EP0323466A1 - Circuit compensateur a oscillateur a cristal - Google Patents

Circuit compensateur a oscillateur a cristal

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Publication number
EP0323466A1
EP0323466A1 EP87905586A EP87905586A EP0323466A1 EP 0323466 A1 EP0323466 A1 EP 0323466A1 EP 87905586 A EP87905586 A EP 87905586A EP 87905586 A EP87905586 A EP 87905586A EP 0323466 A1 EP0323466 A1 EP 0323466A1
Authority
EP
European Patent Office
Prior art keywords
circuit
temperature
oscillator
crystal
frequency
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP87905586A
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German (de)
English (en)
Inventor
Franz Leitl
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0323466A1 publication Critical patent/EP0323466A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L1/00—Stabilisation of generator output against variations of physical values, e.g. power supply
    • H03L1/02—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only
    • H03L1/022—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature
    • H03L1/023—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature by using voltage variable capacitance diodes
    • H03L1/025—Stabilisation of generator output against variations of physical values, e.g. power supply against variations of temperature only by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature by using voltage variable capacitance diodes and a memory for digitally storing correction values

Definitions

  • the invention relates to a crystal oscillator compensation circuit with an oscillator crystal, hereinafter called crystal, which is excited to oscillate by a crystal oscillator circuit, and an adjustable capacitance for adjusting the frequency of the oscillator.
  • Oscillator crystals are piezoelectric crystals, usually quartz crystals. They are mostly cuboid platelets that are cut out of a crystal in a certain direction. These plates are provided with electrodes on two opposite surfaces, to which an alternating voltage is supplied. If the exciting frequency corresponds to the resonance frequency or the anti-resonance frequency of the crystal, it vibrates with a large amplitude, which in turn is used to stabilize the frequency of the oscillator circuit. The frequency of the crystal can be changed within certain limits with the aid of a component with an adjustable reactive reactance, usually a capacitance diode.
  • a crystal vibrates at a certain frequency due to given dimensions, a given cutting direction and a given control voltage at the capacitance diode, then this frequency is only kept for a certain temperature and only for a certain time. If the temperature changes, the frequency also changes. Frequency changes also occur with advancing time.
  • the time-dependent behavior of the frequency is kept as small as possible by using crystals that are used at elevated temperatures, e.g. B. 80-90 degrees Celsius for some time, e.g. B. have been aged for a few months. After such treatment, the Kri stal 1 properties change little over time.
  • the temperature dependence of the frequency is attempted to be compensated for by the crystal being operated in series and / or in series with at least one capacitor with a temperature-dependent capacitance value.
  • the capacitor circuit is designed in such a way that the temperature-dependent influence on the frequency of the crystal caused by it is intended to compensate for precisely that influence on the oscillator frequency which is caused by the temperature change of the crystal.
  • the frequency stability achieved with such circuits is not very satisfactory.
  • Significantly better results, namely stabilities of around 10 ppb are achieved if a crystal and its control circuit are housed in a very precisely controlled thermostat. Sometimes even a thermostat is used, which in turn is arranged in a thermostat.
  • a crystal oscillator compensation circuit has, in addition to a crystal which is excited to oscillate by a crystal oscillator scarf tuny, and an adjustable capacity for adjusting the oscillator frequency, a port, a memory, a temperature sensor and a logic circuit.
  • the port is used to connect a measuring device for measuring properties of the crystal. Key figures of the crystal calculated from the measurement data are stored in the memory mentioned.
  • the temperature sensor is arranged so that it always has the same temperature as the crystal, gives its temperature i gna 1 to the logic circuit, which emits a temperature compensation signal to the adjustable capacitance depending on the respective temperature signal, with a temperature change from a first temperature
  • the temperature compensation signal is changed by such an amount according to a known law, taking into account the stored key figures, that the resulting influence on shifting the oscillator frequency cancels the influence on the opposite shifting that is caused by the temperature change.
  • the circuit u. U. additionally, an acceleration sensor that outputs an acceleration signal to the logic circuit, which is used in accordance with the temperature signal to compensate for the frequency change effects caused by an acceleration change.
