JPH0712887A - Current tester - Google Patents

Abstract

PURPOSE:To facilitate formation of logic pattern and to shorten the test time. CONSTITUTION:The current tester comprises means 5 for detecting the current flowing through an element 3 under test and converting the current into a voltage, a comparator 6 receiving an output from the current/voltage converting means 5 and a reference voltage corresponding to the allowable current of the element 3, and/or a window comparator 7 receiving an output from the current/voltage converting means 5 and second and third reference voltages corresponding to the current levels for setting the upper and lower limits of allowable current range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current test device,
Particularly, it is preferably used for testing analog switches and the like in which ON / OFF of current is controlled in synchronization with a logic signal.

[0002]

2. Description of the Related Art FIG. 4 is a diagram schematically showing a test method by a conventional current test apparatus.

In FIG. 1, reference numeral 1 denotes a semiconductor integrated circuit to be tested, which has a built-in logic circuit section 2 which operates by a digital signal from the outside and an analog switch 3 which operates by a signal from the logic circuit section 2. ing. Further, one of the analog switches 3 is connected to a specific potential (for example, GND) in the semiconductor integrated circuit 1 or the output of an amplifier, and the other is connected to the terminal 4 so that it can be output to the outside.

When the analog switch portion of such a semiconductor integrated circuit is tested, a digital pattern signal for setting the ON or OFF state thereof is created or a pattern hold is performed in the middle of a series of digital pattern signals. I was doing a test.

Furthermore, the ON resistance and O of the analog switch
When evaluating leakage current during FF, external voltage source 5
Then, a known voltage was applied, and the value was measured by the ammeter 6 for evaluation.

[0006]

As shown in the above-mentioned conventional example, in order to confirm the operation of the analog switch or the like, it is necessary to create a digital pattern signal or hold the digital pattern signal, and the logic section is complicated. The more time it takes to create a logic pattern signal for the test, the more time it takes.

Further, in the case of evaluating an analog switch or the like, current measurement is required as described above. However, DC-like measurement such as this current measurement requires setup time and leakage current. It takes a lot of time to set up the measurement of the minute current as described above, which leads to the lengthening of the test time. Further, in order to obtain the DC-like characteristic, the time for holding the logic pattern signal as described above also increases.

The present invention makes it possible to measure the DC characteristics of an analog switch or the like controlled by a digital signal as a digital function without preparing a special logic pattern, and simplify the creation of the logic pattern. Furthermore, it is an object of the present invention to further shorten the test time by determining the DC characteristic with a logic pattern.

[0009]

SUMMARY OF THE INVENTION A current test apparatus of the present invention comprises a current-voltage converting means for detecting a current flowing through a device under test and converting the voltage into a current, an output of the current-voltage converting means and the device under test. And a comparator to which a reference voltage corresponding to the allowable current is input.

Further, the current test apparatus of the present invention detects the current flowing through the device under test and converts the current to voltage, and the output of the current voltage conversion device and the allowable current range of the device under test. A window comparator to which first and second reference voltages corresponding to current values defining upper and lower limits are input.

Further, the current test apparatus of the present invention corresponds to the current-voltage converting means for detecting the current flowing in the device under test and converting the current into the voltage, the output of the current-voltage converting device and the allowable current of the device under test. A first reference voltage that is input, a second and third reference voltage corresponding to the current value that defines the upper limit and the lower limit of the output of the current-voltage converting means and the allowable current range of the device under test. And a window comparator to which is input.

Further, the current testing device of the present invention comprises a current-voltage converting means for detecting a current flowing in the switch element and converting the current into a voltage, an output of the current-voltage converting means and an allowable current when the switch element is off. A comparator to which the corresponding first reference voltage is input, and second and third corresponding to current values that define the upper limit and the lower limit of the allowable current range when the output of the current-voltage converting means and the switch element are turned on. And a switch means for switching and outputting the output of the comparator and the output of the window comparator in accordance with the ON / OFF state of the switch element. .

[0013]

The current test apparatus of the present invention corresponds to the current-voltage converting means for detecting the current flowing in the device under test and converting the current into the voltage, the output of the current-voltage converting device and the allowable current of the device under test. By providing a comparator to which the reference voltage is input, the test regarding the allowable current of the device under test is performed.

Further, the current test apparatus of the present invention detects the current flowing through the device under test and performs current-voltage conversion, and the output of the current-voltage conversion device and the allowable current range of the device under test. By providing a window comparator to which the first and second reference voltages corresponding to the current values defining the upper limit and the lower limit are input, the test regarding the allowable current range of the device under test is performed.

The current test apparatus of the present invention corresponds to the current-voltage converting means for detecting the current flowing in the device under test and converting the current into the voltage, the output of the current-voltage converting device and the allowable current of the device under test. A first reference voltage that is input, a second and third reference voltage corresponding to the current value that defines the upper limit and the lower limit of the output of the current-voltage converting means and the allowable current range of the device under test. By providing a window comparator to which and are input, a test regarding the allowable current and the allowable current range of the device under test is performed.

