JP2003234618A - Frequency adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frequency adjusting method capable of adjusting the standard value (allowable error) of a clock frequency to be within the standard value at a reference temperature without managing a temperature inside a plant at all. <P>SOLUTION: In the frequency adjusting method, a change rate α (T) of the clock frequency f for a temperature change from the reference temperature T<SB>0</SB>to ambient temperature T is obtained on the basis of the correlation of the clock frequency f of an oscillation circuit and ambient temperature T (steps S1 and S2), the standard value A<SB>0</SB>at the reference temperature T<SB>0</SB>is converted to the standard value A (T=10°C) at actual ambient temperature T (10°C, for instance) on the basis of the change rate α (T) (steps S3 and S4), the daily rate error δf of the clock frequency f is detected under actual ambient temperature T (=10°C) and the characteristic value of the circuit element of the oscillation circuit 3 is adjusted so as to settle the detected daily rate error δf within the standard value A (T=10°C) at the actual ambient temperature T (=10°C) (step S5). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency adjusting method for adjusting a clock frequency used for a timepiece function mounted on a unit.

[0002]

2. Description of the Related Art Normally, when manufacturing and shipping a unit equipped with a clock function, a daily error of the clock frequency used for the clock function (error per day) is set at a reference temperature of 25 ° C.
In order to fit within the standard value (tolerance of daily error) in
The clock frequency needs to be adjusted.

Conventionally, the clock frequency is adjusted by measuring the clock frequency at a reference temperature of 25 ° C. to detect a daily error, and checking whether the daily error is within the standard value at the reference temperature. Check and if it is not within the standard value, adjust the characteristic value of the circuit element of the oscillation circuit that oscillates the clock frequency,
Alternatively, the clock function is corrected by software to adjust the daily error of the clock frequency within the standard value.

[0004]

Since the circuit element of the oscillation circuit usually has temperature characteristics, the oscillation frequency (clock frequency) of the oscillation circuit changes according to the ambient temperature.

Generally, when the clock frequency is adjusted in a factory, even if the temperature in the factory is set to a reference temperature of 25 ° C., the temperature in the factory will be different from the reference temperature of 25 ° C. depending on the place in the factory and the season. Variation occurs. The oscillation frequency of the oscillation circuit changes due to this temperature variation, and in order to prevent this change from affecting the accuracy of the clock frequency adjustment, normally when adjusting the clock frequency in the factory, It is necessary to strictly control the temperature of the above, to eliminate the temperature variation as much as possible, and to sufficiently secure the accuracy of the clock frequency adjustment.

However, in order to strictly control the temperature in the factory and eliminate variations in the temperature as much as possible, it is necessary to install a temperature management device in the factory, which is disadvantageous in terms of cost. Further, in such a case, there is a drawback that the accuracy of adjusting the clock frequency is restricted by the temperature control in the factory.

Therefore, the object of the present invention is to adjust the daily error of the clock frequency within the standard value at the reference temperature without controlling the temperature in the factory at all, and to obtain a high day error accuracy. It is to provide a frequency adjustment method that can be performed.

[0008]

In order to solve the above-mentioned problems, the present inventor found out the temperature characteristic of the circuit element that determines the clock frequency (that is, the correlation between the oscillation frequency of the oscillation circuit and the ambient temperature). That is, the ambient temperature can be easily detected by a temperature sensor or the like, and the inventors have proceeded with a study on whether or not can be used for adjusting the original clock, and arrived at the present invention.

That is, according to the first aspect of the invention, the change characteristic of the oscillation frequency of the oscillation circuit with respect to the temperature change of the ambient temperature is obtained, and the allowable error at the reference temperature is set to the predetermined ambient temperature based on the change characteristic. Converted to a permissible error at the predetermined ambient temperature, to detect the day difference error of the transmission frequency, so that the detected day difference error falls within the permissible error at the predetermined ambient temperature, The characteristic value of the circuit element of the oscillation circuit is adjusted.