  • a third circuit according to the invention makes it possible to compensate for aging effects. This eliminates the need to use oscillator crystals that have been artificially aged at elevated temperature for a long time, and which are therefore relatively expensive. Rather, an inexpensive oscillator crystal that has just been manufactured can be used. Frequency effects due to aging change with a logarithmic function of time. The associated crystal constants for the function can be determined by measuring the oscillator frequency at different times. The logic circuit is then able, on the basis of the precisely defined function for the associated crystal and on the basis of a time measurement, to determine at any time that compensation voltage which compensates for the frequency change effect caused by aging.
  • the aging function is not simulated by the logic circuit but by a special aging circuit.
  • Such an aging circuit can be constructed so that it consumes very little power, e.g. B. only a few ⁇ A, while a logic circuit, e.g. B. a microprocessor has a power consumption of about 50 mA.
  • a battery of very low capacity preferably a Li battery, is sufficient to operate the aging circuit for a number of years, as a result of which the aging behavior, including temperature fluctuations, is reproduced exactly at any time, if the device in which the crystal is arranged, and thus also the logic circuit within the crystal oscillator compensation circuit, is not operated for a long time.
  • an oscillator circuit has circuitry within a crystal oscillator compensation according to the invention. device on an oscillator transistor, between the base and collector of the crystal, a decoupling capacitor and the capacitance diode are in the order mentioned.
  • the supply voltage is applied to the collector and the control voltage for the capacitance diode, which is obtained from the supply voltage taking into account the compensation signals, is supplied between the latter and the decoupling capacitor.
  • the capacitance diode is thus between two voltages that relate to a single voltage, which is also hardly temperature-dependent. Therefore, only the temperature response of the crystal has to be compensated, but not also a temperature response of the exciting circuit.
  • FIG. 1 shows a schematic illustration for explaining the cutting directions of oscillator crystals from a quartz single crystal 1;
  • Fig. 2 diagram for explaining the temperature-dependent frequency response of a quartz crystal
  • FIG. 4 is a block diagram of a crystal oscillator compensation circuit
  • Fig. 5 is a schematic block diagram for explaining the
  • FIG. 6 shows a circuit diagram for the control of a capacitance diode within an oscillator circuit which is part of the circuit according to FIG. 4; 7 shows a schematic block di agr amm for explaining the function of an acceleration sensor;
  • FIG. 8 shows a schematic perspective illustration for explaining the alignment of an acceleration sensor with respect to a quartz crystal
  • FIG. 10 is a circuit diagram of an aging circuit according to the block diagram of FIG. 9.
  • Fig. 10 for determining temperature dependence or the passage of time.
  • conventional quartz crystals 12 are approximately parallel to this direction AT from the Quartz single crystal 11 cut out in the form of cuboid bars.
  • the frequency at which such crystals are operated fluctuates within wide limits, of which oscillators in the range between 1-20 MHz are most frequently used, above all 5 MHz or 10 MHz. Other frequencies are usually obtained by dividing the frequencies mentioned.
  • the resonance frequency (or the anti-resonance frequency) of a quartz oscillator is temperature-dependent, which is shown in FIG. 2, time-dependent, which is shown in FIG. 3, and acceleration-dependent, which is not shown in more detail, since this effect is generally of minor importance.
  • the frequency response as a function of temperature suffices for certain laws. In the case of quartz in the AT cut direction, the law is a cubic parabola, for which the following applies:
  • f is the oscillation frequency
  • T is the temperature of the
  • Quartz and k a , k b and T o are constants that must be determined individually for each quartz and in particular depend on the deviation of the cutting direction from the AT direction.
  • FIG. 3 shows two aging profiles for a single quartz, namely the profile that the quartz has at a temperature T 1 and the profile that the quartz would have at a higher temperature T 2 (at a specific point in time) However, the quartz can only have a single temperature).
  • T 1 the profile that the quartz has at a temperature
  • T 2 the profile that the quartz would have at a higher temperature
  • the quartz can only have a single temperature.
  • the first section extends from the time of manufacture to two days after manufacture. During this time, crystals age very quickly. After that there is a considerably lower aging, which however takes place with increasing temperature according to the law exp (-k d / T). The time-related change is logarithmic. The following applies to the frequency response of aging:
  • k c and k d are constants that must be determined individually for each oscillator.