Further, the current testing device of the present invention comprises a current-voltage converting means for detecting a current flowing in the switch element and converting the current into a voltage, an output of the current-voltage converting means and an allowable current when the switch element is off. A current-voltage converter that performs a current test when the switch element is off and detects the current flowing in the switch element by a comparator to which the corresponding first reference voltage is input, and performs current-voltage conversion, and this current-voltage converter. A switch comparator is turned on by a window comparator to which the output of the conversion means and the second and third reference voltages corresponding to the current value that defines the allowable current range when the switch element is turned on are input. The test result when the switch element is turned on and off is selectively selected by the switch means that switches and outputs according to the on / off state of the switch element. It is intended to be able to force.

With the above configuration, the DC characteristic current measurement can be replaced with the logic pattern, the digital pattern for DC measurement and the hold of the digital pattern are eliminated, and the digital pattern can be easily created.
In addition, the current measurement time changes from DC to a logic pattern, so that the test time can be shortened.

[0018]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the current test apparatus of the present invention. As shown in the figure, a semiconductor integrated circuit 1 as a circuit under test has a digital circuit block 2 driven by a logic pattern signal from the outside and an analog switch 3 controlled by the output of the digital circuit block 2. , One of the analog switches 3 is connected to a specific potential (for example, bias potential, GND) in the semiconductor integrated circuit, the output of the amplifier, etc. (even if it is output to the outside), and the other is connected to the output (input) terminal 4. It is connected.

The current test apparatus of this embodiment receives the current-voltage converter 5 connected to the output (input) terminal 4 of the semiconductor integrated circuit 1 and the voltage output of this current-voltage converter 5, and further inputs An external reference voltage (Ref1) is input, and the voltage output of the current-voltage converter 5 is input, and an external reference voltage (R
ef2, Ref3) as an input, and a switch circuit 8 that receives the output of the comparator 6 and the output of the comparator 7 and switches between these two inputs with an external logic pattern input from the terminal 9. The measurement result is guided to the output terminal 10.

FIG. 2 is a diagram showing in detail an example of the window comparator section and the switch circuit after the current-voltage converter of this embodiment. The window comparator unit 7 uses a reference voltage Ref2 input from the outside as an input of an inverting input terminal (−) and a voltage output of the current-voltage converter 5 as an input of a non-inverting input terminal (+), and a comparator 11.
A reference voltage Ref3 input from the outside is used as an input of the non-inverting input terminal (+), and a voltage output of the current-voltage converter 5 is used as an input of the inverting input terminal (-). 12 and the logic circuit 13 of the logical product which inputs the output.

The switch circuit 8 is composed of a logic circuit here, and the output of the window comparator 7 and the terminal 9 are provided.
An AND circuit 15 to which an external logic signal input from the external logic signal is input, and an AND circuit 14 to which the output of the comparator 6 and a signal obtained by inverting the external logic signal input from the terminal 9 are input, AND circuits 14 and 15
And an OR circuit 17 to which the output of 1 is input.

The magnitude relationship between the reference voltages Ref1 to Ref3 is such that Ref3>Ref2> Ref1 holds, and the characteristic of the current-voltage converter 5 is that the voltage increases as the amount of current increases. There is. Also, terminal 9
The logic input from the outside is the "L" level signal when the analog switch 3 is OFF and the "H" level signal when the analog switch 3 is ON.

Here, the semiconductor integrated circuit 1 to be the circuit under test
A measurement operation when the digital pattern signal is input to the analog switch 3 and the analog switch 3 is turned on / off will be described. Now, the analog switch 3 is turned on by the logic operation.
When performing FF, the characteristics of the analog switch are ON /
Along with the OFF operation, the leakage current at the time of OFF becomes a problem. When this non-defective standard value of the leakage current was as I _1, the current I ₁ current - voltage converted by the voltage converter 5 R
If ef1 is set (the reference voltage input to the inverting input terminal (−) of the comparator 6 is the same R as described above.
ef1), if the analog switch 3 is turned off and the actual leak current I is less than or equal to the standard value I _{1, the} voltage V at which the leak current I is current-voltage converted is V <Ref1.
And the output of the comparator 6 becomes "L" level.

If the leak current is large even though the analog switch 3 is off or if the analog switch 3 is turned on due to an abnormal operation, the analog switch 3
The electric current I flowing through the circuit becomes large, V> Ref1, and the output of the comparator 6 becomes "H" level.

Here, from the terminal 9, the analog switch 3
A signal indicating the ON / OFF state of is input. When the analog switch 3 is OFF, the expected value is terminal 9
Since the "L" level signal is input to the output terminal 1,
The result of the comparator 6 is output to 0.

Next, when the analog switch 3 is turned on by a logic operation, the switch characteristics are the ON operation and the ON resistance at the time of ON. When the standard of this ON resistance characteristic is R _{3 to} R ₂ , the current limited by R ₃ is I ₃ , and the current limited by R ₂ is I ₂ , the current I ₃ is the current-voltage converter 5. the voltage to be converted Ref3, current I ₂ current - voltage converted by the voltage converter 5 and Ref2 (as described above, the inverting input terminal of the comparator 11 (- reference voltage input to) the Ref2 The reference voltage that is set and input to the non-inverting input terminal (+) of the comparator 12 is Ref
3). Also, the analog switch 3 is actually O
The ON resistance at the time of N is R, the current limited by the ON resistance R is I ′, and the voltage converted by the current-voltage converter 5 is V ′.

