ELECTRONIC DEVICE AND METHOD FOR DETERMINING THE TEMPERATURE OF AN ELECTRONIC DEVICE

Abstract

An electronic device (100, 400), comprising: A first frequency source (108, 401) set up to generate a first oscillation signal, the deviation of which from a nominal frequency of the first frequency source (108, 401) is temperature-dependent, wherein the frequency deviation is the same for a plurality of temperatures lying in different temperature ranges of a plurality of temperature ranges; A processing circuit (402), configured to Determining the temperature range from the plurality of temperature ranges of the electronic device (100, 400) in which a temperature of the electronic device (100, 400) lies, by Determining the temperature range by estimating the frequency deviation of a second oscillation signal generated by a second frequency source (109) from a nominal frequency of the second frequency source (109) and / or determining the temperature range using a temperature sensor (107) of the electronic device (100, 400); and Determining the temperature of the electronic device (100, 400) from an estimate of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source (108, 401) taking into account the determined temperature range.

Description

[0001] The present disclosure relates to electronic devices and methods for determining the temperature of an electronic device.

[0002] Components of electronic devices typically have a temperature range within which they operate reliably. Especially in applications with high safety requirements, such as in a vehicle, it is crucial to detect when a current temperature falls outside this range in order to react accordingly, i.e., to trigger appropriate safety measures. Therefore, the temperature of components within an electronic device must be determined, which, at least for components that do not generate much heat themselves, should be approximately equal to the ambient temperature of the electronic device. Since temperature sensors, particularly accurate ones, incur additional costs, approaches that allow for an accurate determination of the ambient temperature with minimal additional component requirements are desirable.

[0003] Document US 2020 / 0 056 946 A1 describes a temperature sensing device in which a thermal detection signal is provided at a first clock frequency, and an electronic signal based on a second clock frequency lower than the first is received by a device. The time interval between the timing of the thermal detection signal and the electronic signal is measured, and a temperature is determined from an analysis of the measured time intervals based on the knowledge of the frequency-temperature characteristics of the electronic signal.

[0004] Document US 2019 / 0 056 274 A1 describes a temperature sensor comprising a first oscillator configured to generate a first oscillating signal with a first frequency that varies with a detected temperature and a reference parameter; a second oscillator configured to generate a second oscillating signal with a second frequency that varies with the reference parameter; and a time-to-digital converter configured to generate a digital output indicating the detected temperature based on the ratio of the first frequency to the second frequency. Because the first and second frequencies depend on the reference parameter, fluctuations in the reference parameter cancel each other out.

[0005] In publication US 2002 / 0 150 141 A1, a temperature sensor is described in which, based on the frequency of one oscillator, frequencies of one or more other oscillators are measured and frequency-temperature characteristics of several oscillator circuits are synthesized to create an accurate temperature sensor.

[0006] The publication JP S55 - 138 626 A describes a high-precision time-temperature control with low power consumption by providing two quartz oscillators with similar frequency-temperature characteristics, so that the frequency differences of the two oscillators form a linear function in an operating temperature range.

[0007] According to various embodiments, an electronic device is provided which includes a first frequency source configured to generate a first oscillation signal whose deviation from a nominal frequency of the first frequency source depends on the temperature, wherein the frequency deviation is the same for a plurality of temperatures lying in different temperature ranges of a plurality of temperature ranges, and a processing circuit configured to determine the temperature range of the plurality of temperature ranges of the electronic device in which a temperature of the electronic device lies by at least one of determining the temperature range by means of an estimate of the frequency deviation of a secondto determine the temperature range of the electronic device from an oscillation signal generated by a second frequency source, based on a nominal frequency of the second frequency source and by determining the temperature range using a temperature sensor, and to determine the temperature of the electronic device from an estimate of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source, taking into account the determined temperature range.

[0008] In the drawings, similar reference numerals generally refer to the same parts in the different views. The drawings are not necessarily to scale but generally illustrate the principles of the invention. The following description details various aspects with reference to the following drawings, in which: Fig. Figure 1 shows an electronic device. Fig. Figure 2 shows a frequency deviation-temperature diagram. Fig. Figure 3 illustrates the application of the above approach to determining the ambient temperature during the life cycle of an electronic control unit (ECU). Fig. Figure 4 shows an electronic device according to one embodiment.

[0009] The following detailed description refers to the accompanying drawings, which illustrate specific details and aspects of this disclosure in which the invention can be implemented. Other aspects may be used, and structural, logical, and electrical modifications may be made without departing from the scope of the invention. The various aspects of this disclosure are not necessarily mutually exclusive, as some aspects of this disclosure may be combined with one or more other aspects of this disclosure to form new aspects.

