JPH0766038B2 - Integrated circuit device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an analog / digital mixed integrated circuit device, and more particularly to a device for facilitating an operation test of an analog circuit portion thereof.

[Conventional technology]

In an integrated circuit device with a mixture of analog and digital, especially if the output of the digital circuit part is not directly output to the external terminal but is directly connected to the analog circuit part and is output to the analog circuit part, the test is performed to check the operation of the analog circuit part. It has been conventionally practiced to separately provide a terminal.

FIG. 2 is a conventional example thereof, in which 10 is a digital circuit section, 20 is an analog circuit section, 1 is an analog input terminal, 2 is a test state selection terminal, A and B are switches, and 5 is an inverter. .

The analog circuit section 20 includes an operational amplifier 21, resistors 22 and 23,
It is composed of capacitors 24 and 25 and an analog section output terminal 4.

The switches A and B are MOSFETs A1, A2 and B1, B2, respectively.
It consists of

The operation mode (operation state) of the conventional device is controlled according to the high and low level control signals applied to the operation mode control terminal (not shown).

The circuit of FIG. 2 is intended to output the digital output of the CMOS circuit to the outside through the active filter which is the analog circuit section 20.

The switches A and B are controlled by the terminal 2. When the terminal 2 is L ₀ , the switch A is ON and B is OFF, and when the terminal 2 is Hi, the switch A is OFF and B is ON. The analog circuit section has an operational amplifier 21, which operates as an active filter.

During normal use, the terminal 2 is set to L _{0 and} the output of the digital circuit section 10 is guided to the analog circuit section 20. In the test state, the terminal 2 is set to Hi and the output of the digital circuit section 10 is cut off. Instead, the input from the terminal 1 is guided to the analog circuit section 20. At this time, a test signal voltage is input from the terminal 1 at the same time. For example, a DC voltage is applied as the signal voltage to test the offset voltage of the output, or a sine wave is applied to the gain or frequency characteristic (so-called f characteristic). ), Output impedance etc. can be easily checked.

[Problems to be solved by the invention]

By the way, in the case of an analog-digital mixed integrated circuit device in which these tests must be performed in a normal state, the type of test is limited because the input is in a pulse state, and the frequency, duty, etc. can be easily changed. If it is not, the test becomes very difficult, but in the conventional integrated circuit device, a signal can be directly input to the analog circuit unit from the outside as described above, so that the test of the analog circuit unit can be easily performed.

However, this conventional integrated circuit device has a drawback that it requires two terminals for testing the analog circuit portion, which causes an increase in the number of terminals of the integrated circuit.

The present invention has been made to solve the above-mentioned problems of the conventional ones, and an integrated circuit device capable of performing an operation test of an analog circuit section without providing a terminal dedicated thereto is provided. Has an aim.

[Means for solving problems]

An integrated circuit device according to the present invention is formed by mixing an analog circuit portion and a digital circuit portion on the same semiconductor substrate,
In an integrated circuit device in which the output of the digital circuit unit is connected to the analog circuit unit inside the device, and the operating state of the digital circuit unit is controlled according to a high level or low level control signal, the high level or A control terminal to which a low-level control signal or an intermediate level control signal is applied, and when the high-level or low-level control signal is applied to the control terminal, the control signal is sent to the digital circuit section. When the control signal of the intermediate level is applied, the device is set to the test mode of the analog circuit section, and the control signal of the intermediate level is replaced with the output signal of the digital circuit section for testing the analog circuit section. It is provided with an analog section test circuit which is given as a signal.

[Action]

According to the present invention, with the above-described configuration, when a signal at an intermediate level between the high level and the low level is applied to the control terminal, the analog circuit section enters the test mode,
Since the intermediate level control signal is applied to the analog circuit section as a test signal, the operation mode control terminal can be used not only as a test state selection terminal but also as a test analog signal input terminal.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 3 shows an integrated circuit device according to an embodiment of the present invention.
The figure shows a concrete circuit configuration example when this is realized by a CMOS integrated circuit with a power supply voltage of 5V.

In FIG. 1, the same reference numerals as those in FIG. 2 indicate the same elements, and 30 is a test mode determination circuit, which is used when a high-level or low-level control signal is applied to the control terminal 3 together with the switch A and the switch B. Transmits the control signal to the digital circuit section 10 as its control signal, and when a control signal of an intermediate level between high level and low level is applied, the device is set to the test mode of the analog circuit section 20 and the control signal of the intermediate level is set. In place of the output signal of the digital circuit section 10, an analog section test circuit is provided to the analog circuit section 20 as a test signal. Reference numeral 3 is a control terminal. The control terminal 3 is for normally selecting the operating state of the digital section by the input voltage of Hi or L ₀ , and is normally fixed at the voltage of Hi or L ₀ for use. It can exist without being limited to.

