JP2527832Y2 - Programmable oscillation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a programmable oscillator circuit capable of setting the frequency of an output signal using a digital signal.

[Prior Art] Conventionally, an oscillator that outputs a signal of a predetermined frequency is used in various electric circuits. In particular, since an oscillator is also required to generate a clock signal as a basic signal in an IC, an LSI, or the like, an oscillator is required not only in an analog circuit but also in a digital circuit, and this importance is very large.

Among such oscillators, there is a programmable oscillator that can set an oscillation frequency according to a digital signal. According to this programmable oscillator, a predetermined frequency can be oscillated in accordance with an input signal, so that the versatility is high and the programmable oscillator is used in various circuits. Among these programmable oscillators, there is a programmable CR oscillator.

This has a plurality of capacitors and resistors inside, and oscillates at a predetermined frequency by switching between them. Since a wide range of oscillation can be performed by a simple circuit, it is widely used in programmable oscillators.

As shown in FIG. 2, for example, the programmable CR oscillator 30 receives a digital signal for specifying an oscillation frequency and outputs a signal of the specified frequency. For example, when the input digital data is 8-bit signal may identify the value of 2 ⁸ That 156,
Usually, a frequency in the range of 20 Hz to 100 kHz can be specified by three significant figures. When such a digital signal is input, the programmable CR oscillator 30
Can output a signal of a predetermined frequency by switching an internal capacitor and resistance.

[Problem to be Solved by the Invention] The conventional programmable oscillation circuit has the above-described configuration, and the oscillation frequency is determined by the oscillation circuit corresponding to the initially set digital signal. Therefore, the accuracy of the frequency in the output signal of the programmable oscillator is determined by the internal resistor C and capacitor R. Therefore, unless very accurate capacitors C and resistors R are used,
There has been a problem that it is not possible to obtain a highly accurate oscillation frequency according to a digital signal.

An object of the present invention is to provide a programmable oscillation circuit that can obtain a highly accurate oscillation frequency even when the multiplier accuracy of the internal capacitor C and the resistor R is not very high.

Means for Solving the Problems In order to achieve the above object, the present invention provides a correction ROM for receiving digital data on an oscillation frequency and outputting correction digital data stored in advance at an address corresponding to the digital data. And a programmable oscillator that outputs a signal of a frequency corresponding to the correction digital data output from the correction ROM, and corrects the frequency of the output signal in the programmable oscillator to output a signal of an accurate frequency. Features.

[Operation] The programmable oscillation circuit according to the present invention has the above-described configuration, and includes a correction ROM storing a correction value. Therefore, by changing the value stored in the correction ROM, the data actually input to the programmable CR oscillator can be changed. Therefore, by rewriting the data in the correction ROM according to the actual output of the programmable oscillation circuit, the variation in the capacitor C and the resistance R in the programmable CR oscillator can be corrected by the correction ROM, and the signal of the accurate frequency can be corrected. Can be obtained.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of a programmable oscillation circuit according to the present invention. The programmable oscillation circuit 100 has a correction ROM 10 for storing a predetermined correction value, a predetermined number of capacitors C, and a resistor R. The programmable CR oscillator 20 performs predetermined switching based on input data and oscillates and outputs a signal of a predetermined frequency based on the predetermined switching.

The programmable CR oscillator 20 outputs a signal of a frequency specified according to the input digital data, and performs switching of a capacitor C and a resistor R which are set in advance according to the input data. And, in order to output in this switched CR circuit,
The frequency of the output signal varies depending on the values of the internal capacitor C and the resistor R.

Here, in the present invention, various digital data are input to the programmable CR oscillator, and the output is measured. Then, if such identification is performed, an error in the programmable CR oscillator 20 can be detected. Then, this error is eliminated by the correction ROM 10. That is, in the present invention, the data input to the programmable CR oscillator 20 is corrected instead of adjusting the internal circuit of the programmable CR oscillator 20 to make the oscillation frequency desired. That is, by comparing the frequency of the digital input and the output as described above,
If the characteristics of the oscillator are known, the value of the input corresponding to the output can be determined by reversing the relationship. Therefore, in the present invention, the input data corresponding to the output signal thus obtained is written in the correction ROM 10.

That is, the value of the input data corresponding to the output signal desired at that time is written to the address corresponding to the input data in the above-mentioned measurement performed in advance. By doing so, if digital data specifying a signal of the same desired frequency as in the prior art is input, this is the input data of the programmable CR oscillator for obtaining the output of the frequency to which the input digital data should correspond. And a desired output is obtained.

Thus, according to the present invention, the input portion of the digital data is provided with the correction ROM 10 for correcting the input data,
As a result, the error of the programmable CR oscillator 20 can be compensated, so that even if the accuracy of the capacitor C and the resistor R inside the programmable CR oscillator 20 is bad, the error can be ignored and an accurate output can be obtained. it can.

The configuration of the programmable CR oscillator itself does not need to be changed at all, and the input digital data itself may be exactly the same as the conventional one.
Further, since the correction ROM 10 is set once and does not need to be changed thereafter, a nonvolatile memory, for example, an EP ROM is preferable.

[Effects of the Invention] As described above, according to the programmable oscillation circuit of the invention, it is not necessary to employ a high-precision capacitor C and resistor R inside the programmable CR oscillator. Can be facilitated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a programmable oscillation circuit according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a conventional programmable oscillation circuit. 10: Correction ROM 20: Programmable CR oscillator 100: Programmable oscillation circuit

Claims (1)

(57) [Scope of request for utility model registration] 1. A correction ROM for inputting digital data about an oscillation frequency and outputting correction digital data stored in advance at a corresponding address, a frequency corresponding to the correction digital data output from the correction ROM. 1. A programmable oscillator circuit, comprising: a programmable oscillator that outputs a signal of the programmable oscillator; and correcting a frequency of an output signal in the programmable oscillator and outputting a signal of an accurate frequency.