[0010] Fig. Figure 1 shows an electronic device 100.

[0011] The electronic device 100 is, for example, an electronic control unit (ECU), especially for a vehicle, but can also be a control device or a data processing device for other devices such as machines, generators, etc.

[0012] The electronic device 100 contains a circuit board 101 on which components, including an integrated circuit (chip), in particular a microcontroller 102, and further components 103, 104, 105, are mounted. The further components may be analog or digital (possibly integrated) circuits such as interface circuits, power supply circuits, converters, etc.

[0013] The electronic device 100 has an ambient temperature T a, which (at least to a negligible extent) is equal to the temperature of the circuit board 101 and the other components 103, 104, 105, while the microcontroller 102, as a larger component that generates a relatively large amount of heat, has an internal temperature that differs from the ambient temperature T a its junction temperature T can vary j .

[0014] The components typically have a safe temperature range, within which they can be assumed to operate reliably. For example, it can be assumed that the other components will function normally within a safe temperature range of -40°C to 125°C. If the ambient temperature T aOutside this range, an alarm may be triggered, for example in an application (such as a control unit for a vehicle) where safety requirements exist and it must be ensured that the components function reliably.

[0015] To determine whether the temperature of the other components 103, 104, 105, which are equal to the ambient temperature T a Assuming it is within its safe temperature range, the ambient temperature T must be a to be measured. For this purpose, an ambient temperature sensor 106 can be provided on the circuit board 101, which is used to measure the ambient temperature T. ais set up. It can, for example, supply measurement data to the microcontroller 102 (or a signal that the temperature measurement has failed), and the microcontroller 102 can react accordingly, e.g. trigger an alarm signal if the measured temperature is outside the safe temperature range, which in turn triggers safety measures, such as the activation of a cooling system 112 in the event that the measured temperature is above the safe temperature range.

[0016] According to this functionality, the ambient temperature sensor 106 should be highly accurate at certain points, namely at the endpoints of the safe temperature range (e.g., -40°C and 125°C), to enable accurate detection of over- and under-temperature. For other temperature ranges, standard accuracy may suffice. Furthermore, depending on the application, the ambient temperature sensor 106 may need to meet safety requirements such as ASIL-D. Consequently, the ambient temperature sensor 106 can be relatively expensive, and approaches to avoid this need are desirable.

[0017] One approach is to measure the junction temperature T measured by a die temperature sensor (DTS) 107, i.e., an internal temperature sensor of the microcontroller 102. j also as an estimate for the ambient temperature T ato use. Since a die temperature sensor (DTS) 107 is usually already present in a microcontroller (to ensure its correct operation), no additional sensor is required. However, as mentioned earlier, in applications with high safety requirements, it must be ensured that an alarm is reliably triggered when the ambient temperature T exceeds a certain threshold. a falls outside the safe temperature range of the other components 103, 104, 105. The problem is that the ambient temperature T a from the barrier temperature T jThe operating temperature of microcontroller 102 may differ, for example, because microcontroller 102 heats up more during operation than the other components 103, 104, 105, or because it has a heatsink while the other components 103, 104, 105 do not. This problem can be addressed by using a smaller safe temperature range for triggering an alarm than the actual safe temperature range. While the actual safe temperature range, as in the example above, is between -40°C and 125°C, microcontroller 102 can, for example, be configured to trigger an alarm (and activate safety measures) when its junction temperature T exceeds a certain threshold. jnot between -37°C and 122°C. This prevents an alarm from being triggered due to the difference between the ambient temperature range and the junction temperature range of microcontroller 102, because the junction temperature T is not within the specified range. j within the safe temperature range, although the ambient temperature T a not within the safe temperature range of the other components 103, 104, 105. On the other hand, this restricts the temperature range in which the electronic device 100 can be operated, since an alarm may be triggered even though the ambient temperature T a within the safe temperature range.

[0018] Therefore, according to various embodiments, a frequency source 108, which is located outside the microcontroller 102, is used as the basis for determining the ambient temperature T. a used.

[0019] In this example, frequency source 108 provides a clock frequency for a real-time clock (RTC), which allows microcontroller 102 to determine the current time (i.e., seconds, minutes, etc.; this can be relevant for obtaining timestamps for events, etc.). It is a crystal, or contains a crystal, and is therefore referred to as the RTC crystal in the following. For example, it could be a tuning fork crystal.

