JPH05343622A - Semiconductor integrated circuit having self-diagnostic circuit - Google Patents

Abstract

PURPOSE:To accurately detect whether test function is started when an abnormal leak current different from a normal current flows, in the case of judgment of the test function of a semiconductor integrated circuit. CONSTITUTION:A resistor R1 is connected with a signal line 2 connecting an input terminal A with an inverter 1. An N-channel type MOS transistor Q1 is connected in series with the resistor R1. The output terminal of a test function switching circuit 11 is connected with an internal circuit 10 and the gate of the transistor Q1. When a test function control signal 3 as the output of the test function switching circuit 11 is activated, the transistor Q1 is in the state of electric continuity. By measuring a current flowing through the transistor Q1, the test function of a semiconductor integrated circuit is judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit having a self-diagnosis circuit, and more particularly to a semiconductor integrated circuit having a test function detecting circuit.

[0002]

2. Description of the Related Art As a semiconductor integrated circuit having a conventional self-diagnosis circuit, as shown in FIG.
There is a circuit configured by connecting a P-type MOS transistor Q6 having a gate input thereof as a gate input and an N-type MOS transistor Q7 having a gate input of a test function control signal T1 in series between a power supply and a ground.

To detect a test function in a circuit as shown in FIG. 3, the test function detection circuit is activated or deactivated,
In these two states, the power supply current of the entire semiconductor integrated circuit is measured, and these are compared to make a determination. Next, this specific method will be described.

In FIG. 3, when the test function is activated by the test function switching circuit 22, the test function control signal T1 goes high. At this time, the DC signal I1 determined by the channel width of the transistors Q6 and Q7 flows between the power supply and the ground by setting the clock signal CL1 to low. In this state, the direct current I2 (not shown) flowing between the power supply and the ground of the entire semiconductor integrated circuit is measured. When the test function is deactivated by the test function switching circuit 22, the test function control signal T1 goes low and the transistor Q7 is turned off. Therefore, the transistors Q6 and Q7 are turned on.
No current flows through. In this state, a DC current I3 (not shown) flowing between the power supply and the ground of the entire semiconductor integrated circuit is further measured. If I1 ≦ (I2-I3), it can be detected that the test function is activated, and I1>
If it is (I2-I3), it can be detected that the test function is not activated.

[0005]

However, in the semiconductor integrated circuit having the above-mentioned conventional self-diagnosis circuit, the DC currents when the detection circuit is selected and when the detection circuit is not selected are measured, and these values are compared and judged. It is necessary to set the value of the DC current flowing through the verification circuit so that the value of the DC current at the time of selection can be sufficiently judged by the ammeter as compared with the value of the DC current at the time of selection.

In particular, depending on the semiconductor integrated circuit in the early stage of development, there is a high possibility that leakage current other than circuit operation will flow due to insufficient etching due to instability of the diffusion process and dust. Therefore, if the current value of the verification circuit is set with respect to the DC current value due to normal circuit operation, there is a problem that correct determination cannot be performed when the leak current is large.

For example, in a semiconductor integrated circuit in which a current of 1 μA flows normally when the verification circuit is not selected, if the transistor size is set so that about 10 μA flows in the verification circuit, about 11 μA will be selected when the verification circuit is selected. It is possible to correctly determine that the test function has been set by the current flowing in. However, if the leakage current other than the circuit current due to normal operation exceeds 1 mA, it will be about 1.0 when the verification circuit is selected.
There is a problem in that a current of 1 mA flows and correct determination cannot be performed if a measurement error or the like is taken into consideration.

The present invention has been made in view of the above problems, and even if an abnormal leak current other than the normal current flows, it is possible to accurately detect whether or not the test function has been entered. It is an object to provide a semiconductor integrated circuit having a circuit.

[0009]

A semiconductor integrated circuit having a self-diagnosis circuit according to a first invention of the present application is a semiconductor integrated circuit having a self-diagnosis circuit, and a signal line connecting an input or an input pad to the input circuit, A resistance element and M which are provided between the signal line and the power supply or the ground and are connected in series
An OS transistor is provided, and the MOS transistor becomes conductive when a test function control signal applied to the gate of the MOS transistor is activated.

A semiconductor integrated circuit having a self-diagnosis circuit according to a second aspect of the present invention is a semiconductor integrated circuit having a self-diagnosis circuit, wherein a signal line connecting an input or an input pad and an input circuit, and the signal line and ground are provided. A first resistance element and a first MOS transistor which are provided between and connected in series, and a second resistance element and a second MOS which are provided between the signal line and the power supply and connected in series A first MOS transistor having a transistor, and the first MOS transistor is turned on when a first test function control signal applied to the gate of the first MOS transistor is activated.
A second voltage applied to the gate of the second MOS transistor
When the test function control signal of the
Is characterized in that the MOS transistor is turned on.

In the first and second inventions of the present application, the MOS which is rendered conductive by the test function control signal.
It is preferable to determine the test function of the semiconductor integrated circuit by measuring the current flowing through the transistor.

[0012]

In the semiconductor integrated circuit having the self-diagnosis circuit according to the present invention, a signal line connecting the input terminal and the input circuit,
It has a resistance element and a MOS transistor which are provided between the power supply and the ground and are connected in series, and the MOS transistor is in a conductive state when a test function control signal applied to the gate of the MOS transistor is activated. become. Then, the test function of the semiconductor integrated circuit is determined by measuring the current flowing through the MOS transistor that is rendered conductive by the test function control signal. As a result, the semiconductor integrated circuit having the self-diagnosis circuit according to the present invention accurately detects whether or not the test function has been entered, even when the power supply current is increased by an abnormal leak current other than the normal current. be able to.

