CN2511047Y

CN2511047Y - Microcomputer temperature-compensated crystal oscillator

Info

Publication number: CN2511047Y
Application number: CN 01273470
Authority: CN
Inventors: 于军; 高俊雄; 刘刚; 喻骞宇; 王耘波; 周文利; 谢基凡
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2001-12-20
Filing date: 2001-12-20
Publication date: 2002-09-11
Anticipated expiration: 2011-12-20

Abstract

The utility model discloses a micro-machine temperature compensation crystal oscillator, comprising a temperature measuring circuit, an 8 bit or more than 8 bit single chip machine, a filter circuit and a pressure control crystal oscillator connected in order. The single chip machine includes a PWM square-wave module which is transferred to the filter circuit. The filter circuit outputs the dc towards the pressure control crystal oscillator to control the pressure. The measurement circuit can use the digital temperature senor, and the crystal oscillator comprises a phase inverter, a triode or a special oscillator chip plate. The utility model takes advantages of high product efficiency, good productivity; achieving the whole automatic adjustment and the correction; low producing cost; and good product reliability. The utility model can also use the batch on-line programming mode to do the slight adjustment for the frequency and the diameter to the MCXO with correction MCXO in whole automatic, in scale and high speed.

Description

A kind of microcomputer temperature compensating crystal oscillator

Technical field

The utility model belongs to field of electronic devices, relates to a kind of temperature compensating crystal oscillator (MCXO), particularly a kind of small size microcomputer temperature compensating crystal oscillator.

Background technology

Temperature compensating crystal oscillator is the class oscillator that frequency stability is only second to constant-temperature crystal oscillator.Difference by its temperature compensation is divided into two kinds of crystal oscillator of analog temperature compensation and digital temperature compensation crystal oscillistors again.Outstanding feature such as they have all that volume is little, in light weight, power consumptive province, start characteristic are good, though its frequency stability and temperature frequency difference are than low 1～3 order of magnitude of constant-temperature crystal oscillator, but, use very extensive in, the consumer electronic device military at communication, navigation, Aero-Space, stored-program control exchange, all purpose instrument etc. than high 1～3 order of magnitude of common simple crystal oscillator.

The common simulation compensated crystal oscillator uses the thermistor network to produce temperature-compensated voltage, if the resistor network parameter can be an ideal value fully, the frequency temperature deviation of temperature compensating crystal oscillator can compensate in very wide temperature range and reach 1ppm, it is very big that but the effect temperature compensation of crystal oscillator is influenced by thermistor and fixed resistance value, even the employing precision is ± 1% resistance, produce a collection of TCXO, the max value of error of their frequency temperature deviation also can surpass ± 2ppm, therefore to guarantee rate of finished products, just must measure each resistance and calculate respectively, but when producing temperature compensating crystal oscillator in enormous quantities, be impossible measure each components and parts.Therefore productibility and rate of finished products become a great contradiction.

In addition, even all resistance elements are all very desirable, the analog compensation mode also has the limit, and it is not good for the compensation effect of wide temperature range, and can't the compensating frequency trip point and the crystal resonator of non-three frequency temperature curves.

Above problems can only be solved with the mode of digital temperature compensation.But no matter be the temperature-compensating of ordinary numbers formula or the crystal oscillator of original most of microcomputer temperature-compensating, all to use various logic and sequence circuit chip, D/A converter or such as 8051 Series chip, their volume is all quite big.Therefore want miniaturization, unlikely again reduction performance must adopt minitype paster formula single-chip microcomputer and companion chip, and the conventional thought of radical change simultaneously replaces with new circuit.

The utility model content

The purpose of this utility model is to provide a kind of novel microcomputer temperature compensating crystal oscillator, and this crystal oscillator can not only overcome the existing defective of analog compensation mode, and volume is little, rate of finished products is high, and has good compensation performance.

For realizing above-mentioned utility model purpose, a kind of microcomputer temperature compensating crystal oscillator, form by the temperature measurement circuit that links to each other successively, single-chip microcomputer, filter circuit and the VCXO more than 8 or 8, it is characterized in that: described single-chip microcomputer comprises PWM square wave module, described single-chip microcomputer is to described filter circuit output PWM square wave, and described filter circuit is to described VCXO output direct-current control voltage.

Described temperature measurement circuit can adopt digital temperature sensor, and described crystal oscillator can be made of inverter, triode or special-purpose vibration chip.The utility model also can be provided with the RS232 interface, and the In of this interface and Out are connected on respectively on two ports of described single-chip microcomputer

The utility model is at the contradiction of analog compensation mode productibility and rate of finished products, adopt digital thermometric chip to substitute temperature measurement circuit, the use one chip microcomputer of simulated temperature measurement components and parts and A/D converter composition, program and digital circuit with basic fixed realize MCXO, use batch online programming mode that MCXO is carried out frequency and parameter fine setting simultaneously, calibrate MCXO automatically, in enormous quantities, at high speed.So just improve productibility widely, also guaranteed rate of finished products.Use the output output PWM pulse-width modulation square wave of single-chip microcomputer, produce temperature-compensated voltage static state, no saltus step that voltage is continuous,, reach the saving cost, reduce the purpose of volume with this alternative D/A chip by filter circuit.

By trial production in batches, 20 properties of sample all reach designing requirement, and the main technical parameters of sample is as follows:

Nominal frequency: 4～32MHz

Frequently temperature characteristics :-40 ℃～+ 85 ℃ less than ± 1ppm

Frequency accuracy: less than ± 0.2ppm

Operating current: less than 30mA

Frequency trim scope: ± 10ppm

Operating voltage: 5V DC

Therefore can draw and the utlity model has: (1) manufacture a finished product rate height, productibility is good; (2) can realize full-automatic debugging and calibration; (3) production cost is low; (4) product reliability is good.

Description of drawings

Fig. 1 is the structural representation of the utility model microcomputer temperature compensating crystal oscillator;

Fig. 2 is a kind of embodiment schematic diagram of temperature measurement circuit among Fig. 1;

Fig. 3 is the another kind of embodiment schematic diagram of temperature measurement circuit among Fig. 1;

Fig. 4 is a kind of embodiment schematic diagram of filter circuit among Fig. 1;

Fig. 5 is a kind of embodiment schematic diagram of VCXO among Fig. 1.

Embodiment

As shown in Figure 1, the utility model is by 1,8 of temperature measurement circuits that link to each other successively or single-chip microcomputer 2, filter circuit 3 and the VCXO 4 more than 8, single-chip microcomputer 2 is to filter circuit 3 output PWM square waves, and described filter circuit 3 is to described VCXO 4 output direct-current control voltages.Each several part specifically is described below:

Temperature measurement circuit 1 mainly is that ambient temperature is converted into the voltage of analog form or the binary data of electric current and digital form as the circuit of induced environment temperature.Analog temperature sensor obtains being changed to the binary data that MCU (single-chip microcomputer) can discern by A/D converter behind temperature variant voltage, the electric current; Digital thermometric integrated circuit directly is converted into the discernible data of MCU to temperature data, and is read in by MCU.Using digital temperature sensor is characteristics of the present invention, if adopt the digital temperature sensing chip, as DS1820, just can directly the digital temperature sensing chip be linked to each other with single-chip microcomputer, exports digital temperature signal by the digital temperature sensing chip to single-chip microcomputer.Using digital temperature sensor is characteristics of the present invention, but the present invention also can use analog form to realize.As Fig. 2, shown in Figure 3, temperature measurement circuit shown in Figure 2 utilizes the simulated temperature measurement chip to realize, links to each other with single-chip microcomputer through A/D converter at the simulated temperature measurement chip.Temperature measurement circuit shown in Figure 3 is realized by artifical resistance, is made of resistance R 1, A/D converter and thermistor Rt, and A/D converter is exported digital temperature signal to single-chip microcomputer.

Single-chip microcomputer 2 is cores of MCXO, mainly carries out the calculating of reading, handle and control voltage of temperature data, and in order to guarantee computational speed and precision, single-chip microcomputer should be more than 8 at least, also can adopt 16 single-chip microcomputer.8 machines and 16 machines are compared, and speed is slow, and calculation procedure is complicated, but the pin of single-chip microcomputer will lack, to satisfy the requirement of miniaturization.

The PWM output module mainly is in order to realize D/A conversion, the D/A chip that alternative price is more expensive, volume ratio is bigger with minimum cost, minimum components and parts.The change of the duty ratio of PWM output square wave changes the voltage of wave network output after filtration thereupon, to reach the purpose of output direct current.

The purpose that 3 pairs of PWM output of filter circuit square wave carries out the filter network of filtering is a direct current with the PWM change in voltage exactly mainly, and the ripple voltage in this direct current is not impacted the stability of crystal oscillator.Filter network can be passive also can be active, the active power filtering effect is more much better than passive network, but structure wants complicated a lot.The II type filter network that the resistance of the common employing of filter circuit low-temperature coefficient as shown in Figure 4 and electric capacity are formed is converted into constant DC and presses, in order to carry out temperature-compensating the PWM square wave filtering of one-chip machine port output.

VCXO 4 is keys of output frequency, and its oscillating circuit has a variety of structures.As shown in Figure 5, VCXO is made of vibrate chip, crystal resonator Y1, variable capacitance diode D1 and capacitor C 1, C2, C3 of special use, crystal resonator Y1, capacitor C 3, variable capacitance diode D1 and capacitor C 1 are contacted successively and are formed the loop, special-purpose vibration chip is in parallel with crystal resonator Y1, and capacitor C 2 and capacitor C 3, variable capacitance diode D1 are in parallel.This oscillating circuit links to each other with filter circuit by resistance.

Above-mentioned VCXO also can adopt inverter or triode to realize.

For realizing online programming correction and frequency trim, can use RS232 interface and microcontroller communication, the In of com mouth and Out are connected on respectively on two ports of single-chip microcomputer.Like this, can omit trimmer, not re-use the method for manual adjustment frequency to nominal frequency.

Claims

1. microcomputer temperature compensating crystal oscillator, form by the temperature measurement circuit that links to each other successively, single-chip microcomputer, filter circuit and the VCXO more than 8 or 8, it is characterized in that: described single-chip microcomputer contains PWM square wave module, described single-chip microcomputer is to described filter circuit output PWM square wave, and described filter circuit is to described VCXO output direct-current control voltage.

2. microcomputer temperature compensating crystal oscillator according to claim 1 is characterized in that: described temperature measurement circuit is a digital temperature sensor.

3. microcomputer temperature compensating crystal oscillator according to claim 1 and 2 is characterized in that: this oscillator also has been arranged at the RS232 interface, and the In of this interface and Out are connected on respectively on two ports of described single-chip microcomputer.

4. microcomputer temperature compensating crystal oscillator according to claim 1 and 2 is characterized in that: described VCXO is made of vibrate chip, crystal resonator Y1, variable capacitance diode of special use.

5. microcomputer temperature compensating crystal oscillator according to claim 4 is characterized in that: described special-purpose vibration chip is substituted by inverter or triode.