JPS5951609A - Integrated circuit device - Google Patents

Abstract

PURPOSE:To select the oscillating frequency, by changing the time constant of an oscillating circuit built in an integrated circuit device with external control. CONSTITUTION:When a high level is impressed from an external terminal E, an analog switch 80 is turned on and a switch 81 is turned off. Then, the charge passes through the switch 80 and stored or discharged in/form a capacitor via a resistor 60. In impressing a low level to an external terminal E, the switch 80 is turned off and the switch 81 is turned on. The charge passes through resistors 61, 60 and is stored in capacitors 70, 71. The time required when the charge is removed from an output D to an input C is more than the case with the external terminal E impressed with the high level by the resistor 61 increased. Further, the timewise change in the potential at the input C is less in the potential change by the increased capacitance even if the same amount of the charge flows to the input C, because the capacitor 71 is increased in comparison with the former. Thus, the time in the capacitance change is increased and the oscillating frequency is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an integrated circuit device, and more particularly to an oscillation circuit built into an integrated circuit including a resistor and a capacitor.

Conventionally, the oscillation frequency of an oscillation circuit built into an integrated circuit device has already been determined by built-in resistors and capacitors at the time of product design, and it has been difficult for the user to change this oscillation frequency.

FIG. 1 is a circuit diagram showing an oscillation circuit within such a conventional integrated circuit device. In FIG. 1, the Schmitt circuit 1 is constructed by adding a capacitor 20 between input A and ground and a resistor 10 between input A and output B.
oscillate.

When input A is at high level, the potential at output B is at low level, and charge is stored in capacitor 20. Due to the potential difference between input A and output B, the charge passes through resistor 10 and escapes to output B. As a result, the potential of the human power A decreases, and when it reaches a certain potential ■1, the Schmitt circuit 1
is regarded as a low level input, and the output B becomes a no-y level. Therefore, the charge passes through the resistor 10 from the output B and is stored in the capacitor 20. Then, the potential of the human power A starts at υ and then reaches the potential ■2, and the output B is inverted to low level. Oscillation is performed by repeatedly changing the potential of input A between potentials vl and v2, and the oscillation frequency is as follows:
It is determined by the time from l to ■2 and from the potential ■2 to v1, that is, the charge transfer time, and this is determined by the resistance value 10
This is determined by the size of the capacitance of the capacitor 20.

The oscillation frequency in the conventional example described above is fixed by the resistor 10 and the capacitor 20. To change this, input Ai is pulled out as a terminal externally, and a capacitor is added here to change the capacitance. You can change the frequency by increasing the input A1 and output B, or by connecting a resistor between them and lowering the resistance value by connecting both input A1 and output B to external terminals. It has the disadvantage that it becomes larger and requires external elements to be added and replaced to change the frequency.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above drawbacks and provide an integrated circuit device having an oscillation circuit whose oscillation frequency can be selected by a signal from an external circuit of the integrated circuit device.

The present invention relates to an integrated circuit device having a built-in oscillation circuit including a resistor and a capacitor, which includes a function of changing the oscillation frequency by a signal from an external circuit of the integrated circuit device. be.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a circuit diagram of one embodiment of the present invention. This integrated circuit device includes a Schmitt circuit 50 and analog switches so and si, which are turned on (OFF) when the gate signal is at a low level and turned on (ON) when the gate signal is at a high level. First, we will discuss the case where the Gino-I level is applied to the external terminal E. At this time, the analog switch 80 is on and the analog switch 81 is off. Therefore, the charge passes through the analog switch 80,
It passes through the resistor 60 and is stored in the capacitor 70 or released. Next, when a low level is applied to the external terminal E, the analog switch 80 is turned off and the analog switch 81 is turned on.

At this time, the charge passes through the resistor 61.60 and the capacitor 7
It is stored in 0.71. The time required for the charge to move from the output to the input C is longer than that required when a noise level is applied to the external terminal E due to the increase in the resistance 61. Furthermore, since the number of capacitors 71 has been increased compared to the former case, the change in the potential of the input C over time is smaller than that of the former, so even if the same amount of charge flows into the input C, the potential change is smaller due to the increased capacitance.

As a result of the above, input C changes from potential V1 to ■2 and from potential ■2 to ■
It takes more time to change to 1 than the former. Therefore, the oscillation frequency becomes low.

In this way, in this embodiment, the oscillation frequency can be selected by changing the time constant of the oscillation circuit built into the integrated circuit device using a control signal from outside the integrated circuit device. Alternatively, it is possible to make only the capacitor variable, or to select multiple oscillation frequencies by using multiple resistors, capacitors, analog switches, and external terminals.

As explained above, according to the present invention, a tremendous effect can be obtained in that the user can select the oscillation frequency according to the application.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of an oscillation circuit section of a conventional integrated circuit device, and FIG. 2 is a circuit diagram showing an integrated circuit device according to an embodiment of the present invention. 1.50...Schmitt circuit, 10,60.6
1... Resistance, 20, 70, 71... Condenser/su, 80.81... Analog switch, 54.
・・・・・・A/No. A, C：Input, B, D：Output, E：External terminal.

Claims (1)

[Claims] An oscillation circuit including a resistor and a capacitor is built-in. An integrated circuit device that is patented in that the integrated circuit device is configured such that the oscillation frequency of the oscillation circuit is selected by a control signal input from the outside.