JP2001343435A - Method and apparatus for inspecting electronic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method, capable of performing an input level test by one function test and capable of inspecting an electronic circuit, without being affected by hysteresis characteristics. SOLUTION: There are provided a process for measuring the change in the timing of an output level at an output terminal, while inputting a test signal having a lamp waveform to the input terminal of the electronic circuit and a process for calculating an input level for normally operating the electronic circuit, on the basis of the level of the test signal corresponding to this timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for testing an electronic circuit, and more particularly, to a method for testing an input level for operating an electronic circuit normally. Further, the present invention relates to an inspection apparatus using such an inspection method.

[0002]

2. Description of the Related Art Generally, an electronic circuit such as a semiconductor integrated circuit including a logic circuit and a memory has an I / O (input / output) cell for inputting / outputting a signal. In order to perform an input level test of such an electronic circuit, a function test is repeatedly performed while changing a high level or a low level of a test signal (rectangular wave) input to an input cell. For example, when changing the high level of the test signal from 0.9 V to 2.4 V at 0.1 V intervals, it was necessary to perform 16 function tests. Function test result is PASS / FA
Since it is indicated by IL, by repeating the function test while changing the level of the test signal, it is possible to inspect in which range the input level normally operates.

[0003]

However, according to the above-described inspection method, there is a drawback that a long time is required for the inspection since the function test needs to be executed many times. Also, in the case of an electronic circuit having a hysteresis characteristic such as a Schmitt trigger circuit, it is difficult to accurately inspect an input level for normal operation because the electronic circuit is affected by the previous history.

In view of the above, the present invention provides a method and an apparatus capable of performing an input level test with one function test and inspecting an electronic circuit without being affected by hysteresis characteristics. The purpose is to do.

[0005]

In order to solve the above-mentioned problems, a method for testing an electronic circuit according to the present invention is to provide a method for testing an electronic circuit while inputting a test signal having a ramp waveform to at least one input terminal of the electronic circuit. (A) measuring a timing at which an output level changes at at least one output terminal corresponding to at least one input terminal of the above, and a test signal level corresponding to the timing measured in the step (a). (B) determining an input level for the electronic circuit to operate normally.

The electronic circuit inspection apparatus according to the present invention includes an integrating circuit for generating a test signal having a ramp waveform by integrating an input rectangular wave signal, and the test circuit is connected to at least one input terminal of the electronic circuit. A test signal supply unit for inputting a test signal and a switching unit for switching a time constant of the integration circuit are provided.

[0007] The inspection apparatus may further include time constant adjusting means for controlling the switching means in accordance with a signal designating the frequency of the test signal. Further, the inspection apparatus may further include a measuring unit that measures a timing at which an output level changes at at least one output terminal corresponding to at least one input terminal of the electronic circuit. In this case, the inspection device may further include a determination unit that determines an input level for the electronic circuit to operate normally based on the level of the test signal corresponding to the timing measured by the measurement unit.

According to the present invention configured as described above, an input level test can be performed by one function test, and an electronic circuit can be inspected without being affected by hysteresis characteristics.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining the principle of an electronic circuit inspection method according to one embodiment of the present invention.

FIG. 1A shows the waveform of a rectangular test signal output from an IC tester. Conventionally, for example,
The high level of the square wave test signal is set to 0.
The function test was performed 16 times while changing the voltage from 9 V to 2.4 V. In the present embodiment, the IC
Instead of using a rectangular wave test signal output from a tester or the like, the signal is converted into a test signal having a ramp waveform as shown in FIG. FIGS. 1C and 1D show examples of output signals when a function test is performed by inputting such a test signal into an electronic circuit.

FIG. 1C shows an output signal of the input cell when the input cell constituted by the buffer circuit is inspected. Here, a function test is performed by inputting a ramp signal to the input terminal of the buffer circuit, and the timing at which the output level changes at the output terminal of the buffer circuit is measured. From FIGS. 1B and 1C, the reason why the input cell normally operates is that the high level of the input signal is higher than 1.6 V and the low level of the input signal is 1.V.
It turns out that it is when it is smaller than 6V. in this way,
According to the present embodiment, in one function test,
An input level (range) for a circuit to operate normally can be obtained.

FIG. 1D shows an output signal of the Schmitt trigger circuit when a Schmitt trigger circuit having a hysteresis characteristic is inspected. here,
The function test is performed by inputting a ramp signal to the input terminal of the Schmitt trigger circuit, and the timing at which the output level changes at the output terminal of the Schmitt trigger circuit is measured. From FIG. 1B and FIG. 1D, the reason why the Schmitt trigger circuit operates normally is that the high level of the input signal is 2.0 V at the time of rising of the input signal.
It can be seen that when the input signal falls, the low level of the input signal is lower than 1.2V. As described above, according to the present embodiment, an input level (range) for normal operation of the circuit can be obtained without being affected by the hysteresis characteristics of the circuit.