[0013]

Embodiments of the present invention will now be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a semiconductor integrated circuit having a self-diagnosis circuit according to the first embodiment of the present invention. The input terminal A is connected to the internal circuit 10 via the inverter 1 which is a first stage circuit. The signal line 2 connecting the input terminal A and the input terminal of the inverter 1 is connected to the N-channel type M
A BVDS type input protection circuit including an OS transistor Q2 is connected. A resistor R1 is connected to the signal line 2 between the BVDS type input protection circuit and the inverter 1, and an N channel type MOS transistor Q1 is connected in series to the resistor R1. Furthermore, the internal circuit 10
The output terminal of the test function switching circuit 11 is connected to the gate of the transistor Q1.

Next, the operation of the semiconductor integrated circuit having the self-diagnosis circuit according to the first embodiment constructed as described above will be described. When the test function switching circuit 11 activates the test function, the test function control signal 3 becomes high and the transistor Q1 is turned on. When the test function is inactivated by the test function switching circuit 11, the test function control signal 3 becomes low and the transistor Q1 is turned off.

On-resistance RQ1 and resistance R of transistor Q1
When the value (RQ1 + R1) obtained by combining 1 and 5 is set to, for example, 5 MΩ, and 5 V is applied to the input signal terminal A when the test function control signal 3 is high, the resistance R from the input signal terminal A is set.
A current of 1 μA flows to the ground via 1 and the transistor Q1. This current is measured by the ammeter of the input signal driver in the measuring device. Thus, considering the variation in the resistance value, it is determined that the test function is operating normally if a current value of 0.5 μA to 2 μA is measured, and if the value is other than the above value, the test function is normal. It is determined that it is not operating.

Next, a second embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a block diagram showing a semiconductor integrated circuit having a self-diagnosis circuit according to the second embodiment of the present invention. The second embodiment is a semiconductor integrated circuit having a plurality of test functions that are not activated at the same time.
This is an example in which one test signal can be judged by using one input signal terminal A.

When the test function control signal 6 which is the output of the test function switching circuit 11b is high, a test is performed by measuring the current flowing from the input signal terminal A to the ground through the resistor R2 and the N-channel type MOS transistor Q3. Determine the function. At this time, the test function control signal 7 that is the output of the test function switching circuit 11a is low, and the output of the inverter 8 that receives the test function control signal 7 is applied to the gate of the P-channel MOS transistor Q4. Therefore, the transistor Q4 is off.

On the other hand, when the test function switching circuit 11a is set and the test function control signal 7 becomes high, the transistor Q4 is turned on. Then, since the test function control signal 6 becomes low, the transistor Q3 is turned off. At this time, if the input signal terminal A is 0V, a current determined by a value (R3 + RQ4) obtained by combining the resistor R3 and the on-resistance RQ4 of the transistor Q4 is supplied to the input signal terminal A through the transistor Q4 and the resistor R3. Flowing.

That is, when the test function control signal 7 becomes high, a current having a polarity opposite to that of the current flowing through the transistor Q3 is measured, and the test function switching circuit 11a.
And whether or not 11b is activated with one input terminal,
It can be clearly determined.

[0022]

As described above, according to the semiconductor integrated circuit having the self-diagnosis circuit of the present invention, in order to detect the test function, the input terminal is provided via the MOS transistor for inputting the test function control signal to the gate. Since the value of the current that flows from the ground to the power supply is measured, it is possible to detect whether the test function has been entered even if an abnormal leakage current other than the normal current flows as the power supply current, which is often the case in the early stages of development. Can be done accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing a semiconductor integrated circuit having a self-diagnosis circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a semiconductor integrated circuit having a self-diagnosis circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a semiconductor integrated circuit having a conventional self-diagnosis circuit.

[Explanation of symbols]

 1; Inverter 10; Internal circuit 11; Test function switching circuit Q1, Q2; N-channel type MOS transistor

Claims (3)

[Claims] 1. In a semiconductor integrated circuit having a self-diagnosis circuit, a signal line connecting an input or an input pad and an input circuit, and a resistance element provided between the signal line and a power supply or ground and connected in series, and A semiconductor integrated circuit having a MOS transistor, wherein the MOS transistor is rendered conductive when a test function control signal applied to the gate of the MOS transistor is activated. 2. In a semiconductor integrated circuit having a self-diagnosis circuit, a signal line connecting an input or an input pad and an input circuit, and a first resistance element provided between the signal line and ground and connected in series. And a first MOS transistor, and a second resistance element and a second MOS transistor that are provided between the signal line and the power supply and connected in series, and have a gate connected to the first MOS transistor. When the first test function control signal to be applied is activated, the first MOS transistor becomes conductive and the second test function control signal to be applied to the gate of the second MOS transistor is activated. When the second MO
A semiconductor integrated circuit having a self-diagnosis circuit characterized in that an S transistor is in a conductive state. 3. The self-test according to claim 1, wherein the test function of the semiconductor integrated circuit is determined by measuring a current flowing through a MOS transistor which is rendered conductive by a test function control signal. A semiconductor integrated circuit having a diagnostic circuit.