JPH05273299A - Circuit inspection method - Google Patents

Abstract

PURPOSE:To measure the load characteristic of a DUT with good accuracy. CONSTITUTION:The following are installed: an active load 30; a reference- voltage generator 10 which applies a commutation voltage to an input terminal at the active load 30; and a DC module 60 which is connected to an output terminal via a switch means, which sets an arbitrary voltage and which can measure an electric current flowing across the output terminal and an object under test. A first offset voltage VOF12 on the side of a diode connected to a first constant-current source is found. A second offset voltage VOF34 on the side of a diode connected to a second constant current source is found. An operation treatment by which voltages DELTAV12, DELTAV34 are added to the first offset voltage VOF12 and the second offset voltage VOF34 so as to equally change the electric current of each diode by DELTAI in such a way that the absolute value of the difference between the VOF12 and the VOF34 is converged to a voltage VJUDGE in a definite range. On the basis of the operation treatment, the offset voltage VOFD of the active load is found.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit inspection method for inspecting load characteristics of, for example, an LSI, and more particularly to a circuit inspection method capable of accurately measuring load characteristics.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram for explaining a conventional circuit inspection method. In the figure, 10 is a reference voltage generator, which is connected to an active load 30 via an amplifier 20. In the active load 30, the first constant current source CC1 is connected to the common connection point on the anode side of the diode bridge 31, and the second constant current source CC2 is connected to the common connection point on the cathode side. Are connected.

Reference numeral 40 is an object to be inspected (hereinafter referred to as DUT) connected to the output terminal of the active load 30. The current values of the first and second constant current sources CC1 and CC2 can be controlled by a voltage applied from the outside, and the reference voltage generator 10 is used to activate the active load 3.
Based on the commutation voltage V _COM applied to 0,
The current I _OL is supplied to the DUT 40, or the current I _OH flows out from the DUT 40.

[0004]

In such a conventional circuit inspection method, since the characteristics of the diodes forming the diode bridge have variations, the voltage V _DUT and the reference voltage generation for the load test of the _DUT are generated. There is a problem that an error is generated between the communication voltage V _COM applied from the device and the load characteristics cannot be accurately measured.

The present invention has been made in view of the above points.
A DC module for applying a reference voltage.
Installed on the output terminal side of the bridge
Pressure V _COM It is designed to correct the load characteristics of the DUT.
Provides a circuit inspection method that can accurately measure
The purpose is to do.

[0006]

[Means for Solving the Problems]
For this purpose, the present invention is based on the anode side of the diode bridge.
Connect the first constant current source to the common connection point of
Connect a second constant current source to the common connection point on the
Object to be inspected connected to the output terminal of diode bridge
An active load that supplies and drains a constant current to the
The object to be inspected is connected to the input terminal of the diode bridge.
Communication voltage that becomes the threshold of the current flowing through the
A reference voltage generator for applying a pressure, and the diode
Connected to the output terminal of the bridge via switch means.
Set the desired voltage, and
A direct current that can measure the current flowing between inspection objects
Flow module, and the current of the second constant current source is
In the state of zero, the current value detected by the DC module is
The community when the current of the first constant current source becomes 1/2
Voltage difference between the DC voltage and the DC module
First offset voltage on the diode side connected to the current source
V_OF12And the current of the first constant current source
Is zero, the current value detected by the DC module
Is a half of the current of the second constant current source,
-The voltage difference between the
The second offset voltage on the diode side connected to the constant current source.
Pressure V_OF34And the first and second constant currents
According to the current value arbitrarily set in the source, the V_OF12And V
_OF34The absolute value of the difference between the voltage V within a certain range_JUDGEConverge to
The first offset voltage V_OF12And the second
Offset voltage V_OF34The current of each diode is equal to Δ
The voltage ΔV is changed so that only I changes.₁₂, ΔV₃₄Performance to add
Based on the step of performing the arithmetic processing, the voltage V_JUDGEConverge to
Offset voltage of the diode bridge from each voltage value
Pressure V_OFDThe offset voltage V_OFDBy the correction of
The object to be inspected with a precise and accurate commutation voltage.
It is characterized by supplying and discharging a check current.

[0007]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration block diagram for explaining a circuit inspection method showing an embodiment of the present invention. In the figure, components having the same functions as those in FIG.
Hereinafter, the same applies in the drawings.

