JPH05308287A - Dynamic characteristic measurement device - Google Patents

Abstract

PURPOSE:To simply measure the dynamic characteristic of a D/A converter circuit at mass-production shipment measurement by inputting specific data to D/A converter circuit being an object of measurement and measuring its output. CONSTITUTION:A multiplexer 4 selects alternately sine data D1 and DC data D2 inputted from a sine wave ROM 2 and a DC data generating circuit 3 in a timing of a clock signal CK to apply time division multiplex and outputs the result as dynamic characteristic measurement digital data D3. A D/A converter circuit 5 converts the dynamic characteristic measurement digital data D3 into an analog signal and it is outputted as a high frequency analog signal S1. A low pass filter 6 eliminates the high frequency components from the high frequency analog signal S1 to extract an envelope component and outputs the envelope component as a low frequency signal S2. A spectrum analyzer 7 measures the S/N of the low frequency signal S2 to measure distortion caused in the signal waveform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic characteristic measuring device,
In particular, it is suitable for application to those that measure the operating characteristics of digital / analog conversion circuits.

[0002]

2. Description of the Related Art Conventionally, the maximum operating characteristics, settling measurement,
Although there are grit measurements and the like, methods for measuring these dynamic characteristics (that is, characteristics when the output analog signal frequency is high frequency) at the time of shipment have not been established yet, so static characteristics (that is, output analog signal frequency It is designed to measure only the characteristics when the frequency is low.

Therefore, for mass production shipment measurement, 1 [kh
z] The input signal with a signal frequency of about
It is input to an analog conversion circuit, and only DC measurement and output waveform linearity measurement are performed.

[0004]

However, even if no defect is found in the static characteristic measurement, the digital / analog conversion circuit must sequentially convert a digital signal having a signal frequency of 40 [MHz] into an analog signal. , It did not work properly when actually used.

The present invention has been made in consideration of the above points, and an object thereof is to propose a dynamic characteristic measuring apparatus capable of easily measuring the dynamic characteristic at the time of mass-production shipping measurement.

[0006]

In order to solve such a problem, according to the present invention, a first digital data output for outputting the first digital data D1 containing an AC component at a first frequency (1 [kHz]). Second means for outputting the second digital data D2 of a predetermined level (logic "0")
Digital data output means 3 of the second frequency (500
[MHz]), the first and second digital data D1
And D2 are time-division-multiplexed and output to the digital / analog conversion circuit 5 to drive the digital / analog conversion circuit 5 in the dynamic characteristic mode;
The analog conversion output S output from the analog conversion circuit 5
A low-pass filter 6 for inputting 1 and extracting a low-frequency component from the analog conversion output S1 and a low-pass filter 6
And a dynamic characteristic measuring means 7 for measuring the dynamic characteristic of the digital / analog conversion circuit 5 based on the extracted low frequency component.

[0007]

The first frequency (1 [kHz
z]) first digital data D1 and second digital data D2 of a predetermined level (logic "0") are multiplexed at a second frequency (500 [MHz]) and input to the digital / analog conversion circuit 5. By driving the digital / analog conversion circuit 5 in the dynamic characteristic mode, the low-frequency component is extracted from the analog conversion output S1 of the digital / analog conversion circuit 5 via the low-pass filter 6 to obtain the dynamic characteristic. Can be measured by a much simpler method than the conventional method.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an operating characteristic measuring device for a digital / analog converting circuit as a whole, which is adapted to measure the operating characteristic of an 8-bit digital / analog converting circuit.

Here, the dynamic characteristic measuring apparatus 1 uses the sign data generating ROM (read only memory) 2 and the DC data generating circuit 3 to output 8-bit sign data D1 and DC data D.
2 is supplied to the multiplexer 4.