  • the capacitance diode 14 and the quartz 12 are connected in series via a decoupling capacitor 23.
  • the capacitance diode 14 is supplied with an analog compensation voltage U K by the D / A converter 21. This corresponds to a digital value which is supplied to the D / A converter 21 by the logic circuit 18 via a bus 24.
  • the logic circuit 18 calculates the digital value mentioned on the basis of the above-mentioned law for the temperature-dependent frequency response depending on the temperature reported by the temperature sensor 17.
  • This temperature sensor like the capacitance diode 14, is arranged in good thermal contact with the quartz 12, which is indicated by the dashed line, which includes the components mentioned.
  • the temperature sensor 17 outputs an analog signal to the analog / digital converter 22 which, after being converted into a digital signal, forwards it via the bus 24 to the logic circuit 18.
  • the bus is shown open at the bottom in FIG. 4 to indicate that other components may also be connected to it. Examples are listed below.
  • the described crystal oscillator compensation circuit 13 is arranged in a thermostat 25 which is heated by a heater 26 to a temperature which is regulated by a calibration circuit 27.
  • the calibration circuit 27 simultaneously monitors the signal from the temperature sensor 17, as it is fed through I / O port 15. If the temperature signal remains unchanged for some time, which indicates that constant temperature conditions have occurred, the calibration circuit 27 measures the frequency f as it is output by the crystal oscillator circuit 19. This frequency is the frequency of a frequency standard 28, z. B. an atomic clock.
  • the frequency standard is set to a frequency at which the oscillator circuit 19 is also intended to oscillate continuously. If a deviation of the frequencies is found, the calibration circuit changes the compensation voltage U ⁇ , which is guided by the capacitance diode 14, until the frequencies match.
  • the signal for setting the compensation voltage is fed to the crystal oscillator compensation circuit 13 via the I / O port 15.
  • the calibration circuit 27 storing the associated value for the signal for setting the compensation voltage for each temperature at which the adjustment process takes place. From e.g. B. five measuring points within a temperature range between -10 degrees Celsius and +60 degrees Celsius, the temperature-dependent characteristics of the present quartz, that is, the constants k a , k b and T o can be determined very precisely. These constants are given by the calibration circuit 27 via the I / O port 15 to the memory, which is no longer designed as a PROM 16 in the crystal oscillator compensation circuit 13 according to FIG. 5, but as an EEPROM 16.1. The use of an EEPROM has the advantage that the constants can be changed again later, e.g. B. if a recalibration takes place after a long time. This is also possible if a NOVRAM is used instead of the PROM 16.
  • the crystal oscillator compensation circuit 13 is separated from the calibration circuit 27 and is then available for use in a larger circuit which must be frequency-stabilized very precisely.
  • the crystal oscillator compensation circuit 13 functions in such a way that, in response to a respective signal from the temperature sensor 17, the logic circuit 18 calculates which compensation voltage U,.
  • the regularity stored there and a program stored there. must be supplied to the capacitance diode 14 to compensate for the frequency change effect caused by a change in temperature with respect to an earlier point in time.
  • the frequency f of the oscillator circuit 19 is kept constant with very high accuracy, namely an accuracy of about 10 ppb in a realized embodiment.
  • logic circuit 18 is formed by a CPU and RAM.
  • the CPU is operated at a frequency derived from the frequency f and the crystal oscillator circuit 19. This saves a separate clock oscillator for the logic circuit.
  • the control of the capacitance diode 14 is shown in more detail in the crystal oscillator circuit according to FIG. 6.
  • the oscillator circuit has an oscillator transistor 29, the emitter of which is grounded via a resistor.
  • the base receives voltage from the AGC 20 with the interposition of a capacitive voltage divider.
  • the capacitive voltage divider has, on the one hand, a capacitor 30 located between the base and earth and, on the other hand, a capacitor arrangement consisting of the quartz 12, the decoupling capacitor 23 and the capacitance diode 14.
  • the capacitance diode 14 is connected at its other connection to the collector of the oscillator transistor 29 and via an inductor 53 to a voltage source for supplying a supply voltage U v .
  • the control voltage is the above-mentioned compensation voltage U K. This is due to the legality described above with the help of be Written procedure obtained from the supply voltage U V.
  • the capacitance of the decoupling capacitor 23 (the decoupling relates to the direct voltage; the capacitor has a feedback effect for the occurring alternating voltage) is 30 pF, and that of the capacitance diode is adjustable between approximately 15 and 300 pF.
  • the decoupling capacitor 23 is of high quality.
  • the frequency signal f is tapped at the collector of the oscillator transistor 29 via an isolating amplifier 51, which ensures that load changes at the output have no effect on the oscillation behavior of the quartz oscillator circuit 19.
  • an oscillating capacitor 52 is also connected to ground at the collector, which, together with the inductor 53 also connected to the collector, forms an LC resonance circuit which is tuned to the desired frequency f.
  • This particularly advantageous circuit structure means that undesirable harmonics to frequency f and noise signals are filtered out, which are outside the bandwidth of the LC resonance circuit.
  • the isolation amplifier 51 receives only that with the desired frequency f as a strong signal.
  • the oscillator transistor 29 receives a signal from the automatic gain control circuit AGC 20. It is a conventional AGC for setting the power loss of the quartz oscillator 12.
  • the AGC 20 the quartz 12 operated at such a power that. there is no change in the oscillator properties compared to the non-vibrating state of the quartz.
  • a typical power value is around 0.5 mW. If the quartz 12 were operated at higher powers, the above-mentioned. Change constants in the law for the temperature-dependent frequency response. Other parameters of the crystal, e.g. B. in the law for the age-related frequency response would change.
  • a D / A converter 21 and a separate A / D converter 22 are not used, but the A / D converter is formed using the D / A converter, preferably using a weighing method ( one digit at a time) circuit. This also applies to the cases described below in which a measurement signal is fed to an A / D converter. This is cheaper and takes up less space than using a separate A / D converter.
  • the crystal oscillator compensation circuit 13 can be modified, further developed or configured in various directions.
  • a first further development is that, in addition to the temperature sensor 17, there is also an acceleration sensor 31, the housing 32 of which, as shown schematically in FIG. 8, is connected to the housing 33 of the quartz 12 via a base plate 34, for example a common one.
  • a printed circuit board is mechanically firmly connected, so that the acceleration sensor 31 experiences the same acceleration and direction as the quartz 12.
  • FIG. 8 shows that the acceleration sensor 31 has three sensor crystals 35.1 to 35.3 in three orthogonal spatial directions, which are denoted by a 1 , a 2 and a, respectively.
  • These sensor crystals 35.1 to 35.3 are aligned with their axes in relation to the cuboid quartz 12 in such a way that the directions mentioned run parallel to the cuboid edges.
  • These square edge directions represent the directions in which the oscillator frequency responds to changes in acceleration. It should be noted, however, that it depends on the cutting direction of the quartz 12 whether it is sensitive to acceleration in all three edge directions or not.
  • a quartz 12 which is cut exactly in the AT direction is essentially only sensitive to acceleration in the longitudinal direction. When using such a cut, the sensor crystals 35.1 and 35.2 could be saved, the directions of which lie parallel to the short edges of the quartz 12.
  • the acceleration sensor 31 sends an acceleration signal to the bus 24 via an analog / digital converter 36.
  • This acceleration signal is processed by the temperature sensor 17 in the same way as the temperature signal. That is, the crystal oscillator compensation circuit 13 is first calibrated for different accelerations, which is done by placing the crystal oscillator compensation circuit 13 on a vibrating table which is equipped with different ones Frequencies is operated. The calibration circuit 27 then takes measurements at different vibrations and in turn outputs a compensation voltage until, in spite of the acceleration effects, there is again no difference between the frequency of the oscillator circuit 19 and the frequency of the frequency standard 28. Characteristics determined during this calibration process are stored in EEPROM 16.1. If the crystal oscillator compensation circuit 13 is calibrated in this way with respect to changes in acceleration, a compensation of takes place during later operation
  • FIGS. 9 and 10 relate to an aging circuit 37.
  • This has a temperature-sensitive component 38, an oscillator circuit 39, a logarithmic counter 40, a battery 41, a micro fuse 42 and a short-circuit transistor 43.
  • Constants k c and k d are proportional to that equation as explained with reference to FIG. 3.
  • Counter 40 counts the clocks from the oscillator circuit 39 so that its count N does not increase proportionally with the number of clocks at its input, but only logarithmically with the
  • N k g e -k f / T lnt
  • the constant k g is proportional to the constant k c , which relates to the aging dependency of the frequency response in the equation explained with reference to FIG. 3.
  • the count value N is fed via the bus 24 to the logic circuit 18 (not shown in FIG. 9).
  • this calculates an aging compensation signal which is fed to the capacitance diode 14.
  • the logic circuit changes the aging compensation signal between a first point in time and a second point in time by such an amount that the resulting influence on shifting the frequency of the oscillator cancels the influence on the opposite shifting which is caused by the aging between the two points in time.
  • the key figures for calculating the aging compensation signal are again determined by a calibration process which corresponds to the calibration process for determining the key figures for the temperature dependence of the frequency response.
  • the frequency f output by the oscillator circuit 1-9 is changed by outputting a signal from the calibration circuit 27 to the I / O port 15 until it matches the frequency from the frequency standard 28.
  • the same process is repeated for several further points in time and the parameters are calculated from the compensation signals required in each case.
  • the oscillator circuit 39 has two oscillators, namely an oscillator 45, referred to as a T-oscillator, for determining the temperature dependence of aging and an oscillator 46, referred to as a t-oscillator, for measuring the time lapse since the aging circuit was started.
  • the T oscillator 45 is constructed as shown in Fig. 11a. It has a feedback operational amplifier 44a, at one input of which is the temperature-sensitive component 38 in the form of two diodes connected to one another.
  • the t-oscillator 46 is constructed accordingly, with a feedback operational amplifier ker 44b, at one input of which there is a resistor 54 instead of the diodes.
  • the logarithmic counter 40 has a first counter, which is referred to below as a time counter 47, a pre-settable counter 48 and a second counter, which is referred to below as the aging counter 49.
  • the time counter counts the pulses supplied to it by the t-oscillator 46.
  • the presettable counter 48 counts the pulses supplied to it by the T oscillator 45. It counts down from a preset value. As soon as it has reached the count value zero, it passes on a pulse to the aging counter 49. At the same time, it is set to a new value, namely the current count value of the time counter 47.
  • both the time counter 47 and the presettable counter 48 are set to a predetermined value at a starting point via a reset input, which indicates that the circuit starts up enables, for example to the value 2. It is further assumed that at the assumed constant temperature both oscillators 45 and 46 would oscillate at the same frequency. As a result, when the presettable counter 48 has counted down from the initial value 2 to 0, the time counter 47 has counted up from 2 to 4. The presettable counter 48 now gives a first pulse to the aging counter 49 and it is simultaneously set to the count value of the time counter 47, that is to say the value 4.
  • the temperature at the diodes 38 increases compared to the initially assumed value at which the two oscillators 45 and 46 oscillate at the same frequency.
  • the frequency of the T oscillator 45 then increases in accordance with the exponential law given above.
  • the presettable counter 48 then counts down faster than the time counter 47 counts up.
  • a pulse arrives at the aging counter 48 earlier than after a previous pulse than was the case at a lower temperature.
  • the count of the aging counter 49 thus increases in proportion to the product of the log of the time elapsed since the start of the circuit and the negative reciprocal of the temperature, corresponding to the
  • the T-oscillator 45 and the t-oscillator 46 are constructed essentially the same. As a result, the aging effects of these two oscillator circuits 45 and 46 in the logarithmic counter 40 cancel each other out. It also makes it possible to compensate for higher-order temperature effects on the two oscillators against one another if both of these are brought into good thermal contact with the monitored quartz crystal. Only the effects of the components which differ from one another are not compensated for, ie the strongly dependent temperature behavior of the diodes 38 is not compensated for by the weakly temperature-dependent behavior of the resistor 54. Exactly this is the purpose of the arrangement, namely only the temperature dependency of the diode properties unaffected by temperature dependent properties of the use other circuit components to simulate the temperature-dependent behavior of the monitored quartz crystal.
  • the equation describing the aging behavior of a quartz crystal includes a coefficient k g to be determined for each crystal specimen.
  • a corresponding coefficient is for the aging
  • the time counter will first overflow when the monitored quartz crystal is at a low operating temperature, and the aging counter if the temperature is continuously high. If one of these two counters overflows, the aging counter 49 would emit a signal which would be incorrect with regard to the desired simulation of the aging dependency of the quartz properties.
  • the overflow outputs of the two counters are connected to the base of a short-circuit transistor 43 which, when the overflow signal is applied to it, short-circuits a fuse 42 with respect to the battery 41, so that the fuse blows. This is determined via a signal line 50 and the signal emitted via this line ensures that the compensation circuit remains at the last determined value for the aging properties.
  • the fuse also disconnects the operating voltage U B from the active components of the aging circuit.
  • dividers were arranged in front of the time counter 47 and the aging counter 49 in order to make do with 12-bit counters despite the relatively high oscillation frequencies of the oscillators 45 and 46.
  • the frequency, the divider ratios and the counter capacities are matched to one another in such a way that the time counter 47 overflows after about 10 years.
  • the aging counter 49 overflows after about 7 years at a continuous operating temperature of 80 degrees Celsius, after about 7 years at a continuous operating temperature of 40 degrees Celsius.
  • the battery 41 uses a Li battery which, when the aging circuit 37 is operated continuously, has a significantly longer lifespan than 2 1/4 years, in order to ensure that the aging circuit is operated in the intended manner until the changed signal occurs on the signal line 50.
  • a very small battery with approximately 2 Ah already has a sufficient lifespan of, for example, five years, since the specified aging circuit 37 has a current consumption of only approximately 5 ⁇ A.
  • the overflow value of the LN counter 40 and the service life of the battery 41 are basically designed such that the residual aging after the fuse 42 has blown is negligible for the respective specification. In special cases, a new fuse can be used and the circuit 13 can be recalibrated.
  • the invention is applicable not only to any oscillator crystal, but also to any other component or circuit, provided that
  • Aging behavior is proportional to the logarithm of time and an exponential function, with the negative reciprocal of the temperature as an exponent. This applies in practice to all components with a crystalline structure and to circuits whose properties are largely determined by such components.
  • the frequency of a crystal oscillator can be controlled within certain limits by changing any reactive reactance. In practice, it has so far only made sense to control it with the aid of adjustable capacitances, in particular with capacitance diodes, which is why reference was only made to such control.
  • the capacitance diode is in series with the quartz. However, it is also possible to arrange the diode parallel to the quartz, but this can only be achieved in practice with little effort if a crystal oscillator is excited in its fundamental frequency. However, the series connection has proven to be more expedient in this case.
  • the memory for storing the crystal oscillator codes is an EEPROM or a NOVRAM, which, as described, has the advantage that new codes can be entered in a simple manner during a recalibration process. If it is not necessary to recalibrate, it is sufficient to use a one-time programmable ROM, e.g. B. an EPROM.
  • a one-time programmable ROM e.g. B. an EPROM.
  • other options e.g. B. optically programmable can be used, as they have recently been developed in research.
  • the logic circuit 18 is formed by a CPU and a RAM. However, it is also possible to carry out the calculations using a gate arrangement. There are two options.
  • the gate arrangement is constructed in such a way that it calculates compensation signals exactly according to the previously known law, taking into account the stored characteristic numbers and the measured temperature, a measured acceleration or a measured time course.
  • the other possibility is that detailed tables are created in the PROM 16 during calibration, in which a temperature compensation signal and a multiplicity of times a temperature compensation compensation signal are assigned to a multiplicity of temperatures, which also applies to accelerations or other influencing variables can take place.
  • the gate arrangement then only serves, depending on z. B. a measured temperature to address the PROM and to calculate the exact voltage value of the signal based on the table value for the compensation signal.
  • a structure requires a very complex calibration process.
  • An aging circuit 37 is not necessarily required to calculate an aging compensation signal. Rather, there is also the possibility of displaying the passage of time by means of a clock and continuously calculating the aging via the logic circuit 18 while taking into account the temperature signal from the temperature sensor 17. However, this requires an uninterrupted operation of the logic circuit 18 and thus a power consumption that is several orders of magnitude higher than that of the aging circuit 37.
