JP3419920B2 - Digital temperature compensated piezoelectric oscillator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for compressing a memory capacity in a digital temperature compensated piezoelectric oscillator. 2. Description of the Related Art FIG. 2 shows a prior art in a system diagram. Compensation information corresponding to the temperature characteristic of the VCXO 13 is stored in the memory circuit 5 in advance, and the temperature information from the temperature sensor 1 is converted into an analog / digital conversion circuit 2 (hereinafter, referred to as an A / D conversion circuit) and stored as an address. Supply to circuit 5. The memory circuit 5 supplied with the address reads the corresponding compensation information. The compensation information read from the address is used as a digital / analog conversion circuit 12 (hereinafter, referred to as a D / A conversion circuit 12) to control the VCXO 13 to perform frequency temperature compensation. The basic configuration of this prior art is:
It is determined based on the specifications (operating temperature range, frequency tolerance, etc.) of the digital temperature-compensated piezoelectric oscillator, the temperature characteristics of the VCXO 13, and the like. First, as the capacity of the memory circuit (8 bits × 256), (8
8 bits of (bit × 256) represent the fineness of the temperature information for controlling the frequency of the VCXO 13. That is, the temperature range of the temperature characteristic inherent to the VCXO 13 can be stored with a fineness of 8 bits = 256. (8 bits x 25
256 of 6) represents the number of 8-bit compensation information. That is, it indicates the fineness of controlling the temperature compensation of the oscillation frequency in the operating temperature range of the digital temperature compensation piezoelectric oscillator. In the prior art, the number of bits of the A / D conversion circuit 2, the number of bits of the address of the memory circuit 5, and the address of the memory circuit 5 used in the digital temperature compensated piezoelectric oscillator are known. And the number of bits of the D / A conversion circuit 12 are the same. To increase the accuracy of the frequency compensation control with respect to temperature, the number of addresses of the memory circuit and the number of bits of the compensation information must be increased. As a result, the capacity of the memory circuit 5 must be increased, which leads to an increase in cost and an occupied area. There were challenges. In order to increase the accuracy of the temperature compensation control of the digital temperature compensation piezoelectric oscillator without increasing the capacity of the memory circuit 5, a known temperature control between two adjacent points of the temperature to be controlled is performed. By interpolating the control values using a simple average value, the temperature interval for performing the temperature compensation control was reduced to １ ／, thereby solving the problem. [0005] The frequency-temperature characteristic of a quartz plate generally draws a quadratic curve, a cubic curve and the like. However, if the curve is also divided into very short sections, it will approach a straight line as much as possible. If a part of the curve is close to a straight line, the point of interest of the present invention is to use a point that can be replaced by a simple average instead of a complicated approximation calculation. FIG. 1 shows a system diagram of an embodiment of the present invention. In the memory circuit 5, the temperature compensation information of the VCXO 13 is detected in advance by 9 bits and halved (to halve in binary means deleting the least significant 1 bit) 8b
It is stored as it. [0007] The temperature information of the temperature sensor 1 is converted into a 9-bit digital signal by an A / D conversion circuit 2 and supplied to a compensation information reading circuit 3. In the compensation information reading circuit 3, 9 bits
Are supplied to the memory circuit 5 via the address adding circuit 4 and are used as an address for reading out the compensation information stored in the memory circuit 5, and the least significant 1 bit is
A D / A circuit by switching the output of the address adder 4 and the output of the adder 9 from the output of the first switch circuit 6 and the doubling circuit 10 which distributes the output of the memory circuit 5 to the first latch circuit 7 and the second latch circuit 8 Second switch circuit 1 to be supplied to 12
1 is used for control. The distribution of the compensation information of the memory to the first latch circuit 7 and the second latch circuit 8 is performed with the lowest 1 bit of 9 bits of the temperature information of the temperature sensor 1. When this 1 bit is 0, the output of the memory circuit 5 is supplied to the first latch circuit 7 and passes through the doubling circuit 10 (in the doubling circuit, the compensation information of 8 bits from the memory has the contents 0 at the lowest order). Add 1 bit to 9 bits) 2nd
The signal reaches the D / A conversion circuit 12 via the switch circuit 11. In addition, in the address adding circuit 4, when the least significant 1 bit of the 9-bit temperature information of the temperature sensor 1 is 1, the upper 8b
The information of the address obtained by adding 1 to the binary signal of "it" is output from the memory circuit 5 and supplied to the second latch circuit 8 (1
The compensation information of the next higher address is read out), the data of the first latch circuit 7 and the data of the second latch circuit 8 are added by the addition circuit 9 and the D / A conversion circuit 12 is passed through the second switch circuit 11.
Leads to. The first switch circuit 6 connects the doubling circuit 10 to the D / A circuit 12 when the least significant one bit of the 9 bits of the temperature information of the temperature sensor 1 is 0, and outputs the temperature information of the temperature sensor 1. When the least significant 1 bit of 9 bits is 1, the circuit operates so as to connect the adder circuit 9 and the D / A circuit 12. Second
The switch circuit 11 is configured to transmit 9 bi of temperature information of the temperature sensor 1.
When the least significant bit of t is 0, the doubling circuit 10 and D /
A circuit 12 is connected, and 9 bi of temperature information of temperature sensor 1 is
When the least significant 1 bit of t is 1, the addition circuit 9 and the D / A
It operates to connect the circuit 12. In addition to the above-described method, a VCXO
The temperature compensation information of 13 is stored in 8 bits and the doubling circuit 10 is stored.
And replace the adder circuit 9 and the second switch circuit 1
Although it is conceivable to insert a 回路 circuit between the 1 and １1, the result is that even if the addition circuit 9 obtains 9-bit compensation information and reduces the compensation information to ８8-bit compensation information by the 十分 circuit, it is not sufficiently practical. It is in the range that does not interfere. According to the present invention, the compensation information is stored by 1 bi-level as compared with the prior art without changing the capacity of the memory circuit 5 as described above.
t can be obtained, and the number of compensation information can be twice as large as that of the conventional technology. Also, if compensation is performed to the same extent as in the prior art, the capacity of the memory circuit 5 is 7 bits.
X128, which is about half. Moreover, the circuits added for the present invention are simple and inexpensive. In the embodiment, an example is described, and the present invention can be applied to a device having a different number of bits or addresses. According to the present invention, the fineness of the frequency control with respect to the temperature change of the digital temperature compensated piezoelectric oscillator is increased by 1/2 at the interval of the control temperature and by 1 bit at the fineness of the frequency compensation information. Therefore, a digital temperature compensated piezoelectric oscillator having a smaller frequency deviation can be obtained. In the case where the fineness is the same as that of the prior art, the capacity of the memory circuit is sufficient, so that miniaturization and cost reduction can be realized.