Incidentally, the sine data D1 is a sine waveform obtained by reading the low frequency sine wave data of 1 [kHz] at the timing of the clock signal CK of 500 [MHz], and the DC data D2 is a logic "8" in all 8 bits. The digital data "0" is read at the timing of the clock signal CK of 500 [MHz].

At this time, the multiplexer 4 alternately switches and outputs the sine data D1 and the DC data D2 at the timing of the clock signal CK, so that the logic value is comb-shaped, that is, the logic value is the logic "0" level and the sine wave. The dynamic characteristic measurement digital data D3, which alternately switches the values on the envelope of, are output to the digital / analog conversion circuit 5 (FIG. 2).

Here, the digital / analog conversion circuit 5
Is 250 [MHz], which is 1/2 the clock frequency and has a high signal frequency and a large variation in the logical value. The dynamic characteristic measurement digital data D3 is sequentially converted into an analog signal at the timing of the clock signal CK (hereinafter, the dynamic characteristic mode). That is, the high-frequency analog signal S1 is output to the low-pass filter 6.

At this time, the low-pass filter 6 removes the high-frequency component from the high-frequency analog signal S1 to extract the envelope component of 1 [kHz], and outputs the envelope component to the low-frequency signal S2.
Is output to the spectrum analyzer 7 (FIG. 3).

Incidentally, in the high frequency analog signal S1, the same sign data D1 is repeated by several clocks as shown in FIG. 4A in which the signal waveform is enlarged, and the frequency of the envelope component of the high frequency analog signal S1 is small. It is made to become.

Here, the spectrum analyzer 7 measures the SN ratio of the low frequency signal S2 by operating the digital / analog conversion circuit 5 in the dynamic characteristic mode by the low pass filter 6 to measure the distortion generated in the signal waveform. The digital / analog conversion circuit 5, which is the object of measurement, determines whether or not it normally operates even in a high frequency band.

Incidentally, in the case of an 8-bit digital / analog conversion circuit, the SN ratio ideally takes a value of around 48 [dB], and is smaller than the value when the digital / analog conversion circuit is abnormal. I know that it takes a value.

In the above configuration, when the signal terminal for inputting / outputting the measurement signal and the input / output terminal of the digital / analog conversion circuit 5 to be measured are connected, the operation characteristic measuring apparatus 1 causes the multiplexer 4 to generate a sine wave. Sign data D1 input from the ROM 2 and the DC data generation circuit 3
And DC data D2 are alternately switched and supplied to the digital / analog conversion circuit 5 as dynamic characteristic measurement digital data D3.

Here, when the digital / analog conversion circuit 5 to be measured operates normally, the high frequency analog signal S output from the digital / analog conversion circuit 5 is output.
As shown in FIG. 4 (A), the enlarged waveform of No. 1 is a high-frequency waveform that rises to the right and regularly increases stepwise. As a result,
The output waveform of the low-pass filter 6 corresponding to the envelope of the high-frequency analog signal S1 becomes a straight line rising to the right when observed in a minute time, as shown in FIG.

On the other hand, when the internal decoder of the digital / analog conversion circuit 5 malfunctions and outputs a wrong analog signal (FIG. 5A) or when a grid occurs (FIG. 6A), a high frequency is generated. The signal amplitude of the analog signal S1 has a partially protruding value. As a result, the output waveform of the low-pass filter 6 corresponding to the envelope of the high-frequency analog signal S1 is distorted in a portion where a malfunction occurs when observed in a minute time as shown in FIG. 5 (B) and FIG. 6 (B). Occurs and the output waveform is integrated but becomes a waveform that deviates from the straight line.

As a result, the dynamic characteristic when the digital / analog conversion circuit 5 is driven by an input signal having a high frequency of 250 [MHz], which is one half of the clock frequency, and a large variation in the logical value, is as low as 1 [kHz]. It can be measured from the frequency envelope waveform, and the dynamic characteristics can be measured by a simple method.