According to a second aspect of the present invention, the allowable error at the predetermined ambient temperature is the rate of change of the oscillation frequency with respect to the temperature change from the reference temperature to the predetermined ambient temperature and the reference temperature. It is given by the product of the tolerance.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram of a main part of a unit equipped with a timepiece function, and FIG. 2 is a diagram explaining a procedure of a frequency adjusting method according to an embodiment of the present invention.

The frequency adjusting method according to this embodiment is
Referring to FIG. 1, based on the correlation between the oscillation frequency f of the oscillation circuit 3 in the unit 1 and the ambient temperature T, the reference temperature T0
The rate of change α (T) of the oscillation frequency f with respect to the temperature change from (for example, 25 ° C.) to a predetermined ambient temperature (here, the actual ambient temperature) T is calculated, and the reference temperature T0 is calculated based on the rate of change α (T). The standard value A0 at the specified ambient temperature T is converted into the standard value A (T) at the predetermined ambient temperature T, and
The daily difference error δf of the oscillation frequency f is detected, and the characteristic value of the circuit element of the oscillation circuit 3 is adjusted so that the detected daily difference error δf falls within the standard value A (T) at a predetermined ambient temperature T. To do.

First, the unit 1 used as an example will be described. The unit 1 is, for example, a device equipped with a clock function, and as the clock function, for example, an oscillation circuit 3 that transmits a clock frequency f, a clock CPU 5 that keeps time based on the clock frequency f that the oscillation circuit 3 transmits, and a clock. The CPU 5 includes a display unit 7 such as an LCD for displaying the time engraved by the CPU 5.

The oscillator circuit 3 includes, for example, a crystal oscillator X1 having a crystal piece 9 having a natural frequency fr, a variable capacitor Cv such as a trimmer, and a fixed capacitor C2 such as ceramic.
And C3. Fixed capacitors C2 and C3
Are respectively interposed between the respective ends of the crystal unit X1 and the ground point. The variable capacitor Cv is the fixed capacitor C2.
Are connected in parallel. Both ends of the crystal unit X1 have a clock C
It is connected to PU5 and the clock CPU is connected through this connection.
The voltage is supplied from 5 and the clock frequency f is oscillated to the clock CPU.

In this oscillator circuit 3, capacitors Cv and C are used.
2, 2 and C3 form the load capacitance CL of Expression 1. Due to this load capacitance CL, the natural frequency fr of the crystal blank 9 is calculated by the formula 2
According to the above, the clock frequency f is modulated and the clock CPU 5 oscillates.

[0016]

[Equation 1]

[0017]

[Equation 2]

Incidentally, C0 and C1 in the equation 2 respectively represent a parallel capacitance and an equivalent series capacitance which are equivalent constants of the crystal unit X1.

Generally, Cv, C2, C3 and fr have temperature characteristics. For example, Cv is a few hundred pp in the case of a trimmer.
m / ° C has a capacity-temperature characteristic, and C2 and C3, in the case of ceramic, have a capacity-temperature characteristic of ± several tens ppm / ° C, and f
r is −0. It has a frequency-temperature characteristic of 0 ppm / (° C) ² . Therefore, f generally has a frequency temperature characteristic.

In this oscillator circuit 3, as can be seen from equations 1 and 2, the clock frequency f oscillated by the oscillator circuit 3 is adjusted by adjusting the capacitance of the variable capacitor Cv.

The clock CPU 5 has a clock output pin 10
The clock frequency f from the oscillator circuit 3 is set to N
The frequency is divided (for example, N = 512) (that is, f / N) and output from the clock output pin 10.

Next, based on FIG. 2, by the frequency adjusting method according to the present invention, the daily difference error δf of the clock frequency f used for the timepiece function of the unit 1 is set under the ambient temperature T at the reference temperature T0 ( = 25 ° C), the procedure for adjusting the value within the expected value A0 will be described.