[Brief description of the drawings] FIG. 1 shows a system diagram of an embodiment of the present invention. FIG. 2 shows a system diagram of the prior art. [Explanation of symbols] 1 Temperature sensor 2 Analog / digital conversion circuit 3 Compensation information readout circuit 4 Address addition circuit 5 Memory circuit 6 First switch circuit 7 First latch circuit 8 Second latch circuit 9 Addition circuit 10 double circuit 11 Second switch circuit 12 Digital / analog conversion circuit 13 VCO

Claims (1)

(57) [Claim 1] A temperature sensor, an analog / digital conversion circuit for inputting and analog-to-digital converting an analog temperature signal output from the temperature sensor, and an analog / digital conversion circuit A memory circuit to which the output digital temperature signal is supplied as an address, and a D / A receiving a compensation information signal corresponding to the digital temperature signal output from the memory circuit;
A digital / analog conversion circuit for converting,
And a VCXO controlled and supplied with an analog compensation information signal output from an analog conversion circuit. A digital temperature compensated piezoelectric oscillator comprising: a memory corresponding to an output of the temperature sensor between an input and an output of the memory circuit; A compensation information reading circuit for reading a digital compensation information signal from the circuit; a memory circuit side output of the compensation information reading circuit to an input of the memory circuit; and an output of the memory circuit to the memory circuit of the compensation information reading circuit. An address addition circuit is connected between the side inputs, a signal from the compensation information reading circuit is input, and the connected first latch circuit or the second latch circuit is connected to the temperature sensor.
Due to the difference of the least significant 1-bit signal of the output signal,
A first switch circuit for switching the output destination of the temperature sensor is connected, and the least significant 1-bit signal of the output signal of the temperature sensor is 0.
Output of the first latch circuit to which the compensation information signal is input
Is connected to a double circuit , and the least significant 1-bit signal of the output signal of the temperature sensor is 1
Output of the second latch circuit to which the compensation information signal is input
The signal and the output signal of the first latch circuit are connected to each other.
And an output signal from the adder circuit and an output signal from the doubling circuit.
Is the least significant one bit of the output signal of the temperature sensor.
A second switch circuit that switches in conjunction with the first switch circuit due to a difference between the first and second switch circuits, and an output signal of the second switch circuit is input to the digital / analog conversion circuit. A digital temperature compensated piezoelectric oscillator characterized by the following: