JP2736431B2 - Crystal oscillator temperature compensation circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention generally relates to a temperature compensation circuit of a crystal oscillator. In particular, the present invention relates to one improved crystal oscillator temperature compensation circuit, which results in a very high degree of frequency stability, is fully integrated, and minimizes memory and process time. A combined digital / analog compensation circuit that provides independent compensation for each temperature segment.

2. Description of the Related Art An oscillator provided with a frequency determining crystal is often used to provide a stable output frequency. However, the crystals used in such oscillators are sensitive to temperature, and therefore, a temperature compensator is usually needed to maintain a stable oscillator output frequency. One generally accepted method is to generate a temperature variable voltage and apply it across a varactor to control the resonant frequency of the crystal oscillator.

In U.S. Pat. No. 4,254,382, Keller et al.
eller et al.) provide a compensation circuit that utilizes a three-stage circuit means to generate a non-linear temperature change for high and low temperature ranges and a linear temperature change for intermediate temperature ranges. Is disclosed.

In terms of a circuit, the outputs of the three circuits are combined, and a control voltage is generated together with the same temperature fluctuation as a crystal. While this measure works relatively well, this particular circuit requires more discrete components and seems to work best only with AT-cut crystals.
Moreover, the use of lasers in the manufacture of these crystals requires that all the crystals be grouped together, resulting in an overall lower yield.

With analog compensation methods, each has a separate compensation section that operates over a wide temperature range.
As the required frequency versus temperature stability increases over time, the degree of matching between the compensation circuit and the crystal has become critical. For this reason, close alignment must be maintained over a wide temperature range with limited adjustments to the compensation circuit. This is very difficult to do in a cost effective way. In particular, analog compensation sections usually have some interaction between them. With respect to digital compensation methods, this has the advantage that each compensation point is well defined for a particular temperature which facilitates easy processing. However, for a highly stable temperature compensated crystal oscillator having many temperature points and long processing times, there is a disadvantage that a very large memory and a large analog-to-digital converter are required. In addition, each oscillator will require a custom programmable memory device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved crystal oscillator which provides a high degree of frequency stability, is fully integrated and can provide high process (processing) yield for reliability. It is to provide a temperature compensation circuit.

It is another object of the present invention to provide AT-cut crystals having both positive and negative angles, as well as other types of crystals included within a specific temperature range, a specific maximum frequency deviation and a specific maximum slope. An object of the present invention is to provide a crystal oscillator temperature compensation circuit that can compensate.

[Means for Solving the Problems] According to one aspect of the present invention, means for varying the inclination,
A temperature compensation circuit is provided for an oscillator having a frequency determining crystal, including a variable slope generator with means for changing polarity and means for changing intercept.

According to another aspect of the invention, the apparatus includes a temperature detecting means, a means for accumulating data corresponding to a plurality of temperature ranges, and a frequency determining crystal comprising an analog-to-digital converter coupled to the temperature detecting means. A temperature compensation circuit for the oscillator is provided. The circuit further includes a variable slope generator having means for changing the slope, means for changing the polarity, and means for changing the intercept. The circuit also includes means for updating the temperature data of the compensation circuit.

In accordance with another aspect of the invention, a variable slope generator comprising means for detecting temperature, a generator, and means for varying the slope, means for changing polarity, and means for changing the intercept, coupled to the oscillator. A system is provided for compensating for the temperature of an oscillator having a frequency determining crystal including a temperature compensating circuit comprising a vessel. The circuit also includes means for storing data corresponding to the plurality of temperature ranges, the data storage means being coupled to the compensation circuit. The circuit further includes an analog-to-digital converter and includes means for updating the temperature information of the compensation circuit.

According to yet another aspect of the invention, a temperature variable comprising means for changing the slope, means for changing the polarity, means for changing the intercept, and means for setting the gain in the circuit over the entire operating range of the circuit. A circuit is provided for generating a variable temperature voltage including a voltage generator.