Reference numeral 10 is a reference voltage generator, and 11 is a data correction unit, which corrects the voltage data of the commutation voltage V _COM set in the active load 30. De - the data correcting unit 11, 11 ₁ the address bus 51 and de to CPU 50 - in Taserekuta, Komyute - - De connected via a data bus 52 Deployment voltage V _COM voltage de - data DA
₁ and correction data DA _{2 and} DA ₃ for correcting the gain and offset of the voltage data DA ₁ are input from the CPU 50.

[0009] The de - Taserekuta 11 _1, voltage de - data DA
₁ is output to the first register 11 ₂ , the gain correction data DA ₂ is output to the second register 11 ₃ , and the offset correction data DA ₃ is output to the third register 11 ₄ .

11_Five Is each register 11_{1, 2, 3} Entered from
Data D_{1, 2, 3} Correction calculation that performs correction calculation based on
For example, DA₁ * DA₂ + DA₃ Such as
Done _,The result is output to the DA converter 12. DA conversion
The device 12 transmits the analog converted data via the amplifier 13.
To the input terminal a of the diode bridge 31 for communication.
Voltage V_COM Is applied as. 14 is a current adjusting means
Then, the first and second current sources CC in the active load 30
Current I output by 1,2_OL,_OH Adjust the size of.

Reference numeral 60 is a DC module (hereinafter referred to as DC module).
The voltage V for performing the load test of the DUT 40
It is for correcting the error between the _DUT and the commutation voltage V _COM applied from the reference voltage generator 10, and is connected to the output terminal b of the diode bridge 31 via the relay 61. DC module 60,
CPU 5 via address bus 51 and data bus 52
It is connected to 0 and the voltage V is controlled by the CPU 50.
_DC is set to the output terminal b, and the current I _DC flowing between the output terminals b is measured.

When the relay 61 is turned on with the DUT 40 disconnected, the DC module 60 applies an arbitrary voltage V _DC to the output terminal b and to the input terminal a based on a command from the CPU 50. The current value I _DC that changes depending on the relationship with the commutation voltage V _COM is continuously measured. The CPU 50 changes the data DA ₂ , 3 of the second and third registers 11 ₃ , ₄ on the basis of the current value I _DC obtained by the DC module 60, and the commutation voltage V DC.
Correct _{CO M.}

FIG. 2 shows an actuator._IShow Broad Extracted
The circuit diagram shows the correction operation of the diode bridge.
It is for the sake of clarity. D in the figure₁~ D_FourIs a diode
It is a diode that constitutes a bridge. The diode is
The current represented by the following equation (1) approximately flows. Each diode
Current flowing in ₁~ I_FourThen each diode is
From (1), a current flows as shown in the following equations (2) to (5).
It

[Equation 1] Further, between the diode D ₁ and the diode D ₂ , I _OL
Since the relationship of = I ₁ + I _{2 is established,} the relationship of Expression (6) is obtained from Expressions (2) and (3). On the other hand, since the relation of I _OH = I ₃ + I ₄ is established between the diode D ₃ and the diode D ₄ , the relation of the formula (4) and the formula (5) is obtained. ..

[Equation 2]

FIG. 3 shows the relationship between the voltage and the current.
The horizontal axis indicates V _COM -V _DUT , and the vertical axis indicates I ₁ and I ₃ . FIG. 3 shows a case where the current values of the first constant current source CC1 and the second constant current source CC2 are different. In this example, the first constant current source CC1 is 10 mA, 3 shows the case where the constant current source CC2 of 5 mA is 5 mA. If the characteristics of each diode constituting the diode bridge 31 are completely equal, when V _COM and V _DUT are equal, I _DC
While current flows through the 2.5mA is, as described above, since there are variations in each diode, actually different current (I ₁₀ -I ₂₀₎ as shown in FIG flows.

Looking at the variation between the diodes with respect to the diode D ₁ and the diode D ₂ , V _COM −V _DUT =
When lnI _s2 −lnI _s1 , it is a balance point (point A) at which a current equal to the diodes D ₁ and ₂ flows, and the voltage V _OF12 at this time is
Is the offset due to the diodes D _{1, 2} . On the other hand, in the diode D ₃ and the diode D ₄ , V _COM −V _DUT
= LnI _s3 −lnI _s4 is a balance point (point B) at which a current equal to that of the diodes D ₃ and ₄ flows, and the voltage V at this time is
_OF34 is an offset due to the diodes D _{3 and 4} .