However, in the present invention, this control terminal is given another role so that it can be used as a test state control terminal and an analog input terminal in addition to the digital operation mode control terminal. That is, the control terminal is normally Hi or L ₀ , and this input is guided to the test mode determination circuit 30. Here, when the voltage is Hi or L ₀ , it is determined to be in the normal operation state, the operation control information of the digital circuit unit 10 is sent to the line b, and the switch A is turned on to the line c and the switch B is turned on. Information that turns off is sent. As a result, the operating state of the digital circuit section is normally selected, and the output of the digital circuit section is normally transmitted to the analog circuit section.

On the other hand, in the test state, the control terminal has a DC voltage between HI and L _0.
Voltage is applied and AC voltage can also be superimposed. That is, in the test mode determination circuit, the input from line a
However, it is not L _{0 and} is recognized as the third information, and is determined to be the test state. As a result, switch A is installed on line c.
Information is sent to turn OFF and switch B ON, which disconnects the signal from the digital circuit section to the analog circuit section. As a result, some information appears on line b, but that information has no meaning. Since the signal from the line a is transmitted to the analog circuit section, the control terminal 3 has Hi
Alternatively, an analog test input signal can be applied in the voltage range where it is not detected as Lo.

Most of the analog circuit tests are DC, which is about 1/2 of the power supply voltage.
This input voltage range cannot be a hindrance to the test as it can be checked at the voltage input.

FIG. 3 is a concrete circuit example of the circuit shown in FIG. 1 applied to a CMOS integrated circuit with a single 5 V power supply. In the figure, 31 and 32 are voltage comparators, 33 is an AND gate, and 34 is an inverter. is there.

The reference voltage of + 4V is applied to the non-inverting input terminal of the voltage comparator 31.
A reference voltage of +1 V is applied to the inverting input terminals of the voltage comparator 32, respectively. Therefore, if the input voltage of the control terminal is 1V or less, it corresponds to Lo input, and if it is 4V or more, it corresponds to Hi input. When the Hi or Lo input is applied, the operation of the digital circuit section is accurately selected by the line b, and the switch A is turned on.
N and the switch B are turned off, and the output of the digital circuit section is accurately input to the analog circuit section. On the other hand, when the control terminal input is between 1V and 4V, switch A is OFF and switch B is ON.
And the voltage on line a is guided to the analog circuit section.
At this time, the voltage of the line b becomes Hi, but the output signal of the digital circuit section is not guided to the analog circuit section.

From the above, for example, if a sine wave input with an instantaneous DC voltage swing of 1V to 4V is input to the control terminal, the test state is entered and the signal can be input to the analog circuit section. I can.

As described above, according to this embodiment, the analog circuit section can be tested without increasing the number of terminals.

In the above embodiment, only the output of the digital circuit unit is directly connected to the analog circuit unit inside the integrated circuit device, but the present invention is applicable to all analog and digital mixed devices as long as it has an operation mode control terminal. Can be applied to
The same effect as that of the above embodiment is obtained.

Further, by arranging the switch A and the switch B also in the connecting portion between the other digital circuit section and the analog circuit section, one test mode determination circuit can test arbitrary plural analog circuits. Yes, and only one input terminal is required for the test.

〔The invention's effect〕

As described above, according to the integrated circuit device of the present invention, the analog circuit part and the digital circuit part are formed in a mixed manner on the same semiconductor substrate, and the output of the digital circuit part is the analog circuit part inside the device. In an integrated circuit device connected to, the operating state of the digital circuit section is controlled according to a high-level or low-level control signal,
A control terminal to which the high-level or low-level control signal or a control signal at an intermediate level thereof is applied, and when the high-level or low-level control signal is applied to the control terminal, the control signal is applied to the digital circuit unit. To the analog circuit instead of the output signal of the digital circuit section by setting the device as a test mode of the analog circuit section when the control signal of the intermediate level is applied to the analog circuit. Since the analog section test circuit provided as a test signal is provided in the section, the operation test of the analog circuit section can be easily performed without providing a separate terminal.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an integrated circuit device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a conventional integrated circuit device, and FIG.
The figure is a diagram showing a specific circuit configuration of FIG. In the figure, 10 is a digital circuit section, 20 is an analog circuit section, 30 is a test mode determination circuit (analog section test circuit), A and B are switches, and 3 is an operation mode control terminal.

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Claims (1)

[Claims] 1. An analog circuit section and a digital circuit section are formed in a mixed manner on the same semiconductor substrate, and the output of the digital circuit section is connected to the analog circuit section inside the device, and at the high level or low level. In an integrated circuit device in which the operation state of the digital circuit unit is controlled according to a control signal, a control terminal to which the high-level or low-level control signal or a control signal at an intermediate level thereof is applied, and the control terminal When a high-level or low-level control signal is applied, the control signal is transmitted to the digital circuit section as its control signal, and when the intermediate-level control signal is applied, the apparatus is operated in the test mode of the analog circuit section. As a substitute for the output signal of the digital circuit section for the intermediate level control signal, the analog circuit section is supplied with a test signal. Integrated circuit device characterized by comprising an analog part test circuit for providing a.