JPH10142295A - Waveform measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of measurement of waveform by quantitizing the waveform itself of output signal from a device to be tested, storing it in a waveform memory, storing time-base data in a memory, storing a time-base measurement point as an event signal with the synchronization with the waveform memory, and performing arithmetic processing. SOLUTION: A waveform generated in an arbitral waveform generator 20 is supplied to a device to be tested 21, and the processed signal is given to a waveform digitizer 22 and a time digitizer 24. A clock generator 23 supplies clock signals CLK1, CLK2 to the generator 20 and the digitizers 22, 24. A CPU 25 controls the movement of command and data except for the device 21. The generator 20 stores the clock signal CLK1, and takes it out if necessary and give it to the device 21. To the digitizer 22 an output signal of the device 21 is input, then it is delayed with its high frequency components cut, and the clock signal CLK2 is stored as the event memory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform measuring apparatus for measuring and evaluating semiconductor devices such as LSIs, and more particularly to an automatic measuring device (tester).

[0002]

2. Description of the Related Art FIG. 8 shows a block diagram of a conventionally proposed waveform measuring apparatus. An output signal generated by the arbitrary waveform generator 10 according to a command from the CPU 14 is supplied to a test apparatus (D
The signal provided to the UT 11 and output from the EUT 11 is subjected to A / D conversion by a waveform digitizer 12 controlled by a CPU 14 and stored in a memory in the waveform digitizer 12. The clock generation circuit 13 is a circuit for generating a clock signal necessary for operating the arbitrary waveform generator 10 and the waveform digitizer 12 under the control of the CPU. That is, a digital signal necessary for operating the test device 11 is based on the clock signal CLK generated by the clock generation circuit 13.
0 and is supplied to the test apparatus 11.

[0003] Output data of the waveform digitizer is sent to a CPU, which performs necessary arithmetic processing and analysis.

As described above, in the conventional waveform measuring apparatus, generation of a waveform, analysis and storage of the waveform are performed by the clock generation circuit 1.
3, the synchronization and coherence (continuity) of the measurement system for realizing digital signal processing (DSP) are ensured.

[0005]

However, in such a conventional waveform measuring apparatus, measurement is performed using data taken in the waveform digitizer 12, and waveforms such as waveform level, phase, distortion and the like are measured. There is no problem when the same waveform is repeated at the same cycle because it only measures the analog characteristics of itself, but when the waveform changes with time, it is not enough to judge the quality of the output waveform.

For this reason, the following problems have been pointed out. (1) The resolution of the time axis is limited by the resolution of the clock pulse supplied to the waveform digitizer 12, and sufficient measurement accuracy cannot be obtained. (2) Since the information on the time axis is 12 address data by the clock pulse supplied to the waveform digitizer 12, the waveform processing is difficult to understand intuitively, and the processing itself becomes complicated.

The present invention has been made in view of the above problems, and has as its object to provide a waveform measuring apparatus having high measurement accuracy and easy waveform processing.

[0008]

According to the waveform measuring apparatus of the present invention, a reference clock generator for generating a reference clock, and a waveform generator for generating a test waveform to be supplied to a device under test based on the reference clock A waveform memory for quantizing and storing sampling points of an output waveform generated by the device under test from the test waveform, and a time for storing time axis data of points on the output waveform in synchronization with the sampling points An axis data memory, and an arithmetic unit that performs arithmetic processing based on the contents of the waveform memory and the time axis data memory to measure a waveform is provided.

In this device, the waveform itself of the output signal of the device under test is quantized and stored in a waveform memory, and at the same time, time-axis data is stored in a memory at a specified reference level, and a time-axis measurement point is set. A device for synchronizing with the above-mentioned waveform memory, storing as an event signal, and performing waveform measurement by arithmetic processing from these data, and used for an automatic measurement and evaluation device (tester) based on digital signal processing (DSP). .

[0010]

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

FIG. 1 is a block diagram showing a schematic configuration of a waveform measuring apparatus according to an embodiment of the present invention. According to FIG. 1, a waveform generated by an arbitrary waveform generator 20 is used as a test apparatus ( DUT) 21 and an output signal as a processing result in the test apparatus 21 is supplied to a waveform digitizer 22 and a time digitizer 24, and the processing described later is performed. The clock generation circuit 23 supplies a clock signal CLK to the arbitrary waveform generator 20, the waveform digitizer 22, and the time digitizer 24. Further, the CPU 25 is connected to each part except the DUT by a bus, gives a command for operating these parts, and manages data movement.

FIG. 2 is a block diagram showing a detailed configuration of the clock generator 23. The reference clock generated by the reference clock generator 231 is subjected to digital signal processing (D) by the frequency dividers 232 and 233 under the control of the control circuit 236.
SP) is divided to a possible division ratio, and the control circuit 2
36, an arbitrary waveform generator 20 and a waveform digitizer 22 via a start / stop circuit 235 controlled by
Are transmitted as clock signals CLK1 and CLK2.
As described later, CLK1 is a waveform memory clock, and CLK2 is a waveform data memory clock. The output of the reference clock generator 231 is also provided to the time measuring device 234, and the time data TM measured by the control of the control circuit 236 is also provided to the time digitizer 24 via the start / stop circuit 235. I have.

FIG. 3 is a block diagram showing a detailed configuration of the arbitrary waveform generator 20. This arbitrary waveform generator 20 has a CP
A waveform memory 201 controlled by a control circuit 204 controlled by U, a DA converter 202, and a low-pass filter 203 are provided.

The low-pass filter 203 used here is a reconstruction filter.

The waveform memory 201 stores the clock signal CLK1 output from the clock generator 23. The stored contents are taken out as necessary, converted into an analog signal by a DA converter, and the high-frequency component is cut by a low-pass filter and supplied to a test device.

FIG. 4 is a block diagram showing details of the waveform digitizer 22. This waveform digitizer 22 delays the input output signal of the EUT by a delay circuit 221, cuts a high frequency component through a low-pass filter 222, and
It has a waveform data memory 224 for storing a waveform in response to a clock signal CLK2 of a clock generator after converting the signal into a digital signal by a D converter 223, and an event memory 225 for storing an event based on an output of a time digitizer.

It is preferable that the low-pass filter 222 used here is an anti-alias filter that passes only a half or less of the sampling frequency.

The delay circuit 221 is for adjusting the timing of the waveform data memory 224 and the event memory 225 on the time axis.

FIG. 5 is a block diagram showing details of the time digitizer 24.

The time digitizer 24 is supplied with the time data TM output from the clock generator 23, and the output signal from the EUT is supplied to the time axis data memory 244 via the delay circuit 241 and the comparator 242 and stored therein. You. The comparator 242 is a control circuit 24
5. Compare the trigger level (threshold reference level) generated from the trigger level generator 243 controlled by 5 with the output signal of the EUT, and generate a comparison output when the level of this output signal is higher than the trigger level. Then, this comparison output is supplied to the time axis data memory 244 as a time axis data write signal, and time data representing the real time on the time axis is stored in the time axis data memory 244.

It is an important event that the output of the EUT exceeds the threshold reference level.
The time axis measurement point is sent as event information to the waveform digitizer 22 and stored in the event memory.

The delay circuit 243 is for adjusting the timings of the event memory 225 and the time axis data memory 244 on the time axis.

FIG. 6 is a waveform diagram showing how the waveform is recorded, and FIG. 7 is an explanatory diagram showing the state of the memory in which the waveform shown in FIG. 6 is recorded.

FIG. 6 shows a reference clock output from the reference clock generator 231 and a waveform data memory 2 based on the reference clock.
4 shows a clock CLK2 supplied to 24, an output waveform of the EUT, and a waveform recorded in a waveform data memory. As described above, the waveform and time are determined by the reference clocks CLK1 and CLK2 output from the clock generator.
And the time signal TM. Therefore, the resolution of these stored data is the time resolution of the reference clock generator 231.

