endothermic reaction (330, 430) is induced in the phase change material to reduce the temperature of the electronic device; In response to the sensed temperature being below a specific temperature range (328), an exothermic reaction (332, 432) is induced in the phase change material to increase the temperature of the electronic device; and In response to the sensed temperature being within the specific temperature range (324), the temperature is maintained.

11. The electronic system of claim 10, wherein the specific temperature range includes: The stable temperature range of the phase change material; The optimal operating temperature range of the electronic device; or Both of these.

12. The electronic system of claim 10, wherein the temperature adjustment module is configured to send a signal (216) to the electronic device, the phase change material, or both, to induce the endothermic reaction or the exothermic reaction.

13. The electronic system according to claim 10, wherein: The endothermic reaction (430) is induced by causing the phase change material to change from a first state to a second state through a first applied signal; and The exothermic reaction (432) is caused by the second applied signal causing the phase change material to change from the second state to the first state.

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