Accordingly, the configuration of the present invention is as described below. That is, a crystal oscillator having an output frequency determined by a crystal having a predetermined frequency versus temperature characteristic and a voltage dependent reactance (36) connected to the crystal and changing the output frequency of the crystal oscillator in response to an analog control voltage. A temperature compensating circuit (10) for storing data corresponding to a plurality of operating temperature ranges within an operating temperature range of the temperature compensating circuit (10), and a plurality of digital control signals based on the stored data. And a temperature dependent current generating means for generating a substantially linear current versus temperature change over a selected operating temperature range within an operating temperature range, the temperature dependent current generating means comprising: Is coupled to the memory means (12) and is responsive to a first digital control signal of the plurality of digital control signals to select a selected one of the operating temperature ranges within the operating temperature range. An adjustable current source (22) for generating a power supply current to a first analog voltage input terminal; a second analog voltage input terminal; and an analog current input terminal coupled to the current source (22) for receiving the power supply current. A single differential amplifier (20) having: a temperature sensor (14) connected to the first analog voltage input terminal of the differential amplifier (20) for generating a temperature-dependent output voltage proportional to an ambient temperature; And an operating temperature range coupled to the second analog voltage input terminal of the memory means (12) and the differential amplifier (20) and responsive to a second digital control signal of the plurality of digital control signals. A voltage generator (18) for generating a constant analog reference voltage over the selected operating temperature section within the differential amplifier (20), wherein the differential amplifier (20) Generating a substantially linear current-to-temperature change in response to a difference voltage between the input voltage and the analog reference voltage of the voltage generator; A circuit (10) is coupled to an output terminal of the memory means (12) and the differential amplifier (20) and is substantially linear in response to a third of the plurality of digital control signals. Polarity change means (2) to change the polarity of
6), the memory means (12) and the tilt polarity changing means (2
And a substantially linear current-to-temperature change-adjusted magnitude responsive to a fourth digital control signal of the plurality of digital control signals. A current level adjusting means (28) for generating a linear current versus temperature change; a fifth digital signal of the plurality of digital control signals coupled to the memory means (12) and the current level adjusting means (28); Applying a DC current to the adjusted substantially linear current versus temperature change in response to a control signal;
DC offset means (30) for generating a temperature-dependent current adjusted to DC, an output terminal of the current level adjusting means (28) and the DC
Means (32) coupled to the output terminal of the offset means (30) for generating an analog control voltage in response to the DC regulated temperature dependent current; and output of the means (32) for generating the analog control voltage To limit peak phase shift during transitions between a plurality of operating temperature segments, and to couple the analog control voltage to the voltage dependent reactance (36) to provide a temperature of the crystal oscillator over an operating temperature range. A temperature compensating circuit (10) for a crystal oscillator characterized by comprising a filter means (34) for compensating.

Alternatively, a second temperature sensor (15) for generating an analog output voltage proportional to an ambient temperature, the memory means (12) and the second temperature sensor (15)
Is connected to one output terminal of the second temperature sensor (1
Generating a digital output signal in response to the analog output voltage of 5) and providing the digital output signal to the memory means (12), wherein the memory means (12) uses the digital output signal An analog-to-digital converter (16) for selecting specific stored data and generating a plurality of digital control signals, wherein the temperature-compensating circuit (10) for the crystal oscillator is provided. .

Alternatively, the memory means (12) has a structure as a temperature compensation circuit (10) of a crystal oscillator, which is provided with a programmable data storage device.

Alternatively, the programmable data storage device comprises:
It has a configuration as a temperature compensation circuit (10) of a crystal oscillator characterized by comprising an electrically erasable programmable read only memory (EEPROM).

Alternatively, the DC offset means (30) has a configuration as a temperature compensation circuit (10) for a crystal oscillator, comprising a plurality of adjustable current mirrors and a plurality of load resistors.

Alternatively, the temperature sensor (14) has a configuration as a temperature compensation circuit (10) of the crystal oscillator, which includes a diode connected in series.

Alternatively, the current source (22) has a configuration as a temperature compensation circuit (10) for a crystal oscillator, comprising a plurality of adjustable current mirrors.

Alternatively, the memory means (12), the temperature-dependent current generating means (14, 18, 20, 22) and the gradient polarity changing means (2
6), the current level adjusting means (28), the DC offset means (30), the means for generating the analog control voltage (32), and the filter means (34) are all integrated to form one integrated circuit. It has a configuration as a temperature compensation circuit (10) of a crystal oscillator characterized by being configured.