According to the above configuration, the dynamic characteristic measurement digital data D3 for alternately switching the high frequency between the low frequency sine data D1 and the logic "0" DC data D2 is input to the digital / analog conversion circuit 5 to be measured. To operate in the dynamic characteristic mode, and measure the envelope waveform of the analog output through a low pass filter
The dynamic characteristics of the analog conversion circuit can be measured by a simple method.

In the above embodiment, 1 [kHz]
The low-frequency sine data D1 and the logic "0" DC data D2 are alternately switched by the multiplexer 4 at a high frequency of 250 [MHz] and supplied to the digital / analog conversion circuit. Not limited to this, the present invention can be widely applied to the case where the low frequency sine data of 1 [kHz] stored in the read-only memory is sampled at the sampling frequency of 250 [MHz].

Further, in the above-mentioned embodiment, the case where the sign data of 1 [kHz] is used as the low frequency signal has been described, but the present invention is not limited to this, and is widely applied to the case of using the sign data of other frequencies. Applicable.

Further, in the above-described embodiment, the low frequency sine data D1 and the DC data D2 of logic "0" are set to 500
Multiplexed at a high frequency of [MHz], 250 [MH
The case where the dynamic characteristic measurement digital data D3 of z] is output has been described.
The present invention can be widely applied to the case of multiplexing and outputting at another frequency such as [MHz].

Further, in the above-mentioned embodiment, the case where the sine data of the sine waveform is used as the low frequency signal has been described, but the present invention is not limited to this, and the signal whose logic value greatly changes when switched to the DC data D2. It can be widely applied when using a waveform.

Further, in the above-mentioned embodiment, the case where the logic level of the DC data D2 is set to the logic "0" has been described, but the present invention is not limited to this and is widely applied to the case of taking other logic levels. obtain.

[0028]

As described above, according to the present invention, the first digital data of the first frequency and the second digital data of the predetermined level are time-division multiplexed at the second frequency to perform digital / analog conversion. By inputting to the circuit, the digital / analog conversion circuit is operated in the dynamic characteristic mode, and the low frequency component of the analog conversion output is measured through the low-pass filter to easily measure the dynamic characteristic of the digital / analog conversion circuit. can do.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a dynamic characteristic measuring apparatus according to an example.

FIG. 2 is a schematic signal waveform diagram for explaining dynamic characteristic measurement digital data that is time-division multiplexed.

FIG. 3 is a signal waveform diagram showing a low-pass filter output during normal operation.

FIG. 4 is a schematic signal waveform diagram for explaining an analog output and its low-pass filter output during normal operation.

FIG. 5 is a schematic signal waveform diagram for explaining an analog output and its low-pass filter output when a malfunction occurs in the analog conversion.

FIG. 6 is a schematic signal waveform diagram for explaining an analog output and a low-pass filter output thereof when a grid is generated.

[Explanation of symbols]

1 ... Dynamic characteristic measuring device, 2 ... Sine wave ROM, 3 ...
DC data generation circuit, 4 ... Multiplexer, 5 ... Digital / analog conversion circuit, 6 ... Low-pass filter, 7 ... Spectrum analyzer.

Claims (2)

[Claims] 1. A first digital data output means for outputting a first digital data including an AC component at a first frequency, and a second digital data output means for outputting a second digital data of a predetermined level. , A multiplexing means for time-divisionally multiplexing the first and second digital data at a second frequency and outputting the time-division multiplexed digital data to a digital / analog conversion circuit, and driving the digital / analog conversion circuit in a dynamic characteristic mode; / A low-pass filter that inputs an analog conversion output output from the analog-conversion circuit and extracts a low-frequency component from the analog conversion output, and a digital-analog conversion circuit based on the low-frequency component extracted from the low-pass filter. A dynamic characteristic measuring device comprising: a dynamic characteristic measuring means for measuring a dynamic characteristic. 2. The dynamic characteristic measuring device according to claim 1, wherein the second frequency is higher than the first frequency.