JP3071875B2 - IC test equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC test apparatus,
An IC for measuring a transient response time T required for a change of an output signal level according to the input signal to reach a predetermined ratio when a predetermined input signal is given to an IC to be tested. Test equipment.

[0002]

2. Description of the Related Art An electronic circuit using an IC such as a microcomputer, a memory, and a logic circuit is required to obtain an expected output signal when an input signal is applied. In an IC test apparatus for testing whether or not such a request is satisfied, a test is usually performed by giving a predetermined periodic test pattern as an input signal and analyzing a waveform pattern of an output signal obtained at this time. Is going. In particular, when a step-like input signal is given to an IC to be tested, it is important to analyze a transient characteristic of a change in an output signal according to the input signal. For example, consider a case where an input signal that rises in a stepwise manner from 0 V to 5 V is given and an output signal that rises from 0 V to 5 V is obtained. The transient characteristic in this case is quantitatively determined based on data indicating how long it took, for example, from the time when the input signal rises to the time when the output signal rises to 50%. That is, by measuring the transient response time T required until the change of the output signal level according to the input signal reaches a predetermined ratio (in this case, 50%), a quantitative analysis of the transient characteristics becomes possible.

[0003]

In the conventional IC test apparatus, a target output signal level is set in advance in order to measure the transient response time T as described above.
It is necessary to determine the time until the output signal reaches this target level. For example, in the above example, the output signal is 5
The target level when rising to 0% is 2.5V. Therefore, the operator sets the target level to 2.
A setting operation of 5 V must be performed. In addition, in order to perform a test on an IC capable of obtaining an output signal whose output signal rises from 0V to 3V, it is necessary to change the target level to 1.5V. For this reason, when testing various ICs, there is a problem that the work load of the operator is heavy. Further, although the output signal should originally change from 0V to 5V, the output signal may actually change from 0.1V to 5.2V due to the fluctuation of the power supply voltage.
When the target level is set to 2.5 V, a correct transient response time T cannot be obtained.

Accordingly, an object of the present invention is to provide an IC test apparatus capable of obtaining an accurate transient response time T with a simple operation.

[0005]

According to the present invention, when a predetermined input signal is supplied to an IC to be tested, a change in an output signal level according to the input signal reaches a predetermined ratio. In an IC test apparatus for measuring a transient response time T required until, an input signal generating means for generating a predetermined input signal to be supplied to the IC, and an output waveform capturing means for capturing a waveform of an output signal output from the IC. , Prescribed
Of the input signal at the reference time t0.
, The period before the output signal still shows a change
Any time t1 expected to be medium and the input signal
And the output signal changes, and the change is sufficiently stable
Time setting method for setting any time t2 expected to be
The time t1 for the output waveform captured by the output waveform capturing means, the ratio setting means for setting the change rate x of the output signal level defining the transient response time to be measured,
At the time t2 and the level L2 at the time t2.
And the output levels L1 and L2 are proportionally divided by the change rate x to obtain a target level L for the target level calculating means for obtaining the target level L and a target level for the output waveform captured by the output waveform capturing means. Time t when L is reached
And calculate the time from the reference time t0 to the time t,
And a transient response time calculating means for obtaining the transient response time T to be measured.

[0006]