Alternatively, a crystal oscillator having an output frequency determined by a crystal having a predetermined frequency versus temperature characteristic and a varactor connected to said crystal and changing an output frequency of the crystal oscillator in response to an analog control voltage. A temperature compensation circuit (10), which stores data corresponding to a plurality of operating temperature sections within an operating temperature range of the temperature compensation circuit (10), and outputs a plurality of digital control signals based on the stored data. Generated electrically erasable programmable read only memory (EEPROM) (12) and temperature-dependent current generation temperature that produces a substantially linear current-to-temperature change over a selected operating temperature range within the operating temperature range The temperature-dependent current generating means is coupled to the electrically erasable programmable read only memory (EEPROM) (12), An adjustable current source (22) for generating a power supply current for a selected operating temperature segment within an operating temperature range in response to a first digital control signal of the digital control signals; a first analog voltage input terminal; A single differential amplifier (20) having a second analog voltage input terminal and an analog current input terminal coupled to the current source (22) for receiving the power supply current; A diode temperature sensor connected to one analog voltage input terminal to generate a temperature-dependent output voltage proportional to an ambient temperature; an electrically erasable programmable read only memory (EEPROM); An amplifier coupled to the second analog voltage input terminal and responsive to the second digital control signal of the plurality of digital control signals, the selected one of the plurality of digital control signals within the operating temperature range. Constructed from over the operating temperature divided voltage generator for generating a constant analog reference voltage (18), wherein said differential amplifier (20)
Generates a substantially linear current versus temperature change in response to a difference voltage between the temperature dependent output voltage of the diode temperature sensor (14) and the analog reference voltage of the voltage generator (18). The temperature compensation circuit (10) of the crystal oscillator is further coupled to output terminals of the electrically erasable programmable read only memory (EEPROM) (12) and the differential amplifier (20). Gradient polarity changing means for changing the polarity of a substantially linear current versus temperature change in response to a third digital control signal of said plurality of digital control signals.
Said electrically erasable programmable read only memory (EEPROM) (12) and said gradient polarity changing means (2).
And a substantially linear current-to-temperature change-adjusted magnitude responsive to a fourth digital control signal of the plurality of digital control signals. A current level adjusting means (28) for generating a linear current versus temperature change; and an electrically erasable programmable read only memory (EEPROM) (12) and the current level adjusting means (28); Applying a DC current to the adjusted substantially linear current versus temperature change in response to a fifth digital control signal of the plurality of digital control signals;
A plurality of adjustable current mirrors for generating a temperature-dependent current adjusted to DC, coupled to an output terminal of the current level adjustment means (28) and an output terminal of the plurality of adjustable current mirrors;
A load resistor (32) for generating an analog control voltage in response to the DC-dependent temperature dependent current; and a load resistor (32) for generating the analog control voltage, A filter (34) for controlling the peak phase displacement during the transition period between and coupling the analog control voltage to the varactor (36) for temperature compensation of the crystal oscillator over an operating temperature range. Temperature compensation circuit for crystal oscillator (1
0).

SUMMARY OF THE INVENTION The present invention relates to a fully integrated temperature compensation (TC) circuit for a crystal oscillator. This circuit has a very high degree of frequency stability,
In addition, it is possible to compensate for various cuts and angles of the crystal. In particular, the compensation circuit is one analog TC circuit, having digitally selected parameters, using programmable slope, intercept and polarity, and generating a new TC voltage curve every 4 ° C . The current and current mirror of one differential pair control the slope of the TC voltage. One differential operating voltage is switched to control the polarity of the voltage ramp, while one differential pair bias and one operating current source set the voltage intercept.
The temperature variable diode voltage drives the differential pair, while the key memory updates the memory contents of one EEPROM.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, together with many other advantages and its possibilities, reference is made to the following description and appended claims, taken in conjunction with the accompanying drawings.

According to the teachings of the present invention, the temperature compensation circuit is a hybrid circuit between analog compensation and digital compensation. Pure analog compensation is 1 ppm (part per millimeter
on) (10 ^-6 ) stability requires extensive extensive processing. Pure digital compensation requires a large memory and a single ALU with many processing temperatures or curve-fitting capabilities. This only allows temperature compensation of the better-fitting curve-fitting quartz. This hybrid compensation circuit allows analog compensation over a 4 ° C. interval for less processing temperature and smaller memory capacity. The analog compensation of this particular circuit is changed every 4 ° C. so that all prior art circuits are affected by previous temperature compensation, but all temperature segments are independent of the others. It is possible. This greatly simplifies the process because the hybrid compensation has five independent circuit controls, each for every 4 ° C. interval, while most temperature-compensated crystal oscillators It has only four interacting adjustments over the entire range of 130 ° C.

According to the teachings of the present invention, the temperature compensation circuit was designed to operate with either a hyper abrupt junction varactor as a discrete component or with an integrated step junction varactor. Operation over a small temperature range allows for the use of non-linear varactors and, as a result, makes it possible to introduce an overall integration of the temperature compensation circuit. Also, the small temperature range allows the use of EEPROM MOS technology,
Therefore, it has a large temperature coefficient of resistance. Furthermore, this compensation circuit can be used for AT, BT and GT within the aforementioned limits.
Can be used with various crystal face cuts. The compensation circuit can also be reprogrammed without affecting the reliability of the package or interconnect.

Referring now to FIG. 1, there is illustrated a block diagram of a temperature compensation circuit 10 used in an oscillator having a frequency determining crystal. Although the figures illustrate some portions of the temperature compensation circuit, most of the operation of the circuit occurs substantially, but not exclusively, within a single stage. The stage essentially comprises a variable current or ramp voltage generator comprising means for changing the slope, means for changing the polarity, and means for changing the intercept. The generator also includes means for setting the gain of the circuit. The components of the generator are shown in FIG. 1 and described in more detail below.