In step S1, the equation f = f (T) of the correlation between the oscillation frequency (clock frequency) f of the oscillation circuit 3 and the ambient temperature T is obtained based on the equations 1 and 2. Specifically, for Eqs. 1 and 2, the measured values are substituted into the equivalent constants C0 and C1, and the capacitors Cv, C2 and
C3 is a correlation expression Cv = Cv (T), C2 = C2 of the capacity-temperature characteristic obtained from the correlation diagram of the capacity-temperature characteristics.
(T), C3 = C3 (T) are substituted, and the correlation frequency fr = fr (T) of the frequency temperature characteristic obtained from the correlation of the frequency temperature characteristic is substituted for the natural frequency fr of the crystal blank 9. ,
Find f = f (T).

In step S2, the equation f = f for the correlation between the oscillation frequency f obtained in step S1 and the ambient temperature T
Based on (T), the rate of change α (T) of the oscillation frequency f with respect to the temperature change from the reference temperature T0 to the ambient temperature T is calculated from the equation (3).
Ask for.

[0025]

[Equation 3]

When the capacitors Cv, C2 and C3 are invariant with respect to the ambient temperature T, or can be approximated to invariant, the rate of change α (T) is expressed by Equation 4, and the natural vibration of the crystal piece 9 is expressed by It is represented by the correlation expression fr (T) of the frequency temperature characteristic of several fr.

[0027]

[Equation 4]

Since the rate of change α (T) in this case coincides with the frequency deviation Δfr / fr of the natural frequency fr of the crystal blank 9 disclosed by the manufacturer, in such a case, step S
1 is omitted, and the frequency deviation Δfr /
You may use fr. Incidentally, the frequency deviation Δfr / fr when the crystal piece 9 is a tuning fork type is given by Equation 5 as an example.

[0029]

[Equation 5]

In step S3, the standard value A0 at the reference temperature T0 is converted into the standard value A (T) at the ambient temperature T based on the rate of change α (T) obtained in step S2.
Here, as shown in Equation 6, the standard value A at the reference temperature T0
The product of 0 and the rate of change α (T) gives the standard value A (T) at the ambient temperature T.

[0031]

[Equation 6]

Therefore, when the change rate α (T) is given by the equation 5, the standard value A (T) is given by the equation 7.

[0033]

[Equation 7]

In step S4, the actual ambient temperature T is measured, and the measured value is substituted into the standard value A (T) of the equation 6 obtained in step S3 to obtain the standard value A at the actual ambient temperature T.
Calculate (T). For example, the actual ambient temperature T = 10
° C, reference temperature T0 = 25 ° C, reference value A0 = 32.768
In the case of kHz / 512 frequency division = 64 Hz, the standard value A (T) in the case of Formula 7 is A (T = 10 ° C.) = 63.99991.
Hz ± 5 ppm. Here, ± 5 ppm represents other errors. The reference value A0 is a value divided by N (N = 512) division in accordance with the output (clock frequency f divided by N) of the clock output pin 10 of the clock CPU 5.

In this frequency adjustment method, the daily difference error δf of the clock frequency f detected under the actual ambient temperature T (= 10 ° C.) is defined as the standard value A at the actual ambient temperature T (= 10 ° C.). By keeping the temperature within (T), the reference temperature T0 (= 25
Error of the clock frequency f detected under
Becomes within the standard value A0 at the reference temperature T0.

In step S5, the actual ambient temperature T (=
The clock frequency f is adjusted under 10 ° C. That is, under the actual ambient temperature T (= 10 ° C), the clock CPU
The output of the clock output pin 10 of No. 5 is measured to detect the daily difference error δf of the clock frequency f.
Check whether it is within the temperature range), and specify the standard value A (T = 10 ℃)
If it is not within the range, that is, if δf> A (T = 10 ° C),
By adjusting the variable capacitor Cv of the oscillator circuit 3, the daily difference error δf of the detected clock frequency f becomes the standard value A (T = 10
C.), that is, .delta.f.ltoreq.A (T = 10.degree. C.).