[0020] The frequency emitted by a crystal is generally temperature-dependent. Accordingly, the frequency supplied by frequency source 108 can be used by microcontroller 102 to obtain information about the ambient temperature T. a to win.

[0021] Fig. Figure 2 shows a frequency deviation-temperature diagram for 200.

[0022] Diagram 200 contains, in particular, a first curve 201, which indicates the frequency deviation from a nominal frequency in ppm of an RTC crystal as a function of temperature. The temperature scale (x-axis) is designed so that the temperature increases from left to right from -40° to 120°C, while the frequency deviation scale (y-axis) is designed so that the frequency deviation increases from bottom to top from -350 ppm to 50 ppm.

[0023] As can be seen, the dependence of the frequency deviation on the temperature of the RTC crystal has the form of an inverted parabola. Accordingly, for most points (except those exactly at the vertex of the parabola (in this example at approximately 30°C)), there is ambiguity: If the microcontroller 102 detects a certain frequency deviation of the RTC crystal frequency from the nominal RTC crystal frequency, two temperatures can cause this frequency deviation: the temperature range of the left branch of the inverted parabola (in this example from -40°C to approximately 30°C) and the temperature range of the right branch of the inverted parabola (in this example from approximately 30°C to 120°C).

[0024] According to various embodiments, the microcontroller 102 is configured to resolve this ambiguity by using one (or possibly even both) of: 1) Use of the internal (junction) temperature sensor 107 to decide whether the ambient temperature T a within the temperature range of the left leg of the inverted parabola or within the temperature range of the right leg of the inverted parabola. It should be noted that, as explained above, the internal temperature sensor 107 is not (alone) suitable for measuring the ambient temperature T. a to deduce, its temperature measurement usually allows the microcontroller 102 to decide whether the ambient temperature T a within the temperature range of the left leg of the inverted parabola or within the temperature range of the right leg of the inverted parabola. 2) Use of the frequency deviation from another (i.e. second) frequency source 109, whose frequency deviation dependence on temperature is different from that of the frequency source 108 (hereinafter referred to as the first frequency source for clarity).

[0025] The second frequency source 109 provides a clock frequency (e.g., the CPU clock frequency, i.e., the clock that defines the CPU's processing cycles) for the microcontroller 102 in this example. It is or contains a crystal, which is therefore referred to as the main crystal in the following. It could, for example, be an AT-cut MHz crystal.

[0026] Diagram 200 contains a second curve 202, which indicates the frequency deviation from a nominal frequency in ppm of a main crystal as a function of temperature.

[0027] As can be seen, the dependence of the frequency deviation on the temperature of the main crystal is such that there is no ambiguity, at least within a certain range that can be used to determine the direction of the temperature change. However, the dependence of the frequency deviation of the main crystal is much flatter than that of the RTC crystal and therefore only allows a relatively rough estimate of the ambient temperature T. a However, if the microcontroller 102 detects a certain frequency deviation of the main crystal from the nominal frequency of the main crystal, it can, based on the rough estimate of the frequency deviation of the main crystal, unambiguously determine whether the ambient temperature T aThe microcontroller 102 can then use the dependence of the RTC crystal frequency deviation on the temperature, as determined by the parabolic branch, to accurately measure the ambient temperature T. a to obtain.

[0028] It should be noted that determining the absolute frequency deviation of a single crystal can be difficult. In this case, to measure the frequency deviation of the RTC crystal (which is highly temperature-dependent), its frequency can be compared with the frequency of a crystal (e.g., the main crystal, i.e., the second curve 202) whose frequency is much more stable. The result of such a comparison is a third curve 203, which is similar to the first curve 201 and can therefore be considered an estimate of the first curve 201. When the first curve 201 is referenced below, it refers to the third curve 203 (which differs from the "true" curve because the reference used for its determination is itself temperature-dependent).It should be noted that if the frequency deviation of the main crystal is used to resolve the ambiguity (see point 2) above), a third frequency source can be used as a reference to estimate the frequency deviation of the RTC crystal and to estimate the frequency deviation of the main crystal.

[0029] It is evident that the second frequency source 109 must exhibit a different dependence of the frequency deviation on temperature than the first frequency source 108 in order to resolve the ambiguity. For crystal-based frequency sources, this can be achieved by using frequency sources with different crystals, i.e., crystals with different properties, e.g., with different cuts (AT, BT, CT, SC...).