FIG. 1 is a block diagram illustrating the operation of the compensation circuit 10 for a particular temperature range. The compensation circuit of the present invention comprises a programmable data storage device, such as an EEPROM, for storing data corresponding to a plurality of temperature ranges to readjust the analog portion of the compensation circuit. In one embodiment, one EEPROM with 32 rows of memory having 22 bits per row is used to store temperature data. Each row of the EEPROM corresponds to a temperature range of 4 ° C. In FIG. 1, one row of the memory 12, together with its corresponding bit, is shown for a particular temperature range. Each row of memory has a fine slope, temperature bias point, polarity, coarse slope (coarsesl).
ope) and a bit of information for a fixed offset can be stored. Thus, the inherent temperature compensation voltage for a temperature range of every 4 ° C., programmable slope, intercept (offset), and polarity, all of which originate primarily from a single stage slope generator, It is generated by using.

The temperature compensation circuit 10 includes a temperature sensor 14 and an analog / digital (A / D) converter 16. In one embodiment, the temperature sensor 14 comprises three series diodes that represent one analog diode voltage.
Temperature sensor 14 digitally adjusts the current to set the nominal voltage and temperature ramp of the circuit. A /
The D converter 16 digitizes an analog voltage from the temperature sensor 15 similar to the temperature sensor 14, and then selects a row of the memory according to the temperature and addresses data (address specification) from the EEPROM. The temperature compensation circuit 10 also includes a bias decoder 18, a differential amplifier 20, a programmable current source 22, and a current load 24.

FIG. 2 illustrates a differential stage for a temperature compensation circuit. Referring to FIG. 2, in generating a variable current, a temperature sensor 14 for displaying a variable voltage and a bias decoder 18 for displaying a fixed voltage are combined in a differential amplifier 20 to operate as a differential input pair. I have. A programmable current source 22 is also provided to the differential amplifier 20 using the temperature sensor 14 as a temperature dependent input voltage to generate a programmable temperature variable current. Second
As can be seen in the figure, a programmable current source
22 may consist of a set of current mirrors,
On the other hand, the bias decoder 18 that limits the operation range of the differential pair
May be a programmable voltage divider. Differential amplifier
The output 20 is a variable temperature current, but is supplied to a current load 24.

Referring again to FIG. 1, the temperature compensating circuit 10 further includes a polarity changing means 26 ("LO") of the output of the temperature variable current generator.
The polarity changing means 26 includes, as its inputs, the voltage from the current load 24 and the “POLARITY” of the memory 12.
From the row (1) or (0). The polarity changing means 26 configured in a circuit essentially changes the polarity of the differential output of the differential amplifier 20. The temperature compensation circuit 10 also has a variable current mirror 28. Here the variable current mirror 28
Contains a circuit for setting the gain of the circuit, the memory 12
In addition to the one input "coarse slope" from the second row, the input from "LOGIC" of the polarity changing means 26 can be received.

The temperature compensation circuit 10 further includes a current source array 30 and a load resistor 32 for correcting a fixed offset of the current gradient. The load resistance 32 also has a value of 1
Variable current mirror 28 to generate one output voltage
Holds input from Both the temperature compensation circuit 10 includes a filter 34 that limits the peak phase shift during periods of temperature range variation and separates the compensation circuit. Filter 34
Can attenuate radio frequency (RF) signals from the oscillator and reduce variations in the compensation circuit.
And finally, the temperature compensating circuit 10 outputs
Varactor diode 36 controlled by temperature variable voltage
To compensate for the frequency versus temperature response of the oscillator. The varactor diode 36 changes a variable voltage into a variable reactance in the circuit.

Referring now to FIG. 2, a temperature sensor 14, a bias decoder 18, a programmable current source 22, and a differential amplifier
A temperature compensated differential stage including 20 is shown. Programmable current source 22 serves to set the slope of the compensation voltage. The numbers given as different components of this circuit are given only as examples,
It does not limit the possibilities of circuit design. For example, the numbers in the bias decoder 18 relate to the temperature sensor 14, which here maintains a diode voltage of about 1.95V at 25 ° C and a temperature gradient of -6mV / ° C.

FIG. 3 illustrates a series of TC voltage versus differential bias curves generated for different values of a programmable current source 22 that sets the slope of the compensation voltage.
The desired slope gradient for a particular temperature range of quartz is expressed by a straight line tangent to the required oscillator compensation curve shown in FIG. 4, with the tangent points located between -20 ° C and -24 ° C. ing. FIG. 4 also illustrates a biased temperature point.

Bias decoder 18 sets a biased temperature point for the differential pair in differential amplifier 20. In this embodiment, the bias decoder 18 includes a tapped resistor that allows the use of a single differential pair over the entire temperature range by varying the bias temperature point for each temperature range. Has become. The tap resistor effectively adjusts the temperature projected compensation voltage to approximate a straight line tangent to the required compensation curve illustrated in FIG. Any programmable voltage or current source may be replaced by a tap resistor depending on the application of the circuit. The output of the differential amplifier 20 is directed to a current load 24 having outputs represented by OUT1 and OUT2. The output of the current load 24 is then
It is led to the circuit of the polarity changing means 26 shown in FIG.