Next, the configuration of an inspection circuit for an electronic circuit according to an embodiment of the present invention will be described with reference to FIG. 2, a square wave test signal input from an IC tester or the like includes a differential amplifier 10, resistors R _{1 to} R ₃ ,
The integration circuit constituted by the capacitor C ₁ -C ₃ (lamp delay circuit), it is converted to a test signal having a ramp waveform. This integration circuit is connected to the circuit under test 10.
Test signal supply means for supplying the test signal to at least one input terminal of 0 as an input signal. Note that the test signal supply unit may include an oscillator that generates a rectangular wave signal.

In the above integrating circuit, the time constant of integration can be changed by switching the resistors R _{1 to} R ₃ and the capacitors C _{1 to} C ₃ . In the inspection apparatus shown in FIG. 2, a total of nine time constants can be set by switching between three resistors and three capacitors, but more time constants may be set. Switching means 20 is provided for switching the resistances R _{1 to} R ₃ ,
Switching means 30 is provided for switching the capacitor C ₁ -C _3. These switching means may be constituted by mechanical switches (selectors), but in the present embodiment, they are constituted by multiplexers to enable electrical control. In this embodiment, in order to externally control the time constant of the integration circuit, a frequency designation signal is input to the inspection device. This frequency designation signal is stored in the register 40 constituting the time constant adjusting means. Register 40
The switching means 20 and 30 are controlled on the basis of each bit of the frequency designation signal stored in, so that the time constant of the integration circuit is adjusted.

With the above configuration, a desired test signal can be supplied to the circuit under test 100. Circuit under test 1
When a test signal is supplied to at least one input terminal 00, the output level changes at at least one output terminal corresponding to this input terminal. The timing may be measured using a measuring device such as an IC tester or a logic analyzer. In the present embodiment, however, the timing measuring circuit 50 for measuring the timing at which the output level of the circuit under test 100 changes is measured. Is provided. Thereby, the level of the test signal corresponding to the timing at which the output level of the circuit under test 100 changes can be easily measured. For this purpose, the A / D converter 60 converts the test signal supplied to the circuit under test 100 into an A / D signal.
Convert it. Further, in the level determination circuit 70,
By holding the output signal of the A / D converter 60 in response to the trigger signal output from the timing measurement circuit 50, the level of the test signal corresponding to the timing at which the output level of the circuit under test 100 changes is determined. . The level of the test signal may be displayed on the display unit 80. If the trigger signal output from the timing measurement circuit 50 is output to the outside of the inspection apparatus, the level of the test signal corresponding to the above timing can be obtained using a measuring instrument such as a multimeter. is there. In this case, the A / D converter 60, the level determination circuit 70, and the display unit 80 become unnecessary.

[0016]

As described above, according to the present invention, an input level test can be performed by one function test, and an electronic circuit can be inspected without being affected by hysteresis characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of an electronic circuit inspection method according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an inspection circuit of an electronic circuit according to one embodiment of the present invention.

[Explanation of symbols]

10 differential amplifier 20, 30 switching means 40 register 50 timing measuring circuit 60 A / D converter 70 level decision circuit 80 the display unit 100 to be inspected circuit R ₁ to R ₃ resistor C ₁ -C ₃ capacitor

Claims (5)

[Claims] 1. A method for testing an electronic circuit, comprising: inputting a test signal having a ramp waveform to at least one input terminal of the electronic circuit, wherein at least one input terminal of the electronic circuit corresponds to the at least one input terminal. (A) measuring the timing at which the output level changes at one output terminal; and (c) determining whether the electronic circuit operates normally based on the level of the test signal corresponding to the timing measured in (a). (B) obtaining an input level. 2. An apparatus for inspecting an electronic circuit, comprising: an integrating circuit for generating a test signal having a ramp waveform by integrating an input rectangular wave signal, wherein at least one input terminal of the electronic circuit is provided. Test signal supply means for inputting the test signal; switching means for switching a time constant of the integration circuit;
An inspection apparatus comprising: 3. The inspection apparatus according to claim 2, further comprising time constant adjusting means for controlling said switching means in accordance with a signal designating a frequency of the test signal. 4. The electronic circuit according to claim 2, further comprising measuring means for measuring a timing at which an output level changes at at least one output terminal corresponding to said at least one input terminal. Inspection equipment. 5. The apparatus according to claim 1, further comprising a determination unit configured to determine an input level for operating the electronic circuit normally based on a level of a test signal corresponding to the timing measured by the measurement unit. Item 5. The inspection device according to Item 4.