[0030] The microcontroller 102 can use a frequency-to-digital converter 110 (i.e., a circuit configured to generate a digital value indicating the frequency of an input signal) to determine the frequency deviation of the respective frequency source 108, 109. Such a frequency-to-digital converter 110 can be implemented to measure frequency deviations of < 1 ppm within 10 ms.

[0031] It should be noted that the approach described above for determining the ambient temperature T a does not depend on the supply voltage or the semiconductor process used for the microcontroller 102.

[0032] Fig. Figure 3 illustrates the application of the above approach to determining the ambient temperature T. a in the life cycle of an ECU.

[0033] In 301, the frequency deviation of the frequency sources 108, 109 is measured at different temperatures (which corresponds, for example, to the points in the diagram of the Fig. 2). This information is written to a non-volatile memory 111 of the ECU 100 (which may also be internal to the microcontroller 102). This can include, in particular, the frequency deviations at the endpoints of the safe temperature range (i.e., threshold values).

[0034] In 302, a cooling system 112 can be set up for the additional components 103, 104, and 105. The design of the cooling system 112 typically depends on the thermal resistance of the respective chip package. If both an ambient temperature sensor and a chip temperature sensor are present, the realistic thermal resistance can be determined by Rth = (T j _T a ) / W can be derived, where W is the power loss of the device. The cooling system 112 can then be configured accordingly.

[0035] In the field, i.e., in normal operation, the microcontroller 102 can decide, using the internal temperature sensor 107 of the microcontroller 102 or the main crystal in 303, whether the ambient temperature T a in the temperature range of the left leg of the parabola or in the temperature range of the right leg of the parabola, as described above.

[0036] He can then set the ambient temperature T in 304. a accurately determine the frequency deviation from the temperature of the RTC clock crystal and trigger an alarm when the determined ambient temperature T is exceeded. a is outside the safe ambient temperature range.

[0037] To increase safety, an additional ambient temperature sensor 106 can be provided and used for measurement in 305. Safety requirements such as ASIL-D can then be achieved, for example, by also measuring the ambient temperature T. ais estimated from the DTS (taking into account a predetermined thermal resistance between the microcontroller 102 and the ambient temperature sensor 106).

[0038] Using multiple measurement points, a curve (e.g., an inverted parabola) can be fitted to determine the dependence of the frequency deviation on the ambient temperature T. a to determine.

[0039] Optionally, the frequency deviation of a crystal at a fixed temperature during operation can be measured in 306, and if it differs from the information stored in the NVM 111, the information can be updated or a corresponding offset can be stored in the NVM 111.

[0040] In summary, according to various embodiments, an electronic device is provided as described in Fig. 4 illustrates.

[0041] Fig. Figure 4 shows an electronic device 400 according to one embodiment.

[0042] The electronic device 400 includes a first frequency source 401, which is configured to generate a first oscillation signal whose deviation from a nominal frequency of the first frequency source 401 is temperature-dependent, wherein the frequency deviation is the same for a plurality of temperatures lying in different temperature ranges of a plurality of temperature ranges (i.e., there are several temperatures for which the frequency deviation is the same, and any two of these several temperatures are not in the same temperature range, as in the example above with the two parabolic branches; in other words, the mapping from temperature to frequency deviation is not injective).

[0043] The electronic device 400 further includes a processing circuit 402, which is configured to • Determining the temperature range from the plurality of temperature ranges of the electronic device in which a temperature of the electronic device lies, by at least one of ◯ Determining the temperature range from an estimate of a frequency deviation of a second oscillation signal generated by a second frequency source from a nominal frequency of the second frequency source (hereinafter referred to as the first option) and • Determining the temperature range using a temperature sensor of the electronic device (hereinafter referred to as the second option); and • Determining the temperature of the electronic device from an estimate of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source 401, taking into account the determined temperature range.

[0044] The electronic device 400 can contain the second frequency source, the temperature sensor, or both.

[0045] In other words, according to various embodiments, the ambiguity of a frequency source with respect to temperature, which leads to a current frequency deviation, is resolved by a second frequency source or a temperature sensor (or possibly both, e.g. to have redundancy).

[0046] In the first option, the estimated frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source 401 and the estimated frequency deviation of the second oscillation signal from the nominal frequency of the second frequency source are determined, for example, by using a third (sufficiently stable) frequency source as a reference (by comparing the frequency of the first or second frequency source with the frequency of the third frequency source - if necessary by splitting one of the frequencies to be compared to make the frequencies comparable).

[0047] In the second option, the estimation of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source 401 can also be determined by a comparison with the oscillation signal supplied by the second frequency source.

[0048] The approach in Fig. Section 4 makes it possible to avoid the need for an ambient temperature sensor 106 in an electronic device (on the circuit board) by reusing components that are required anyway, such as an RTC frequency source. To eliminate the ambiguity, one possibility is to use an internal DTS to decide on the temperature range (the thermal resistance between the microcontroller and the circuit board can be taken into account in this case), and the other possibility is to reuse a main frequency source in addition to the RTC frequency source (both of which may also be present in the electronic circuit).

[0049] In particular, the ambient temperature sensor 106 can be omitted, and the microcontroller pins that were previously used to connect the temperature sensor can be used for other functions.

[0050] It should be noted that for better system integration, a MEMS (Micro-Electro-Mechanical System) device or a ceramic resonator (instead of a crystal-based oscillator) can be used as one or both frequency sources. Here too, the frequency is temperature-dependent. Therefore, the first frequency source 401 can be a first oscillator of any of these types, and the second frequency source can be a second oscillator of any of these types.

[0051] The in Fig. The approach shown in section 4 can be used, for example, to meet the ASIL-D safety requirements.

[0052] A realistic thermal resistance can be used instead of a "worst-case" thermal resistance, thereby reducing the bill of materials costs for temperature management compared to the "worst-case" approach.

[0053] The following are several examples: Example 1 is an electronic device such as that found in Fig. 4 is illustrated. Example 2 is an electronic device according to Example 1, comprising a circuit board and a chip with a central processing unit, wherein the temperature of the electronic device is a temperature of the circuit board and the temperature sensor of the electronic device is a temperature sensor configured to measure an internal temperature of the chip. Example 3 is an electronic device according to Example 2, comprising a circuit board and a chip with a central processing unit, wherein the chip is configured to generate the clock signal of the central processing unit using the second oscillation signal. Example 4 is an electronic device according to any of Examples 1 to 3, wherein the deviation of the frequency of the first oscillation signal from the nominal frequency of the first frequency source and the deviation of the frequency of the second oscillation signal from the nominal frequency of the second frequency source depend differently on the temperature. Example 5 is an electronic device according to any of Examples 1 to 4, wherein the deviation of the frequency of the second oscillation signal from the nominal frequency of the second frequency source is different for all temperatures in the majority of the temperature ranges. Example 6 is an electronic device according to any of Examples 1 to 5, wherein the first frequency source is set up to generate the first oscillation signal using a first crystal and the second frequency source is set up to generate the second oscillation signal using a second crystal. Example 7 is an electronic device according to Example 6, in which the first crystal and the second crystal have different properties. Example 8 is an electronic device according to Example 7, in which the first crystal and the second crystal have different cuts. Example 9 is an electronic device according to any of Examples 1 to 8, which includes a real-time clock configured to determine a time using the first oscillation signal. Example 10 is an electronic device according to any of Examples 1 to 9, which includes a memory configured to store information about the temperature dependence of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source. Example 11 is an electronic device according to Example 10, configured to update the information on the temperature dependence of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source in memory based on frequency measurements at predetermined temperatures. Example 12 is an electronic device according to Example 10 or 11, wherein the memory is configured to store information about the temperature dependence of the frequency deviation of the second oscillation signal from the nominal frequency of the second frequency source. Example 13 is an electronic device according to Example 12, configured to update the information on the temperature dependence of the frequency deviation of the second oscillation signal from the nominal frequency of the second frequency source in memory based on frequency measurements at predetermined temperatures. Example 14 is a method for determining the temperature of an electronic device, comprising generating a first oscillation signal by a first frequency source, the deviation of which from a nominal frequency of the first frequency source is temperature-dependent, wherein the frequency deviation is the same for a plurality of temperatures lying in different temperature ranges of a plurality of temperature ranges, and determining the temperature range of the plurality of temperature ranges of the electronic device in which a temperature of the electronic device lies by at least one of • Determining the temperature range based on an estimate of the frequency deviation of a second oscillation signal generated by a second frequency source from a nominal frequency of the second frequency source and • Determining the temperature range using a temperature sensor of the electronic device; and

[0054] Determining the temperature of the electronic device from an estimate of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source, taking into account the determined temperature range.

[0055] Although specific embodiments have been illustrated and described herein, the person skilled in the art will recognize that a multitude of alternative and / or equivalent implementations can be used instead of the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to extend to any adaptations or variations of the specific embodiments described herein. Therefore, it is intended that this invention be limited only by the claims and their equivalents.

[0056] Reference sign 100 Electronic Device 101 circuit board 102 microcontrollers 103-105 Other components 106 Ambient temperature sensor 107 Die temperature sensor 108 First frequency source 109 Second frequency source 110 Frequency-to-Digital Converters 111 Non-volatile storage 112 Cooling system 201, 202 Frequency deviation curves 301-306 operations 400 Electronic device 401 Frequency source 402 Processing circuit

Claims

[1] An electronic device (100, 400) comprising: A first frequency source (108, 401) set up to generate a first oscillation signal, the deviation of which from a nominal frequency of the first frequency source (108, 401) is temperature-dependent, wherein the frequency deviation is the same for a plurality of temperatures lying in different temperature ranges of a plurality of temperature ranges; A processing circuit (402), configured to Determining the temperature range from the plurality of temperature ranges of the electronic device (100, 400) in which a temperature of the electronic device (100, 400) lies, by Determining the temperature range by estimating the frequency deviation of a second oscillation signal generated by a second frequency source (109) from a nominal frequency of the second frequency source (109) and / or determining the temperature range using a temperature sensor (107) of the electronic device (100, 400); and Determining the temperature of the electronic device (100, 400) from an estimate of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source (108, 401) taking into account the determined temperature range. [2] The electronic device (100, 400) according to claim 1, comprising a circuit board and a chip with a central processing unit, wherein the temperature of the electronic device (100, 400) is a temperature of the circuit board and the temperature sensor (107) of the electronic device (100, 400) is a temperature sensor (107) configured to measure an internal temperature of the chip. [3] The electronic device (100, 400) according to claim 2, comprising a circuit board and a chip with a central processing unit, wherein the chip is configured to generate the clock of the central processing unit using the second oscillation signal. [4] The electronic device (100, 400) according to any one of claims 1 to 3, wherein the deviation of the frequency of the first oscillation signal from the nominal frequency of the first frequency source (108, 401) and the deviation of the frequency of the second oscillation signal from the nominal frequency of the second frequency source (109) depend differently on the temperature. [5] The electronic device (100, 400) according to any one of claims 1 to 4, wherein the deviation of the frequency of the second oscillation signal from the nominal frequency of the second frequency source (109) is different for all temperatures in the majority of the temperature ranges. [6] The electronic device (100, 400) according to any one of claims 1 to 5, wherein the first frequency source (108, 401) is configured to generate the first oscillation signal using a first crystal and the second frequency source (109) is configured to generate the second oscillation signal using a second crystal. [7] The electronic device (100, 400) according to claim 6, wherein the first crystal and the second crystal have different properties. [8] The electronic device (100, 400) according to claim 7, wherein the first and the second crystal have different cuts. [9] The electronic device (100, 400) according to any one of claims 1 to 8, comprising a real-time clock configured to determine a time using the first oscillation signal. [10] The electronic device (100, 400) according to any one of claims 1 to 9, comprising a memory configured to store information about the temperature dependence of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source (108, 401). [11] The electronic device (100, 400) according to claim 10, configured to update the information about the temperature dependence of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source (108, 401) in memory based on frequency measurements at predetermined temperatures. [12] The electronic device (100, 400) according to claim 10 or 11, wherein the memory is configured to store information about the temperature dependence of the frequency deviation of the second oscillation signal from the nominal frequency of the second frequency source (109). [13] The electronic device (100, 400) according to claim 12, configured to update the information about the temperature dependence of the frequency deviation of the second oscillation signal from the nominal frequency of the second frequency source (109) in the memory based on frequency measurements at predetermined temperatures. [14] A method for determining the temperature of an electronic device (100, 400), comprising: Generating a first oscillation signal by a first frequency source (108, 401) whose deviation from a nominal frequency of the first frequency source (108, 401) is temperature-dependent, wherein the frequency deviation is the same for a plurality of temperatures lying in different temperature ranges of a plurality of temperature ranges; Determining the temperature range of the plurality of temperature ranges of the electronic device (100, 400) in which a temperature of the electronic device (100, 400) lies, by Determining the temperature range by estimating the frequency deviation of a second oscillation signal generated by a second frequency source (109) from a nominal frequency of the second frequency source (109) and / or determining the temperature range using a temperature sensor (107) of the electronic device (100, 400); and Determining the temperature of the electronic device (100, 400) from an estimate of the frequency deviation of the first oscillation signal from the nominal frequency of the first frequency source (108, 401) taking into account the determined temperature range.

Images