The analog switch 3 is turned on to turn on the resistance R.
Is within the standard of R _{2 to} R ₃ , the current I ′ is I _{2 to} I ₃
Then, the voltage V ′ satisfies Ref2 <V ′ <Ref3, the output of the comparator 11 becomes “H” level, the output of the comparator 12 becomes “H” level, and the AND circuit 13
Output becomes "H" level. The ON resistance R is the standard R
When it is smaller than ₃ , the current I'is I '> I ₃ , the voltage V'is V'> Ref3, the output of the comparator 11 is "H" level, the output of the comparator 12 is "L" level, and the AND circuit The output of 13 becomes "L" level. On the contrary, when the ON resistance R exceeds the standard R ₂ , the current I ′ becomes I ′ <I ₂ , the voltage V ′ becomes V ′ <Ref2, the output of the comparator 11 is “L” level, and the output of the comparator 12 is Becomes "H" level, and AND circuit 1
The output of 3 becomes "L" level. Here, a signal indicating the ON / OFF state of the analog switch 3 is input from the terminal 9, and when the analog switch 3 is ON, an “H” level signal is input as an expected value, so the output terminal 10 The result of the window comparator 7 is output to.

From the above, by using the present invention,
The leak current of the analog switch is measured in real time without using a logic pattern hold, etc., the result of “L” level when OFF and “H” level when ON is included in the analog information, Can be obtained from 10.

Further, an embodiment obtained by expanding the above embodiment is shown in FIG.
Shown in. As shown in FIG. 3, in the present embodiment, the exclusive OR circuit 18 having the output of the switch circuit 8 and the signal of the expected value input terminal 9 as an input, and the latch circuit having the output of the exclusive OR circuit 18 as an input Equipped with 20. Reference numerals 19 and 21 denote output terminals of the exclusive OR circuit 18 and the latch circuit 20, respectively. With this configuration, if the object to be tested is a good product,
Since the expected value input from the terminal 9 and the output of the switch circuit output from the terminal 10 are equal, a signal of "H" level is always output from the terminal 19, but "L" in the case of failure. The level signal is output in real time. By inputting this signal to the latch circuit 20, the latch circuit 2
When 0 is switched from the “H” level to the “L” level, the defective state is stored. Therefore, after performing all the logic patterns in real time, it is possible to judge whether the test object is good or bad simply by measuring the result of the terminal 21.

[0031]

As described in detail above, according to the current test apparatus of the present invention, in the device under test such as the analog switch whose analog current changes in synchronization with the logic signal, the device under test is , A current-to-voltage converter, a comparator or / and a window comparator,
Alternatively, by connecting to the current-voltage converter, the comparator, the window comparator, and the switch means, it is possible to measure in real time without stopping the operation of the logic pattern, and the test time can be shortened.

Furthermore, it is possible to set a standard for the amount of current to be measured, and it is possible to determine whether the current is good or bad depending on the magnitude of the current.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a current test device of the present invention.

FIG. 2 is a diagram showing in detail an example of a window comparator unit and a switch circuit after the current-voltage converter of this embodiment.

FIG. 3 is a diagram showing a circuit connected to a subsequent stage of a switch circuit of the current test device of FIG.

FIG. 4 is a diagram schematically showing a test method using a conventional current test device.

[Description of symbols] 1 semiconductor integrated circuit 2 digital circuit block 3 analog switch 4 output (input) terminal 5 current-voltage converter 6 comparator 7 window comparator 8 switch circuit 9 logic pattern input terminal 10 output terminal

Claims (4)

[Claims] 1. A current-voltage converting means for detecting a current flowing through a device under test and converting the current into a voltage, an output of the current-voltage converting device and a reference voltage corresponding to an allowable current of the device under test are input. A current test device including a comparator. 2. A current-voltage converting means for detecting a current flowing through a device under test and performing current-voltage conversion, and an output of the current-voltage converting device and a current defining upper and lower limits of an allowable current range of the device under test. And a window comparator to which the first and second reference voltages corresponding to the values are input, and a current test device. 3. A current-voltage converting means for detecting a current flowing through a device under test and converting the current into a voltage, and an output of the current-voltage converting device and a first reference voltage corresponding to an allowable current of the device under test. , And a window comparator to which the output of the current-voltage converting means and the second and third reference voltages corresponding to the current values defining the upper and lower limits of the allowable current range of the device under test are input. And a current test device equipped with. 4. A current-voltage converting means for detecting a current flowing through a switch element and converting the current into a voltage, and a first reference voltage corresponding to an output of the current-voltage converting means and an allowable current when the switch element is turned off. A comparator to which is input, an output of the current-voltage conversion means, and second and third reference voltages corresponding to current values that define the upper limit and the lower limit of the allowable current range when the switch element is turned on are input. And a switch means for switching and outputting the output of the comparator and the output of the window comparator according to the ON / OFF state of the switch element.