FIG. 5 shows a temperature compensating gradient polarity circuit composed of the polarity changing means 26. The polarity of the compensation voltage gradient must be changed to match the gradient of the uncompensated characteristic of the crystal. Typically, individual differential stages will be used to change the polarity of each gradient. This circuit uses a single differential pair with a programmable slope as described in FIG. 2 to affect the slope polarity change. Output of differential stage
By inputting OUT1 and OUT2 to either an N-channel current mirror or a P-channel current mirror, the polarity is inverted. If a positive slope is required, a high ("1") level signal is input at input 38, the pressure at OUT1 is input to the P-channel current mirror, and the output at OUT2 is the N-channel current. The circuit is activated by being input to the mirror. For a negative slope, a low (“0”) level signal is applied to input 3.
In FIG. 8, the output of OUT2 is input to the P-channel current mirror, and the output of OUT1 is input to the N-channel current mirror, thereby activating the circuit. Temperature resolution (temper) for slope reversal
ature resolution) is about 2 ° C. This figure is sufficient because quartz suitable for temperature compensation typically has a very low frequency (or voltage) gradient to temperature near the turning point of the gradient.

Referring now to FIG. 6, a circuit diagram for the variable current mirror 28 of FIG. 1 is shown. The circuit of FIG. 6 shows a variable current mirror 28 for the differential stage.
The programmable current mirror stage has two inputs IN1 and IN2 (corresponding to OUT1 and OUT2), a P-channel current mirror 40, an N-channel current mirror 42, and a SENS sensitivity terminal
44 and gain terminals 46 and 48. Input (I
N) The control voltage at 1 generates a current flowing through the P-channel current mirror 40 by first setting a mirror current to the load resistance at a ratio of 4: 3. For each temperature range, this ratio is reprogrammed to reflect like a mirror in a ratio of 4: 3, 4: 6, 4: 9 and 4:12 according to the required gradient of the required intensity. Will be done. The control voltage at input (IN) 2 input to N-channel current mirror 42 operates in a similar manner as at input (IN) 1. SENS sensitivity terminal 44 shown
Does not change with temperature, but is used to adjust the compensation circuit for variations in the parameters of the IC manufacturing process. Gain terminals 46 and 48 are inputs derived from information stored in the memory. Such information is stored in a particular row of memory for a particular temperature range, as illustrated in FIG. 1 as "coarseslope".

Referring now to FIG. 7, a curve illustrating the effect of programming the variable current mirror circuit of FIG. 6, when compared to the curve in FIG. 3, namely, the temperature compensation (TC) voltage and the differential bias. (Having a multiplication value that is three times the multiplication shown in FIG. 3). For a differential curve of 4 × (10 μA) and a differential bias of 100 (mV), the compensation voltage change of +/− 40 mV is:
It is observed at a constant (fixed) multiplier ratio of 1 (FIG. 3). On the other hand, +/− 125 mV is observed for a current multiplier ratio of 3 (FIG. 7).

Referring now to FIG. 8, in the circuit diagram, a filter 34 and a current source array 30 and a load resistor 32 both for limiting peak phase shift and isolating the compensation circuit during temperature range variations. Are shown for the fixed offset correction. The mechanism for fixed offset correction is used in a manner similar to programmable bias for differential pairs.

Referring to FIG. 9, for a given temperature range, FIG. 9 shows the temperature compensation (TC) voltage curve of FIG. 4, two TC voltage lines lower than the required TC curve (best differential bias), and FIG. 5 illustrates a TC voltage 1 (desired bias) line indicating the required offset correction. Thus, TC voltage 1 is substantially tangent over a particular temperature range so that it approximates the best needed TC voltage. The differential bias defines the operation of the differential pair such that the slope generated cancels the oscillator frequency versus temperature gradient. Since the TC voltage 1 line is substantially in contact with the required temperature compensation voltage curve, the oscillator will also be on one frequency. The frequency error of the oscillator is determined by how much the compensation voltage is offset from the required curve, which has been shifted to another form by the sensitivity of the oscillator. This is illustrated in FIG. 9 and is labeled as offset correction.

The mechanism of fixed offset correction in the compensation circuit improves the resolution of the differential bias circuit by adding a small current with the compensation current to reduce the resulting frequency step. The results of this current are shown in FIG. 10 and FIG. FIG. 10 illustrates the differential bias correction plotted on a graph representing the relationship between the offset correction voltage and the current increase. Where the current increase is 1 to 2.5μA per step
/ Step. FIG. 11A illustrates a frequency vs. temperature curve, where there is no offset correction and the resulting offset from the step size of the differential bias resistor. The curve of TC voltage 1 is parallel to the tangent, but does not touch the required compensation voltage curve of the uncompensated oscillator as shown in FIG. FIG. 11B shows the compensated result after programming several offset correction increments.

