JP2001044759A - Reference clock frequency temperature control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reference clock frequency temperature control circuit that efficiently acquires a control voltage in response to the ambient temperature at the start of a device so as to reduce a frequency error due to a temperature characteristic of a reference clock when power is applied to the device. SOLUTION: A CPU 40 receiving temperature information from a temperature detection circuit 50 reads control voltage information suitable for temperature from a storage circuit 60 on the basis of the temperature information and gives the control voltage information to a control voltage generating circuit 30. Since the control voltage generating circuit 30 generates a control voltage on the basis of the control voltage information and a reference clock generator 20 generates a reference clock with a desired frequency on the basis of the control voltage, the control circuit can efficiently acquire the control voltage in response to the ambient temperature when power is applied to a device and can reduce a frequency error due to a temperature characteristic of the reference clock at the start of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reference clock frequency temperature control circuit, and more particularly to a reference clock frequency temperature control circuit for generating a reference clock having a desired frequency by adjusting a control voltage according to an ambient temperature. .

[0002]

2. Description of the Related Art When a power supply of a device is turned on, a reference voltage having a desired frequency is obtained by applying a constant voltage as a control voltage of a reference clock generator such as a temperature compensated crystal oscillator (TCXO). Usually, the desired frequency is T
This is a designated frequency such as CXO. In this case, if the ambient temperature is biased toward high or low temperature, the control voltage will deviate from the desired frequency even if a constant voltage is applied. If the temperature characteristics of the TCXO itself require accuracy, there is a problem that the TCXO becomes expensive. Further, in the case of a system using the CDMA system, if there is a frequency error in the TCXO serving as a reference clock of the device, a detection error occurs due to a chip unit shift caused by the frequency error and frame synchronization cannot be achieved. there were.

[0003] As a conventional reference clock frequency temperature control circuit, there is known a reference clock frequency temperature control circuit disclosed in Japanese Patent Application Laid-Open No. 6-252624. This reference clock frequency temperature control circuit includes a memory storing correction data for correcting the characteristic of the oscillation frequency of the crystal oscillator with respect to a temperature change, and reads the correction data from the memory according to the peripheral temperature of the crystal oscillator, A control voltage corrected based on the correction data is supplied to the crystal unit. Further, as a technique for performing frequency compensation for a temperature change, techniques such as Japanese Patent Application Laid-Open No. Hei 7-202568 and Japanese Patent No. 27132214 are disclosed.

[0004]

However, in the above-mentioned prior art, it is not possible to reduce the frequency error of the reference clock pulse generated due to the fluctuation of the ambient temperature when the device is started up.

Further, the reference clock frequency temperature control circuit disclosed in Japanese Patent Application Laid-Open No. 6-252642 aims at simplifying the circuit configuration inside the TCXO, but it is difficult to achieve high-precision temperature characteristics at low cost. is there. Furthermore, in the temperature compensating devices disclosed in Japanese Patent Application Laid-Open No. 7-202568 and Japanese Patent No. 27132214, no voltage information table is used, and no reference is made to clock generation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and efficiently obtains a control voltage corresponding to an ambient temperature when a power supply of a device is turned on, and uses a temperature characteristic of a reference clock when the power supply of the device is turned on. An object of the present invention is to provide a reference clock frequency temperature control circuit capable of reducing a frequency error.

[0007]

In order to achieve the above object, an invention according to claim 1 is a reference clock generator for generating a reference clock having a predetermined frequency in accordance with a supplied control voltage, and the reference clock generator. A temperature detection circuit for detecting a peripheral temperature of the generator and outputting temperature information, and a control voltage required for generating a reference clock having a predetermined frequency by the reference clock generator under each peripheral temperature. A control required to generate a reference clock having a desired frequency with reference to a storage circuit storing a voltage information table, temperature information output from the temperature detection circuit, and a voltage information table stored in the storage circuit And a control voltage supply circuit for supplying a voltage to the reference clock generator.

That is, when the temperature detection circuit detects the peripheral temperature of the reference clock generator and outputs temperature information, the control voltage supply circuit acquires the output temperature information. Further, the control voltage supply circuit obtains a voltage information table stored in a storage circuit indicating a control voltage necessary for generating a reference clock having a predetermined frequency by the reference clock generator under each ambient temperature. I do.

The control voltage supply circuit refers to the acquired temperature information and the voltage information table, and supplies a control voltage necessary for generating a reference clock having a desired frequency to the reference clock generator. Then, the reference clock generator generates a reference clock having a predetermined frequency according to the supplied control voltage.

The reference clock generator only needs to generate a reference clock having a predetermined frequency in accordance with the supplied control voltage, and the invention in claim 2 is an example of the configuration. In the reference clock frequency temperature control circuit, the reference clock generator is constituted by a temperature compensated crystal oscillator.

That is, the control voltage supply circuit refers to the acquired temperature information and the voltage information table, and supplies a control voltage required to generate a reference clock having a desired frequency to the temperature-compensated crystal oscillator. Then, the temperature compensated crystal oscillator generates a reference clock having a predetermined frequency according to the supplied control voltage.

The temperature detecting circuit only needs to detect the peripheral temperature of the reference clock generator and output the temperature information. The invention according to claim 3 is an example of the timing for detecting the peripheral temperature. Alternatively, in the reference clock frequency temperature control circuit according to claim 2, the temperature detection circuit is configured to detect an ambient temperature when the power is turned on.

That is, when the power supply is turned on, the temperature detection circuit detects the peripheral temperature of the reference clock generator and outputs temperature information. As described above, when the ambient temperature is detected using the rise of the power supply as a trigger, the frequency of the reference clock at the time of the rise can be controlled with a simple configuration, but at least the ambient temperature of the reference clock generator can be detected. From the viewpoint that it is preferable, it is possible to adopt a configuration in which the user can instruct the detection of the ambient temperature as needed.

The storage circuit only needs to store a voltage information table indicating a control voltage required for generating a reference clock having a predetermined frequency by the reference clock generator at each ambient temperature. It may be a hard disk or a floppy disk. The control voltage supply circuit refers to the temperature information output from the temperature detection circuit and the voltage information table stored in the storage circuit, and generates a control voltage required to generate a reference clock having a desired frequency. As an example of a specific configuration, the invention according to claim 4 is a reference clock frequency temperature control circuit according to any one of claims 1 to 3, wherein the control voltage supply circuit is A CPU that obtains control voltage information necessary to generate a reference clock having a desired frequency with reference to the temperature information and the voltage information table, and a predetermined voltage based on the control voltage information obtained by the CPU. And a control voltage generation circuit that generates a control voltage and supplies the control voltage to a reference clock generator.

That is, when the CPU refers to the temperature information and the voltage information table and obtains control voltage information necessary for generating a reference clock having a desired frequency,
The control voltage generation circuit generates a predetermined control voltage based on the control voltage information acquired by the CPU, and supplies the control voltage to the reference clock generator.

Further, as a configuration example of the control voltage generation circuit,
According to a fifth aspect of the present invention, in the reference clock frequency temperature control circuit according to the fourth aspect, the control voltage generation circuit comprises:
It is composed of a digital / analog conversion circuit. That is, the digital / analog conversion circuit generates a predetermined control voltage by performing digital / analog conversion on the control voltage information acquired by the CPU, and supplies the generated control voltage to the reference clock generator.

The voltage information table stored in the storage circuit may be always referred to by the control voltage supply circuit or may be referred to only when a predetermined condition is satisfied. good. As an example of the configuration of the control voltage supply circuit in the latter case, the invention according to claim 6 is the reference clock frequency temperature control circuit according to any one of claims 1 to 5, wherein When the ambient temperature is outside the predetermined temperature range, a voltage information table stored in the storage circuit is referred to. That is, the control voltage supply circuit refers to the voltage information table stored in the storage circuit only when the ambient temperature based on the temperature information is not within the predetermined temperature range.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main configuration of a reference clock frequency temperature control circuit according to an embodiment of the present invention.

The reference clock frequency temperature control circuit 10 is provided with a reference clock generator 20 for generating a reference clock. The reference clock generator 20 generates a control voltage and supplies the control voltage to the reference clock generator 20. A control voltage generating circuit 30 that can be supplied is connected. The control voltage generation circuit 30 is connected to a CPU 40, and the control voltage generation circuit 30 generates a control voltage according to a control instruction from the CPU 40.

A temperature detecting circuit 50 is arranged near the reference clock generator 20 to detect the temperature around the reference clock generator 20. Further, the CPU 40 is connected to a storage circuit 60 that stores, as a voltage information table, control voltage information necessary for the reference clock generator 20 to output a desired frequency for each ambient temperature.

In the reference clock generator 20, since the frequency characteristic of the reference clock generated by the change in the ambient temperature changes, the reference clock frequency temperature control circuit 10 controls the frequency of the reference clock by the above-described configuration. are doing. That is, the temperature detection circuit 50 detects the temperature around the reference clock generator 20 and outputs the temperature information to the CPU 4.
0, the CPU 40 obtains control voltage information appropriate for the temperature at power-on from the voltage information table based on the temperature information, and outputs the control voltage information to the control voltage generation circuit 3.
0 to the control voltage generation circuit 30
To supply.

The control voltage generation circuit 30 generates a control voltage from the control voltage information and supplies the control voltage to the frequency control terminal of the reference clock generator 20. Therefore, the CPU 40 that obtains appropriate control voltage information from the voltage information table and the control voltage generation circuit 30 that generates a control voltage from the control voltage information and supplies the control voltage to the reference clock generator 20 are, in this sense, the present invention. And a control voltage supply circuit.

FIG. 2 is a block diagram showing an example of a specific configuration of the reference clock frequency temperature control circuit 10. As shown in FIG.
As shown in FIG. 2, the CPU 40 includes a temperature detection circuit 50.
A temperature sensor 51 and an A / D conversion circuit 52 as
A D / A conversion circuit 31 as a control voltage generation circuit 30 is connected. The D / A conversion circuit 31 has a temperature-compensated crystal oscillator (TC
XO) 21 is connected. Also, the CPU 40 includes:
A nonvolatile memory 61 as a storage circuit 60 is connected.

With such a configuration, when the temperature sensor 51 detects the ambient temperature of the TCXO 21, the A / D conversion circuit 52 converts the detected ambient temperature from analog to digital and supplies it to the CPU 40. The CPU 40 acquires control voltage information appropriate for the temperature at power-on from the voltage information table stored in the nonvolatile memory 61 based on the detected ambient temperature.

Then, the control voltage information is transferred to the D / A conversion circuit 3.
1, the D / A conversion circuit 31 generates a control voltage by performing digital / analog conversion of the control voltage information, and supplies the control voltage to the TCXO 21. Then, TCXO21
Generates a reference clock having a desired frequency based on the supplied control voltage.

Next, the operation of the reference clock frequency temperature control circuit according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, as soon as the power is turned on, the temperature detection circuit 50 detects the peripheral temperature of the reference clock generator 20 and supplies temperature information to the CPU 40 (steps S100 and S110). The number of bits of the temperature information is increased when the temperature of the frequency of the reference clock generator 20 fluctuates greatly.

The CPU 40 reads control voltage information suitable for the temperature from the storage circuit 60 based on the temperature information (step S120). The storage circuit 60 has a table in which temperature information is used as an address and control voltage information for outputting a desired frequency by the reference clock generator 20 for each temperature is used as data. The CPU 40 supplies the read control voltage information to the control voltage generation circuit 30 (Step S130).

At this time, the CPU 40 converts the control voltage information so as to match the input format (serial data or parallel data) of the control voltage generation circuit 30. The control voltage generation circuit 30 supplies the control voltage generated based on the control voltage information to the frequency control terminal of the reference clock generator 20, and the frequency of the reference clock generator 20 is determined (Step S140). After this, AFC (Automatic
Frequency Control) control is performed, and the reference clock frequency is synchronized with the received signal (step S150).

FIG. 4 shows an error characteristic of the reference clock frequency with respect to a temperature change on the horizontal axis. As an example, CD
In the case of the MA system, when the frequency error shown in FIG.
A is a characteristic when a predetermined constant voltage is applied to the control terminal of the reference clock generator 20. A frequency error of about ± Y1 occurs due to a temperature change, and frame synchronization cannot be achieved depending on the temperature. B is a characteristic when temperature control is performed in the present embodiment, and the frequency error is ±
The level can be reduced to a level that does not cause a problem in frame synchronization while keeping the frame length within Y3. Where | Y1 |> | Y2
|> | Y3 |.

In the present embodiment, the voltage information table stored in the storage circuit always refers to the voltage information table stored in the storage circuit by the control voltage supply circuit, but only when necessary. Can also be referred to. The operation in this case will be described with reference to FIG. As soon as the power supply is turned on, the temperature detection circuit 50 detects the temperature around the reference clock generator and outputs the temperature information to C.
It is supplied to the PU 40 (steps S200, S210).

Then, the CPU 40 checks whether or not the ambient temperature based on the supplied temperature information is within a predetermined temperature range (step S220). When the ambient temperature is within the predetermined temperature range, the CPU 40 controls the normal control voltage generation instruction without referring to the voltage information table stored in the storage circuit 60, that is, without performing temperature control of the frequency. The voltage is supplied to the voltage generation circuit 30 (step S230). The control voltage generation circuit 30 generates a control voltage based on a normal control voltage generation instruction, and supplies the control voltage to the reference clock generator 20 (step S260).

On the other hand, if the ambient temperature is not within the predetermined temperature range, the CPU 40 reads control voltage information suitable for the temperature from the storage circuit 60 based on the temperature information, as in the present embodiment (step S240). ), And supplies the read control voltage information to the control voltage generation circuit 30 (step S250). The control voltage generation circuit 30 supplies the control voltage generated based on the control voltage information to the reference clock generator 20 (Step S260). Thereafter, AFC control is performed, and the reference clock frequency is synchronized with the received signal (step S270).

As described above, when the temperature information is supplied from the temperature detecting circuit 50, the CPU 40 reads out the control voltage information suitable for the temperature from the storage circuit 60 based on the temperature information and supplies it to the control voltage generating circuit 30. The control voltage generation circuit 30 generates the reference voltage having a desired frequency based on the control voltage, and the reference clock generator 20 efficiently generates the control voltage according to the ambient temperature. It becomes possible to acquire.

[0034]

As described above, the present invention can provide a reference clock frequency temperature control circuit capable of efficiently obtaining a control voltage corresponding to the ambient temperature.
According to the second aspect of the present invention, the frequency of the reference clock generated by the temperature-compensated crystal oscillator can be temperature-controlled.

Further, according to the invention of claim 3,
When the power is turned on, the surrounding temperature is detected, and the frequency of the reference clock can be temperature-controlled based on the surrounding temperature. Further, according to the fourth aspect of the present invention, since a normally used circuit such as a CPU can be used, it is not necessary to newly provide an additional configuration, and the cost can be reduced.

Further, according to the invention of claim 5,
The control voltage information based on the voltage information table can be converted by a simple circuit to generate the control voltage of the reference clock generator. Further, according to the invention of claim 6,
Since the voltage information table can be used only when the temperature control of the reference clock is required, the control voltage can be efficiently supplied to the reference clock generator.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main configuration of a reference clock frequency temperature control circuit according to an embodiment.

FIG. 2 is a block diagram illustrating an example of a specific configuration of a reference clock frequency temperature control circuit.

FIG. 3 is a flowchart showing an operation procedure in the reference clock frequency temperature control circuit.

FIG. 4 is a graph showing an error characteristic of a reference clock frequency with respect to a temperature change.

FIG. 5 is a flowchart showing an operation procedure of a reference clock frequency temperature control circuit in a modified example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Reference clock frequency temperature control circuit 20 Reference clock generator 21 Temperature compensated crystal oscillator (TCXO) 30 Control voltage generation circuit 31 D / A conversion circuit 40 CPU 50 Temperature detection circuit 51 Temperature sensor 52 A / D conversion circuit 60 Storage circuit 61 Non-volatile memory

Claims (6)

[Claims] A reference clock generator for generating a reference clock having a predetermined frequency in accordance with a supplied control voltage; a temperature detection circuit for detecting a peripheral temperature of the reference clock generator and outputting temperature information; A storage circuit for storing a voltage information table indicating a control voltage necessary for the reference clock generator to generate a reference clock having a predetermined frequency under each ambient temperature; and a memory output from the temperature detection circuit. A control voltage supply circuit for supplying a control voltage required for generating a reference clock having a desired frequency to the reference clock generator with reference to temperature information and a voltage information table stored in the storage circuit. A reference clock frequency temperature control circuit, comprising: 2. The reference clock frequency temperature control circuit according to claim 1, wherein said reference clock generator is a temperature-compensated crystal oscillator. 3. The reference clock frequency temperature control circuit according to claim 1, wherein the temperature detection circuit detects a peripheral temperature at power-on. circuit. 4. The reference clock frequency temperature control circuit according to claim 1, wherein the control voltage supply circuit refers to the temperature information and the voltage information table to determine a desired frequency. CPU that obtains control voltage information necessary to generate reference clock
And a control voltage generation circuit that generates a predetermined control voltage based on the control voltage information acquired by the CPU and supplies the control voltage to the reference clock generator. 5. The reference clock frequency temperature control circuit according to claim 4, wherein said control voltage generation circuit is a digital / analog conversion circuit. 6. The reference clock frequency temperature control circuit according to claim 1, wherein the control voltage supply circuit is configured to control when a peripheral temperature based on the temperature information is outside a predetermined temperature range. A reference clock frequency temperature control circuit, which refers to a voltage information table stored in the storage circuit.