  • a microprocessor has namely. B. a current consumption of about 50 mA, in contrast to the mentioned current consumption of the aging circuit 37 constructed according to FIG. 10 with an extremely low current consumption with a value of about 5 uA. It is therefore only sensible to carry out the aging compensation via the logic circuit 18 if the device in question is not dependent on battery operation or is operated without interruption.
  • any other storage device can be used instead of a micro fuse 42, which registers the occurrence of the overflow signal, e.g. B. when the overflow signal occurs, the entire crystal oscillator compensation circuit 13 can be switched on for a short time, namely until the fact of the overflow is stored in a memory location of the EEPROM 16.1,
  • second order effects can also be taken into account, e.g. B. the hysteresis effect, as explained with reference to FIG. 2.
  • Another possibility is to take into account a temperature dependence of the acceleration-related frequency response.
  • circuit according to the invention using SMD technology (surface mounted device), since a volume of only a few ccm can be achieved, that is to say orders of magnitude less than in conventional very well compensated crystal oscillators. If the circuit is cast with a good heat-conducting resin, it is ensured that all components have the temperature that is measured by the temperature sensor.
  • the preferred exemplary embodiment for the description was that of a compensation circuit for compensating for temperature effects. Circuits to compensate for acceleration or aging effects have only been shown as modifications or further developments. This ranking was done because temperature compensation is the most important compensation for practical applications. However, it is entirely possible to omit the temperature compensation if, for. B. a conventional A u fb a u is used in a thermostat. Then, however, the aging compensation is still useful if no pre-aged crystal is used, and / or acceleration compensation is useful if the circuit has strong accelerations, e.g. B. is exposed in missiles.

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Abstract

Un circuit compensateur à oscillateur à cristal (13) possède un cristal oscillateur (12) excité par un circuit à oscillateur piézoélectrique (19), la fréquence (f) pouvant être décalée dans certaines limites à l'aide d'une diode à capacité variable (14). La température du cristal est mesurée par un capteur de température (17) qui retransmet un signal de température par l'intermédiaire d'un convertisseur analogique/numérique (22) à un microprocesseur comportant un bus (24), un port d'entrée/sortie (15), une mémoire morte programmable PROM (16) et un circuit logique (18). Ce microprocesseur calcule, en fonction du signal de température compte tenu d'une régularité connue et de nombres caractéristiques, stockés dans la mémoire PROM, pour le cristal étudié, un signal de compensation de température, lequel est transmis par l'intermédiaire d'un convertisseur N/A (21) à la diode à capacité variable. Le signal de compensation de température (UK) présente une valeur telle que l'incidence qu'il produit sur la fréquence de l'oscillateur piézoélectrique compense exactement l'incidence sur la fréquence engendrée par la variation de température mesurée. Un tel circuit compensateur à oscillateur à cristal est bien moins onéreux et bien moins encombrant qu'un circuit correspondant classique de précision identique, qui exigeait des thermostats réglés avec une très grande précision. D'autres circuits compensateurs décrits servent à compenser les effets du vieillissement ou de l'accélération.
EP87905586A 1986-08-30 1987-08-28 Circuit compensateur a oscillateur a cristal Withdrawn EP0323466A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19863629588 DE3629588A1 (de) 1986-08-30 1986-08-30 Kristalloszillator-kompensationsschaltung
DE3629588 1986-08-30

Publications (1)

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EP0323466A1 true EP0323466A1 (fr) 1989-07-12

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EP87905586A Withdrawn EP0323466A1 (fr) 1986-08-30 1987-08-28 Circuit compensateur a oscillateur a cristal

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US (1) US4949055A (fr)
EP (1) EP0323466A1 (fr)
DE (1) DE3629588A1 (fr)
WO (1) WO1988001810A1 (fr)

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DE3823018A1 (de) * 1988-07-07 1990-01-11 Bosch Gmbh Robert Verfahren und vorrichtung zum entstoeren von mikroprozessor-schaltungen
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WO1988001810A1 (fr) 1988-03-10
US4949055A (en) 1990-08-14

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