As a result, the daily difference error δf of the clock frequency f under the reference temperature T0 (= 25 ° C.) becomes the reference temperature T0.
It falls within the standard value A0 in.

As described above, according to this frequency adjusting method, the standard value A0 at the reference temperature T0 is changed to the standard value A (T) at the predetermined ambient temperature (here, the actual ambient temperature) T.
And the daily difference error δf of the clock frequency f detected under the predetermined ambient temperature T is kept within the standard value A (T) at the predetermined ambient temperature T. The daily error δf of the detected clock frequency f is the reference temperature T
Since it falls within the standard value A0 at 0, the temperature error in the factory is not controlled, and the daily difference error δf of the clock frequency f is set at the reference temperature T0 under a predetermined ambient temperature T. It can be adjusted within the standard value A0.

Further, since the accuracy of adjusting the clock frequency is not restricted by the temperature management in the factory, it is possible to realize a high day difference accuracy without being restricted by the temperature in the factory.

Further, from the reference temperature T0 to the predetermined ambient temperature T
Since the standard value A (T) at the predetermined ambient temperature T is given by the product of the rate of change α (T) of the oscillation frequency f with respect to the temperature change and the standard value A0 at the reference temperature T0, The standard value A (T) can be obtained.

In this embodiment, step S1
In the above, the case where the equation f = f (T) for the correlation between the oscillation frequency f of the oscillator circuit 3 and the ambient temperature T is obtained has been described, but when it is difficult to obtain the equation f = f (T) for the correlation. May be obtained as a graph, and in step S2, the rate of change α (T) may be obtained based on this graph.

[0042]

According to the first aspect of the present invention, the oscillating frequency detected under the predetermined ambient temperature is calculated by converting the permissible error at the reference temperature into the permissible error at the predetermined ambient temperature. By keeping the daily error of the error within the permissible error at the specified ambient temperature, the daily error of the oscillation frequency detected under the reference temperature can be within the permissible error at the reference temperature. Therefore, the daily error of the oscillation frequency can be adjusted within the allowable error of the reference temperature under a predetermined ambient temperature without controlling the temperature in the factory.

Further, since the precision of the adjustment of the oscillation frequency is not restricted by the temperature control in the factory, it is possible to realize a high day difference accuracy without being restricted by the temperature in the factory.

According to the second aspect of the present invention, the product of the rate of change of the oscillation frequency with respect to the temperature change from the reference temperature to the predetermined ambient temperature and the allowable error in the reference temperature is used to determine the predetermined ambient temperature. Since the tolerance is given, the tolerance at a predetermined ambient temperature can be easily obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part of a unit equipped with a timepiece function according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a frequency adjusting method according to an embodiment of the present invention.

[Explanation of symbols]

3 oscillator circuits α (T) change rate A (T) Standard value at ambient temperature T Standard value at A0 reference temperature T0 Cv variable capacitor f Oscillation frequency of oscillation circuit T Ambient temperature T0 reference temperature

Claims (2)

[Claims] 1. A change characteristic of an oscillation frequency of an oscillation circuit with respect to a change in ambient temperature is obtained, and based on the change characteristic,
The permissible error at the reference temperature is converted into the permissible error at the predetermined ambient temperature, the daily difference error of the transmission frequency is detected under the predetermined ambient temperature, and the detected daily difference error is determined by the predetermined error. A frequency adjusting method characterized in that the characteristic value of a circuit element of the oscillation circuit is adjusted so as to be within an allowable error in ambient temperature. 2. The allowable error at the predetermined ambient temperature is the product of the rate of change of the oscillation frequency and the allowable error at the reference temperature with respect to the temperature change from the reference temperature to the predetermined ambient temperature. The frequency adjusting method according to claim 1, wherein the frequency adjusting method is provided.