As can be seen from FIG. 3, the current amount is changed by ΔI from the points A and B in the direction of the arrow by ΔI, that is, the voltage value (V _COM −V _DUT ) is changed so as to maintain the difference of 2.5 mA, and the voltage is changed. if you find a point (V _{C OM} -V _DUT) matches, the diode bridge 31 total offset voltage V _OFD is obtained. Since the rate of change of the width of a certain range around the offset voltage V _OFD is small, this range is regarded as an offset voltage V _OFD as a convergence range, and the voltage in this range is hereinafter referred to as a judgment voltage V _JUDGE .

Next, the correction method described in FIG. 3 will be described in the actual process based on the apparatus shown in FIG. (1) _{Obtain the} offset voltage V _OF12 due to the diodes D _{1 and 2}
Process First, the current of the first constant current source CC1 is set to 10 mA and the second constant current source CC2 is set to 0 mA. next,
With the DUT 40 removed, the relay 61 is turned on, and 0 V is applied from the DC module 60 to the output terminal b. At this time, the DC module 60 is in a state of being able to measure the current I _DC that changes with the change of the commutation voltage V _COM .

In this state, the CPU 50 sets the data DA _{1 in} which the commutation voltage V _{C OM} becomes 0 V in the first register 11 ₂ and the data DA ₂ of gain × 1 in the second register 11 _3. Set. The direct measurement to the current value I _{D C} of the module 60 to change the offset data DA ₃ of the third register 11 ₄ so that CC1 / 2, corrects the commutation voltage V _COM.

The CPU 50 stores the data DA ₃ when the current value I _DC becomes CC _1/2 in the memory as the offset voltage V _OF12 .

(2) Obtain the gain of the diode bridge
Process Subsequently, the CPU 50 gives the DC module 60 an instruction to apply a voltage of 5V to the output terminal b. In this state,
The CPU 50 sets the data DA _{1 in} which the commutation voltage V _{C OM} becomes 0 V in the first register 11 ₂ and the second register so that the current value I _{D C} detected by the DC module 60 becomes CC 1/2. The gain data DA ₂ of 11 ₃ is changed.

When the current value I _DC becomes CC1 / 2, CP
The U50 stores the data DA ₂ as gain data V _GAIN in the memory.

(3) When the process formula (6) for obtaining k * T / q is differentiated with respect to I ₁ , the following formula (8) is obtained.

[Equation 3] This equation (8) shows the amount of change in the current with respect to the voltage, and shows the slope of FIG. In order to obtain k * T / q, the voltage is shifted in the plus and minus directions by a small voltage ΔV with respect to 5V, and the change amount Δ of the current I _DC at that time is changed.
I _DC is measured by the DC module 60. ΔV changed by the first register 11 ₂ and the DC module 6
Substituting ΔI _DC measured by 0 into the equation (8), k * T / q is obtained. That is, the value obtained by multiplying (2ΔV / ΔI _DC ) by CC1 / 4 is k * T / q. Note that k * T / q can also be obtained by measuring the temperature T because k and q are constants.

(4) Offset voltage due to the diodes D _{3 and 4}
After measuring the process k * T / q for _obtaining V _OF34 , the CPU 50 sets the current of the first constant current source CC1 to 0 mA, and the second constant current source CC2
Is set to 10 mA. Then, the offset voltage V _OF34 of the diodes D _{3 and 4} is obtained and stored in the memory by the same procedure as the process (1).

(5) Offset of diode bridge 31
The respective data obtained in the processes (1) to (4) of the arithmetic processing for _{obtaining the} voltage V _OFD is set from the memory to the arithmetic processing unit for performing the operations of the following equations (9) and (10).

[Equation 4] FIG. 4 is a time chart showing the operation of the arithmetic process. The arithmetic processing unit treats the following as variables and performs an arithmetic operation in which the offset voltage V _OF12 and the offset voltage V _OF34 converge to the judgment voltage V _JUDGE of the diode bridge.

It should be noted that ΔI is a constant, which is the minimum change amount of the current that is changed when the offset voltage V _OFD of the diode bridge is obtained as described in FIG. V _12x is a variable that changes with ΔV ₁₂ that changes ΔI, and the offset voltage V _OF12 on the side of the diodes D _{1 and 2} becomes the initial value (hereinafter, X = 1 to n, and when X = 1, the initial value Is). A variable that varies with [Delta] V ₃₄ to vary the V _34x [Delta] it, the offset voltage V _OF34 of the diode D _{3, 4} side is the initial value. I _1x is the current flowing in the diode D ₁ and is a variable of ΔI,
_IOL / 2 is the initial value. I _3x current flowing in diode D ₃ is a variable of ΔI,
I _OH / 2 is the initial value. ΔV _12X voltage value that changes the current flowing through the diode D ₁ by ΔI ΔV _34X voltage value that changes the current flowing through the diode D ₃ by ΔI

Initial values are assigned to the variables (step 1). V ₁₂₁ > V ₃₄₁ is compared, and if larger, ΔI is defined as a negative constant, and if smaller, defined as a positive constant (step 2). | V ₁₂₁ −V ₃₄₁ | is compared with the magnitude of the judgment voltage V _JUDGE (step 3). If | V ₁₂₁ −V ₃₄₁ | is smaller than the judgment voltage V _JUDGE , (V ₁₂₁ −V ₃₄₁ ) / 2 is calculated to be the offset voltage V _OFD of the diode bridge (step 4).

| V ₁₂₁ −V ₃₄₁ | is the judgment voltage V
If it is larger than _JUDGE , the calculation is performed by the equations (9) and (10) to obtain ΔV ₁₂₁ and ΔV ₃₄₁ (steps 5 and 6). The obtained ΔV ₁₂₁ and ΔV ₃₄₁ are the initial voltage V _121,
It is added to V ₃₄₁ (steps 7 and 8). The change ΔI is also added to the currents I _1x and I _3x (steps 9 _and 10).

Returning to step 3, the magnitudes of the voltages V ₁₂₂ and V _{342 obtained} by adding ΔV ₁₂₁ and ΔV ₃₄₁ are compared. If _{│V 122} -V ₃₄₂ │ is larger than the judgment voltage V _JUDGE , the processes of steps 5 and 6 are repeated again. At this time, I _1X and I _3X are Δ in Steps 9 and 10.
Numerical values I ₁₂ and I ₃₂ to which I is added are used.

[0029]

As described in detail above, the circuit inspection method of the present invention is such that the offset of the diode connected to the first constant current source side and the offset of the diode connected to the second constant current source side. Since the offset of the diode bridge is calculated and corrected on the basis of the above, it is possible to obtain an accurate commutation voltage according to the change of the first and second constant current sources. Therefore, DU
The load characteristic of T can be accurately measured.

[Brief description of drawings]

FIG. 1 is a configuration block diagram illustrating a circuit inspection method according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an active load extracted.

FIG. 3 is a diagram showing a relationship between (V _COM −V _DUT ) and I ₁ and I ₃ .

FIG. 4 is a time chart showing the operation of an arithmetic process.

FIG. 5 is a configuration block diagram showing a conventional circuit inspection method.

[Explanation of symbols]

10 Reference voltage generator 30 Akti _Lee broad 50 CPU 60 DC module - Le

Claims (1)

[Claims] 1. A common on the anode side of a diode bridge.
Connect the first constant current source to the connection point and
Connect a second constant current source to the common connection point on the
-Constant for the inspected object connected to the output terminal of the bridge
The active load for supplying and discharging current, and the input terminal of the diode bridge, the object to be inspected
Communication that is the threshold of the current flowing through an object
A reference voltage generator for applying a voltage, and a switch means at the output terminal of the diode bridge.
Connected and set any voltage, and
Measuring the current flowing between the force terminal and the object to be inspected
And a direct current module capable of controlling the direct current module.
The current value detected by the juule is 1 of the current of the first constant current source.
Commutation voltage and DC module when becoming 1/2
Connected to the first constant current source for the voltage difference with the diode.
First offset voltage V _OF12 Process to obtain as
And when the current of the first constant current source is zero,
The current value detected by the juule is 1 of the current of the second constant current source.
Communication voltage and DC module when becoming 1/2
The voltage difference between the diode and the diode connected to the second constant current source.
Second offset voltage V _OF34 Process to obtain as
And a current value arbitrarily set to the first and second constant current sources
According to the above V _OF12 And V _OF34 The absolute value of the difference between
Pressure V _JUDGE The first offset voltage so that
Pressure V _OF12 And the second offset voltage V _OF34 In each dio
The voltage Δ so that the current of the card changes evenly by ΔI.
V ₁₂ , ΔV ₃₄ Based on the step of performing the arithmetic processing for adding _JUDGE From each voltage value when it converges to
Offset voltage of the ion bridge V _OFD Ask for this
Offset voltage V _OFD Accurate community by correction of
Supply and flow the inspection current to the inspected object
A circuit inspection method characterized by issuing.