Returning briefly to FIG. 8 here, the filter 34
Can be used as an RF filter to attenuate the RF signal from the oscillator connection to keep the compensation circuit independent of electromagnetic interference, and to reduce the transient response signal generated in the compensation circuit during switching and to reduce the TC voltage terminal Also operates as a filter for limiting the maximum displacement applied to the varactor diode. The fast settling time of the circuit ensures that the overall phase shift due to switching is minimal.

FIG. 12 illustrates a sample temperature compensation curve (frequency vs. temperature) for the described compensation circuit. As can be seen, the curve is represented using a 4 ° C. temperature step, limited to a frequency of about +/− 0.2 ppm for the entire temperature range.

FIG. 13 illustrates a block diagram of a temperature compensation system 50 that includes a temperature compensation circuit integrated with the crystal oscillator 52 and includes a mechanism for updating compensation circuit temperature information.
Reference numeral 15 denotes a second temperature sensor. The frequency of the oscillator is divided down in the shift register by a sequencer / anti-dither circuit 54, providing a slow clock to update the compensation every 15 to 30 seconds. Sequential circuit /
The anti-dither circuit 54 prevents variations between adjacent A / D segments by requiring several consecutive display records to match before updating the compensation information. Sequencing / anti-dither circuit 54 drives A / D converter 16 to provide a digital unit of temperature represented by temperature sensor 15. One address decoder 56 is a memory, in this case an EEPROM
From OM58, this information is used to select the correct parameters to compensate at this temperature. The temperature compensation (TC) data is latched by the TC latch 60 as shown, and the circuit operates like a single analog temperature compensation circuit until the next digital temperature update. Sequencing / anti-dither circuit 54 helps to start and update the compensation system periodically. A programmable divider 62 or similar device is used to adjust the output frequency of the system to meet customer specifications without having to change to another crystal or change the package of the oscillator. The frequency adjusting device 64 is used to adjust the circuit with respect to the aging of the crystal.

The temperature compensation circuit described here is not limited to temperature compensation of a crystal oscillator. This temperature compensation circuit may be used as a temperature compensation circuit for generating a variable temperature voltage. Such a temperature compensation circuit includes a single-stage variable voltage generator with a temperature sensor, a programmable current source, a programmable voltage divider for selecting a temperature range, a differential pair, and a variable current mirror coupled to a polarity change circuit. Will be provided. The differential pair is a current source,
It will have a voltage divider and a temperature sensor as input. This temperature compensation circuit would be used to generate a different voltage vs. temperature characteristic than the normal frequency vs. temperature characteristic, as in an automatic gain control circuit.
This temperature compensation circuit is very versatile. because,
This is because it can be programmed for a sawtooth or parabolic curve other than a smooth curve for quartz. Eventually, this temperature compensation circuit can also be operated digitally, even on a temperature compensation circuit that has already been roughly compensated.

Thus, using this temperature compensation circuit, new combination values are inserted to re-correct the temperature compensation every 4 ° C. and generate a new voltage curve. The differential pair current and the current mirror control the temperature compensation voltage gradient.
The differential output is switched to control the voltage gradient polarity, while the differential pair bias and offset current sources set the voltage intercept. The diodes drive the differential pairs and similarly adjust and update the contents of the EEPROM memory.

Accordingly, an improved temperature compensation circuit and system has been shown and described that satisfies the need for reduced size and cost due to its MOS type. The temperature compensating circuit is all integrated for small size and high reliability, and the number of components required in the compensating circuit is minimized. AT cut at both positive and negative angles, just like any other cut surface crystal, with a maximum frequency deviation of +/- 20 ppm and a maximum gradient of 2 ppm / ° C in the temperature range from -35 ° C to 95 ° C Other advantages include the ability to compensate for the crystal.

EEPROM memory also offers the advantage of reprogramming a single temperature range to limit scrapping due to crystal imperfections. The simplicity and compactness of this particular design is new to temperature compensation circuits and systems.

While the preferred embodiment of the invention has been illustrated and described herein, it is to be understood that various changes and modifications could be made without departing from the spirit and scope of the invention as defined by the appended claims. It will be apparent to those skilled in the art that this may not be the case.

[Brief description of the drawings]