In the IC test apparatus according to the present invention, predetermined times t1 and t2 are set in the time setting means.
Here, time t1 is an arbitrary time that is expected to be in a period before the output signal still shows a change after the input signal is applied, and time t2 is a time when the output signal changes due to the input signal being applied. And any time at which the change is expected to be sufficiently stable. In other words, the change in the output signal at time t1 is expected to be 0%, and the change in the output signal at time t2 is expected to be 100%. The target level calculating means has a function of automatically calculating the target level by using the level values L1 and L2 of the output signal actually measured at these two times. Therefore, the conventional I
There is no need for the operator to set the target level as in the C test apparatus. Further, even when the voltage value corresponding to 0% and the voltage value corresponding to 100% of the output signal change, the target level is always calculated based on the level of the actually measured output signal. In any case, an accurate target level can be set.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a block diagram showing a basic configuration of an IC test apparatus according to the present invention. This device has a function of obtaining a transient response time T for an IC 10 to be tested. The basic components of this IC test apparatus are an input signal generating means 20 for generating a step-like input signal to be supplied to an IC 10 to be tested, and an output waveform capturing means for capturing a waveform of an output signal output from the IC 10. 30
And a computer 40 for analyzing the waveform of the output signal. As the input signal generating means 20, any device can be used as long as it can generate a predetermined input signal. The output waveform capturing means 30 may be an apparatus having an A / D converter for converting an analog signal output from the IC 10 into a digital signal, and having a function of inputting the converted digital signal to the computer 40. Any configuration may be used.

In the figure, the configuration of the computer 40 is shown by four functional blocks. That is, the time point of the step change of the input signal is set as the reference time t0, and the predetermined time t
Time setting means 41 for setting 1 and t2, and a change rate x of an output signal level for defining a transient response time to be measured
Ratio setting means 42 for setting the output waveform and output waveform capturing means 30
The level L1 at the time t1 and the level L2 at the time t2 are obtained for the output waveform captured by the above, and the target level L is obtained by proportionally dividing the output levels L1 and L2 by the change rate x. For the output waveform captured by the calculating means 43 and the output waveform capturing means 30, a time t at which the target level L is reached is determined, and a time from the reference time t0 to the time t is defined as a transient response time T to be measured. This is the transient response time calculation means 44 to be obtained. Actually, each of these blocks is realized by hardware constituting a computer and software for operating the same.

Next, the operation of this device will be described based on a more specific embodiment. Now, for example, consider a case in which the input signal generating means 20 generates an input signal A which changes in a step-like manner as shown in FIG. 2 and supplies this to the IC 10 to be tested. The input signal A is a step signal that instantaneously rises from 0 V to 5 V at time t0 (although it is impossible to generate such a signal in an actual circuit, here, such an ideal signal is used for convenience). It is assumed that a typical step signal is generated). When such an input signal A is applied, an output signal B as shown in FIG. 2 is obtained from the IC 10, for example. As described above, the signal output from the IC 10 is in a form in which the input signal is blunt. An object of the IC test apparatus according to the present invention is to measure a transient response time T required for a change in the level of the output signal B to reach a predetermined rate. For example, assume that 50% is set as a predetermined ratio. In this case, the level of the output signal B is 0 V
５5V, this change is 0% -100%
Considering the change, the time at which the voltage reaches 50% of 2.5 V is time t in the figure, and the required transient response time T is the time from time t0 to time t.

Here, for reference, how the transient response time T is measured in the conventional IC test apparatus will be briefly described. First, the operator sets a target level at which the level change of the output signal becomes 50% as a voltage value. That is, the output signal is 0V
Expected to change to ~ 5V, target level 2.5V
Set a voltage value. And the computer 40
The captured output waveform B is analyzed, and a time t at which the voltage value becomes 2.5 V is obtained. Thus, the transient response time T can be obtained. However, in such a conventional apparatus, an operation of setting a target level by an operator is required. When performing measurement using different voltage levels, it is necessary to set the target level each time. As described above, when the power supply voltage fluctuates, accurate measurement cannot be performed. For example, if the output signal is 0
For testing on ICs that vary from V to 3V, the target level must be modified to 1.5V. Also, in a test on an IC whose output signal is expected to change from 0V to 5V, in practice, when the output signal changes from 0.1V to 5.2V, if the target level is set to 2.5V,
Accurate measurement is no longer possible.

In the IC test apparatus according to the present invention, an accurate target level is automatically set. Hereinafter, the operation will be described. First, the operator sets the time setting means 4
1, the time point at which the input signal changes stepwise is referred to as a reference time t0.
, Predetermined times t1 and t2 are set. Here, time t1 is an arbitrary time that is expected to be in a period before the output signal still shows a change after the input signal is applied, and time t2 is a time when the output signal changes due to the input signal being applied. And any time at which the change is expected to be sufficiently stable. In other words, the change in the output signal at time t1 is expected to be 0%, and the change in the output signal at time t2 is expected to be 100%. Specifically, as shown in FIG. 2, the time t1 may be set immediately near the reference time t0, and the time t2 may be set at a position where a sufficient time has passed therefrom. Time t1 is sufficiently before the time when output signal B rises, and time t1
No. 2 is after the output signal B has completely risen. Further, the operator sets the change rate x of the output signal level which defines the transient response time T to be measured in the rate setting means 42. For example, to measure the transient response time T required for the change in the output signal level to reach 50%,
What is necessary is just to set the change ratio x = 50%. As described above, in this IC test apparatus, the operator operates at time t1,
It is only necessary to perform the work of setting t2 and the change rate x. Once these set values are set once, there is no need to change even if the voltage value of the input / output signal changes.

When the output signal B as shown in FIG. 2 is fetched from the output waveform fetching means 30, the target level calculating means 43 automatically calculates the target level by the following method. First, for the output waveform B, a level L1 at a set time t1 and a level L2 at a time t2 are obtained. In the example shown in FIG. 2, L1 = 0V,
L2 = 5V. The output levels L1 and L2
And the target level L is obtained by apportioning the change with the change rate x. That is, the target level L is obtained by the calculation of L = L1 + (L2-L1) .x. In the example shown in FIG. 2, a target level L = 2.5 V is obtained by apportioning between 0 V and 5 V at a change rate of 50%. When the target level L is obtained in this way, the transient response time calculating means 44
The output signal B is analyzed to determine the time t at which the voltage value becomes equal to the target level L, and the time from time t0 to time t is output as the transient response time T.

If the transient response time T is determined by such a method, no problem occurs regardless of the range of the voltage value of the output signal B. For example, when the output signal B has a range of 0V to 3V, L1 =
A measurement result of 0 V and L2 = 3 V is obtained, and the target level is an appropriate value of L = 1.5 V. Further, the output signal B is set to 0.1 V to 5.2 V due to a change in the power supply voltage or the like.
, L1 = 0.1V, L2 = 5.
A measurement result of 2 V was obtained, and the target level was L = 2.6.
This is an accurate value of 5V.

As described above, the output waveform capturing means 30
The output signal is digitized and input to the computer 40. Therefore, the calculation processing in the target level calculation means 43 and the transient response time calculation means 44 is performed based on the digitized data. Accordingly, the output signal B shown in FIG. 2 is defined only by discrete values sampled. Therefore, for example, when the voltage value L1 corresponding to the time t1 or the voltage value L2 corresponding to the time t2 is obtained, or when the time t corresponding to the target level L is obtained, a so-called binary search method may be used. Although this binary search method is a known technique, only its principle will be briefly described here.

Now, when a graph C showing the relationship between time and voltage value as shown in FIG. 3 is given, it is considered that a voltage value Vx corresponding to a predetermined time tx is obtained by a binary search method. . FIG. 4 shows a flowchart of a procedure for obtaining the voltage value Vx by the binary search method. First, as shown in FIG. 3, with a predetermined time tx as a boundary, one of the time axes is defined as a pass area and the other is defined as a fail area. Then, in step S1, the corresponding time t _P is set sufficiently voltage value V _P that is expected to will be present in the path region. Similarly, in step S2, the corresponding time t _F is sufficiently set the voltage value V _F that is expected to will be present in the fail region. Then, step S3
_In, the _{V M = (V P + V} F) / 2 becomes formula,
Seek an intermediate value _{V M.} In Figure 3, the intermediate value V _M obtained in this way, V _M1 in the sense that the first intermediate value
It is shown. Subsequently, in step S4, | V _P −
V M _| is, determines whether it is smaller than the predetermined resolution. If a negative determination is made here, step S
In 5, V _M is whether the path area is determined. In the example of FIG. 3, the time t _M1 corresponding to V _M1 can be judged to be in the path region. In this case, in step S6, the intermediate value _{V M} far as the new _{V P,} the flow returns to step S3. Conversely, when a fail-region, in step S7, an intermediate value V _M far as the new V _F, the process returns to step S3. After all, in the example of FIG. _3, the _{V M1} as a new _{V P,} so that the process returns to step S3. Then, in step S3, this _VM1
An intermediate value _{V M2} of the (new _{V P)} and _{V F} is determined, when the negative determination in step S4 is performed, step S5
In time t _M2 corresponding to V _M2 is whether the path area is determined. In the example of FIG. 3, since the time _{t M2} is in the fail region, in step S7, an intermediate value _{V M2} far as the new V _F, the process returns to step S3. Thus, the position of the V _P and V _F is sequentially updated, both intervals will come gradually narrowed. Finally, in step _{S4, |} V P -V _{M |} is, if it is determined to have become smaller than the predetermined resolution, the step S
In 8, a Vx determining the values of V _P at that time, the binary search method is completed. It should be noted that, when obtaining the time tx corresponding to the predetermined voltage value Vx, the binary search method can be used in the same procedure as described above.

As described above, the present invention has been described based on the illustrated embodiments. However, the present invention is not limited to only these embodiments, and can be implemented in various other modes. For example, in the above-described embodiment, a signal rising stepwise is used as an input signal, but a signal falling stepwise may be used. Alternatively, a signal that changes more slowly may be used. Further, in the above-described embodiment, an example in which the operation on the digital data is performed by the binary search method has been described, but the operation may be performed by another method.

[0017]

As described above, in the IC test apparatus according to the present invention, the target level calculating means automatically calculates the target level using the actually measured level values L1 and L2 of the output signal. Setting work is unnecessary,
An accurate transient response time T can be obtained with a simple operation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of an IC test apparatus according to the present invention.

FIG. 2 is a graph showing input signals and output signals used in the device shown in FIG.

FIG. 3 is a graph illustrating a binary search method performed by the apparatus shown in FIG. 1;

FIG. 4 is a flowchart showing a procedure of a binary search method performed by the apparatus shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... IC to be tested 20 ... Input signal generating means 30 ... Output waveform capturing means 40 ... Computer 41 ... Time setting means 42 ... Ratio setting means 43 ... Target level calculating means 44 ... Transient response time calculating means A ... Input signal B: output signal C: graph showing the relationship between time and voltage value T: transient response time

Continuation of the front page (56) References JP-A-3-138579 (JP, A) JP-A-2-247585 (JP, A) JP-A 64-7813 (JP, A) JP-A-61-117466 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01R 31/28 G01R 31/3183 G01R 31/319

Claims (1)

(57) [Claims] When a predetermined input signal is supplied to an IC to be tested, a transient response time T required until a change in an output signal level according to the input signal reaches a predetermined ratio is determined. An IC test apparatus for measuring, an input signal generating means for generating a predetermined input signal to be supplied to the IC, an output waveform capturing means for capturing a waveform of an output signal output from the IC, and a predetermined reference time t0 At the reference time t0.
Output signal still shows change when input signal is given
Any time t1 expected during the previous period and the input signal
Signal changes the output signal, and the change
Set an arbitrary time t2 expected to be stable in minutes.
Time setting means, a rate setting means for setting a change rate x of an output signal level that defines a transient response time to be measured, and a level L1 at the time t1 for an output waveform captured by the output waveform capturing means. , The level L2 at the time t2, and the output level L1 and L2 are proportionally divided by the change rate x to obtain the target level L. Transient response time calculating means for determining a time t at which the output level reaches the target level L and determining a time from the reference time t0 to the time t as a transient response time T to be measured. An IC test apparatus characterized by the above-mentioned.