D1, d2,... Di,.
6 shows the data taken into the waveform data memory 224 of the waveform digitizer 22. As is clear from the waveform of FIG. 6, the output waveform from the EUT 21 is quantized and stored. The event memory 225 has
Event information represented by “0” or “1” is stored in synchronization with the waveform data memory 224. As described above, this event information is stored by a signal that the comparator 242 included in the time digitizer 24 detects that the reference level has been exceeded.

.. Ti,... Tn in FIG.
Is the data fetched into the time axis data memory 244. This data indicates that the output waveform of the EUT has exceeded the preset trigger level.
It is a timing signal generated when detected by 42, and is stored as time data TM output from the clock generator 23.

The CPU 25 can exchange data with the arbitrary waveform generator 20, the waveform digitizer 22, the clock generator 23, and the time digitizer 24 via a bus.
24, event memory 225, time axis data memory 24
4. Data can be extracted from the data No. 4 and necessary measurement values can be calculated by arithmetic processing.

For example, for the waveform in the section A, parameters such as level and distortion can be obtained by DSP processing from the data d6 to di in the waveform data memory 224.
In addition, the section A can be easily specified by the contents stored in the event memory 225. On the other hand, the frequency can be accurately obtained from the data t1 and t2 in the time axis data memory 244.

In the example of FIG. 6, the period of the output waveform changes in each of the sections A, B, and C. Such a change can be easily detected by monitoring the interval between the points when the trigger level is exceeded. Can be detected.

In general, analog signals input to and output from the EUT 21 often require high-resolution time-axis data such as transient response characteristics. In order to satisfy this requirement, the frequency generated by the reference clock generator 231 may be increased, and the frequency division ratio of the frequency dividers 232 and 233 may be increased.

In the above embodiment, the sampling of the waveform is performed at a constant timing for each cycle of the repetitive waveform. However, the sampling point (timing) may be slightly shifted for each cycle. good.

[0032]

As described above, according to the present invention, not only waveform data but also time is recorded, so that accurate measurement can be performed even when the waveform itself changes with time. Moreover, the processing of the extracted waveform is facilitated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a waveform measuring device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of an arbitrary waveform generator in FIG. 1;

FIG. 3 is a block diagram showing a detailed configuration of a waveform digitizer in FIG. 1;

FIG. 4 is a block diagram showing a detailed configuration of a clock generator in FIG. 1;

FIG. 5 is a block diagram showing a detailed configuration of a time digitizer in FIG. 1;

FIG. 6 is a waveform chart showing an operation of the waveform measuring device according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a state of storing waveform data and the like in the waveform measuring device according to the embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a conventional waveform measuring device.

[Explanation of symbols]

 Reference Signs List 20 arbitrary waveform generator 21 EUT 22 waveform digitizer 23 clock generator 24 time digitizer 25 CPU 201 waveform memory 202 D / A converter 203 low-pass filter 204 control circuit 221 delay circuit 222 low-pass filter 223 A / D converter 224 waveform data memory 225 Event memory 226 Control circuit 231 Reference clock generator 232, 233 Divider 234 Time measuring device 235 Start / stop circuit 236 Control circuit 241 Delay circuit 242 Comparator 243 Trigger level generator 244 Time axis data memory 245 Control circuit

Claims (4)

[Claims] A reference clock generator for generating a reference clock; a waveform generator for generating a test waveform to be supplied to a device under test based on the reference clock; and a waveform generator generated from the test waveform by the device under test. A waveform memory for quantizing and storing sampling points of the output waveform; a time axis data memory for storing time axis data of points on the output waveform in synchronization with the sampling points; a waveform memory and the time axis data memory And a calculation unit for performing a waveform measurement by performing a calculation process based on the contents of the above. 2. The waveform measuring apparatus according to claim 1, further comprising an event storage means for storing, as an event, a trigger signal given when measuring the time axis. 3. A comparator for comparing the output waveform with a reference level for storing time axis data, and outputting the trigger signal when the level of the output waveform is higher than the reference level. The waveform measuring device according to claim 2, wherein: 4. The waveform measuring apparatus according to claim 1, wherein said waveform generator creates said test waveform based on a signal obtained by dividing said reference clock.