FIG. 1 is a block diagram of a temperature compensation circuit representing a temperature compensation operation for a single row memory. FIG. 2 illustrates a differential stage for a temperature compensation circuit. FIG. 3 illustrates the curve formed by the programmable current source that sets the slope of the temperature compensation voltage. FIG. 4 illustrates a graph of the required temperature compensation voltage curve and a straight line having a desired slope tangent to the curve. FIG. 5 illustrates a circuit diagram of a gradient polarity circuit using a single differential pair with a programmable gradient. FIG. 6 illustrates a programmable current mirror circuit. FIG. 7 illustrates a curve representing the effect of programming the current mirror of the circuit. FIG. 8 shows a circuit for the precision offset mechanism and the compensation filter. FIG. 9 illustrates an exploded view of one of the illustrated compensation voltage versus temperature curves for a fixed offset mechanism. FIG. 10 shows a graph of differential bias correction. 11A and 11B illustrate the step size of the differential bias resistor and the offset resulting from the correction accordingly. FIG. 12 illustrates a graph of sample temperature compensation for a crystal oscillator in accordance with the teachings of the present invention. FIG. 13 shows a block diagram of a temperature compensation system including a temperature compensation circuit integrated in the oscillator. 10: Temperature compensation circuit for crystal oscillator 12: Memory (one row) (22 bits) 14: (First) temperature sensor 15: (Second) temperature sensor 16: A / D conversion Unit 18 bias decoder (reference voltage) (programmable voltage source) 20 differential amplifier 22 current source (programmable current source) 24 current load 26 programmable gradient polarity changing means 28 variable current mirror 30 Current source array 32 Load resistance 34 Filter (means) 36 Varactor diode (reactance depending on voltage) 38 Input 40 P-channel current mirror 42 N-channel current mirror 44 … SENS sensitivity terminals 46,48… Gain terminals 50… Temperature compensation system 52… Oscillator 54… Sequential circuit / anti-dither circuit 56… Address decoder 58… EEPROM 60… TC (temperature compensation) latch 62… … Programmable Division circuit 64 …… Frequency adjustment device

Continuing on the front page (72) Inventor Gretz Richard Ritzhitshuidor 55 117, Minnesota, United States, E Country Road B, No. 2,165, Apartment No. 227, Apartment 227 (72) Inventor Anthony Francis Keller 60655, Illinois, USA, St. Louis, Chicago, 10443 (72) Inventor Lawrence Edwin Cornell 60565, Illinois, USA, Napaville, Rio Grand Circle, 2464 (72) Inventor Michael William Schieringer, Alarington Heights, Illinois, USA 6004, N. Harvard, No. 1016 (56) Reference JP-A-62-235807 (JP, A) JP-A-62-200804 (JP, A) JP-A Sho 60 -154716 (JP, A) "PROCEEDINGS OF THE 23rd ANNUAL SYM OSIUM ON FREQUENCY CONTROL 6-7-8 MAY 1969 "(1969-5) ELECTRONI C INDVSTRIES ASSOCI ATION (US) P. 187-191

Claims (9)

(57) [Claims] A quartz crystal having a predetermined frequency versus temperature characteristic;
A voltage-dependent reactance (3) connected to the crystal and changing the output frequency of the crystal oscillator in response to an analog control voltage.
6) a temperature compensating circuit (10) of the crystal oscillator having an output frequency determined by: (c) storing data corresponding to a plurality of operating temperature sections within an operating temperature range of the temperature compensating circuit (10); And memory means (12) for generating a plurality of digital control signals based on the stored data; and temperature dependent for producing a substantially linear current versus temperature change over a selected operating temperature section within the operating temperature range. Current generating means, the temperature dependent current generating means being coupled to the memory means (12) and responsive to a first digital control signal of a plurality of digital control signals for selecting a selected one within an operating temperature range. An adjustable current source for generating a power supply current for an operating temperature section; a first analog voltage input terminal; a second analog voltage input terminal; and the power supply coupled to the current source. A single differential amplifier having an analog current input terminal for receiving a current; and a temperature-dependent output voltage connected to the first analog voltage input terminal of the differential amplifier, the output voltage being proportional to ambient temperature. A temperature sensor (14) to be generated; a second analog voltage input terminal of the memory means (12) and the differential amplifier (20); and a second digital control signal of the plurality of digital control signals. A voltage generator (18) responsive to generating a constant analog reference voltage over the selected operating temperature segment within the operating temperature range, wherein the differential amplifier (20) includes the temperature sensor (18). Generating a substantially linear current versus temperature change in response to a difference voltage between the temperature dependent output voltage of 14) and the analog reference voltage of the voltage generator (18). The water An oscillator temperature compensation circuit (10) is coupled to the memory means (12) and the output terminal of the differential amplifier (20), and is substantially responsive to a third digital control signal of the plurality of digital control signals. Polarity changing means (26) for changing the polarity of a linear current versus temperature change
And the memory means (12) and the inclination polarity changing means (26).
And a substantially linear current-to-temperature-adjusted magnitude adjusted in response to a fourth digital control signal of the plurality of digital control signals. Current level adjusting means (28) for generating a large current-temperature change, the memory means (12) and the current level adjusting means (2
8) coupled to the fifth digital control signal of the plurality of digital control signals, wherein the direct current is applied to the adjusted substantially linear current versus temperature change to be adjusted to direct current. DC offset means (30) for generating a temperature-dependent current, and a temperature-dependent current adjusted to the direct current coupled to an output terminal of the current level adjustment means (28) and an output terminal of the DC offset means (30). Means (32) for generating an analog control voltage in response to the signal; coupled to an output of the means (32) for generating the analog control voltage to limit peak phase displacement during a transition between a plurality of operating temperature segments. And a filter means (34) for coupling the analog control voltage to the voltage-dependent reactance (36) to compensate the temperature of the crystal oscillator over an operating temperature range. Vessels of the temperature compensation circuit (10). A second temperature sensor (15) for generating an analog output voltage proportional to the ambient temperature; and a memory (12) coupled to one output terminal of the second temperature sensor (15); Second temperature sensor (15)
And generating a digital output signal in response to the analog output voltage of the digital output signal, and providing the digital output signal to the memory means (12). An analog for selecting stored data and generating a plurality of digital control signals;
The temperature compensation circuit (10) for a crystal oscillator according to claim 1, further comprising a digital converter (16). 3. A temperature compensation circuit (10) for a crystal oscillator according to claim 1, wherein said memory means (12) comprises a programmable data storage device. 4. The temperature compensation circuit according to claim 3, wherein said programmable data storage device comprises an electrically erasable programmable read only memory (EEPROM). 5. The temperature compensation circuit of claim 1, wherein said DC offset means comprises a plurality of adjustable current mirrors and a plurality of load resistors. 6. The temperature compensation circuit (10) for a crystal oscillator according to claim 1, wherein said temperature sensor (14) comprises a diode connected in series. 7. A temperature compensation circuit (10) for a crystal oscillator according to claim 1, wherein said current source (22) comprises a plurality of adjustable current mirrors. 8. The memory means (12), the temperature-dependent current generating means (14, 18, 20, 22) and the inclination polarity changing means (2).
6), the current level adjusting means (28), the DC offset means (30), the means for generating the analog control voltage (32), and the filter means (34) are all integrated to form one integrated circuit. The temperature compensation circuit (10) for a crystal oscillator according to claim 1, wherein the temperature compensation circuit (10) is configured. 9. A quartz crystal having a predetermined frequency versus temperature characteristic,
A temperature compensation circuit (10) for the crystal oscillator having an output frequency determined by a varactor (36) connected to the crystal and changing an output frequency of the crystal oscillator in response to an analog control voltage, wherein the temperature compensation circuit An electrically erasable programmable read-only memory (EEPROM) that stores data corresponding to a plurality of operating temperature ranges within the operating temperature range of (10) and generates a plurality of digital control signals based on the stored data. (12); and temperature dependent current generating means for generating a substantially linear current versus temperature change over a selected operating temperature section within an operating temperature range, wherein said temperature dependent current generating means comprises: Responsive to a first digital control signal of a plurality of digital control signals, coupled to an electrically erasable programmable read only memory (EEPROM) (12) An adjustable current source for generating a power supply current for a selected operating temperature range within an operating temperature range, a first analog voltage input terminal, a second analog voltage input terminal, and the current source. A single differential amplifier (20) coupled to the first analog voltage input terminal of the differential amplifier (20) and having an analog current input terminal for receiving the power supply current; A diode temperature sensor for generating a temperature-dependent output voltage, coupled to the electrically erasable programmable read only memory (EEPROM) and the second analog voltage input terminal of the differential amplifier; Generating a constant analog reference voltage over the selected operating temperature segment within the operating temperature range in response to a second digital control signal of the plurality of digital control signals. Is composed from a voltage generator (18) which, wherein said differential amplifier (20)
Generates a substantially linear current versus temperature change in response to a difference voltage between the temperature dependent output voltage of the diode temperature sensor (14) and the analog reference voltage of the voltage generator (18). The temperature compensation circuit (10) of the crystal oscillator is further coupled to output terminals of the electrically erasable programmable read only memory (EEPROM) (12) and the differential amplifier (20). Gradient polarity changing means for changing the polarity of a substantially linear current versus temperature change in response to a third digital control signal of said plurality of digital control signals.
Said electrically erasable programmable read only memory (EEPROM) (12) and said gradient polarity changing means (26)
And a substantially linear current-to-temperature-adjusted magnitude adjusted in response to a fourth digital control signal of the plurality of digital control signals. Current level adjusting means (28) for generating a large current-temperature change; the electrically erasable programmable read only memory (EEPROM) (12); and the current level adjusting means (2).
8) coupled to the fifth digital control signal of the plurality of digital control signals, wherein the direct current is applied to the adjusted substantially linear current versus temperature change to be adjusted to direct current. A plurality of adjustable current mirrors for generating a temperature-dependent current, and an output terminal of the current level adjustment means (28) and an output terminal of the plurality of adjustable current mirrors, the temperature adjusted to the direct current. A load resistor (32) for generating an analog control voltage in response to the dependent current; and a load coupled to an output of the load resistor (32) for generating the analog control voltage, the peak being during a transition period between a plurality of operating temperature segments. A filter (34) for limiting phase displacement and coupling the analog control voltage to the varactor (36) to compensate for the temperature of the crystal oscillator over an operating temperature range. Temperature compensation circuit (1
0).