SU1287285A1 - Device for checking analog-to-digital converters - Google Patents

Abstract

The invention relates to a measurement technique and is intended for the integral and differential static characteristics of analog-to-digital converters. The evaluation of the characteristic values is carried out by the average value of the real transform threshold levels, which makes it possible to determine the quantization step and the differential HPP nonlinearity of the transform characteristic. The invention improves the measurement accuracy of parameters and determines the measurement error of the average level of the converted voltage from the output of the measurement signal generator 1 by a digital voltmeter 2. The generator is controlled by the measurement signal generator control unit 7, the reference code generated by the reference code generator 5 is compared in digital comparator 4 with the code of the checked analog-digital converter 3 according to the results of comparison, the signals from the output of the digital comparator are es OR element 8 and reversible counter 9 is controlled by unit 7 and the control unit 10 a digital voltmeter. CSP. f-ly, 6 ill. with S9 (L

Description

The invention relates to an experimental technique and can be used to test analog-to-digital converters.

The purpose of the invention is to expand the field of application by making it possible to measure the static characteristic by average values of real threshold levels,

Figure 1 shows the structural diagram of the meter static characteristics of the ADC; figure 2 - the timing diagram of the meter; on fig.Z - 6 schematic diagrams (synna second input of digital comparator 4 with shaper 5 of reference code.

To install the blocks and elements of the device to the initial position and start the process of automatic measurement of the static characteristic of the tested A / D converter, a signal to start the measurement process is sent to the input of the device (if

ment t on figa).

In synchronizer 6, an internal waiting clock generator is started, from which start-up pulses of the tested

generator, control unit of the generator-ADC (Fig.26), the signal of the initial meter of the measuring signal, the block of the block 7 of the control generator of the digital voltmeter control, the measuring signal into the initial juice of the control of the state measuring cycles, the synchronization pulses of the digital comparator 4 and block 12 pack; measurement cycles.

At the initial installation signal

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responsibly.

The device contains a measuring signal generator 1, a digital voltmeter 2, a test digital analog converter 3, a digital comparator 4, a reference generator 5. code, synchronizer 6, measurement signal generator block 7, element OR 8, reversible counter 9, control block 10

digital voltmeter, block 11 register-. „". „„, „

radio, block 12 control cycles from the generator 1 measuring measurement signal, causes the formation of the unit control unit 7 generator of the last measurement signal U (measurement signal is performed on the element OR-NOT 13, trigger 14, register 15 shift. The device also contains a block of 16.

The digital voltmeter control unit 10 is implemented on two elements OR-NOT 17 and 18 and trigger 19.

unit 7, taken from the output of the synchronizer, unit 7 is set to the initial state and begins to generate a control signal for the measuring signal generator Uu (Fig. 2a).

The control signal U, depending on its magnitude and sign, affects (Fig. 1o |), which is a linearly increasing or linearly decreasing voltage, depending on the sign of the control signal UN. Speed

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the change in the measurement signal Uj is determined by the magnitude of the control signal Uy.

The measurement cycle control unit 12 is implemented on an SHSh 20 element, an ifepe 21, an IS-NOT element 22, a divider 23, a decoder 24.

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to the second input of the digital comparator 4 with the imager 5 of the reference code.

To install the blocks and elements of the device to the initial position and start the process of automatic measurement of the static characteristic of the tested A / D converter, a signal to start the measurement process is sent to the input of the device (if

ment t on figa).

In synchronizer 6, an internal waiting clock generator is started, from which start-up pulses of the tested

five

. „„. „„, „

on generator 1 of the measuring signal, causes the formation of the posblock 7, taken from the synchronizer output, block 7 is set to the initial state and begins to generate a control signal for the generator of the measuring signal Uu (Fig. 2a).

The control signal U, depending on its size and sign, influences the measurement signal U (

(fig.1o |), which is a linearly increasing or linearly decreasing voltage depending on the sign of the control signal UN. Speed

the change in the measurement signal Uj is determined by the magnitude of the control signal Uy.

In the initial state, the control block 7 generates a signal for the control of the IC, the magnitude and sign of which cause the generator to form

The device is an automatic check of the solid signal U, corresponding to the analog-digital converter to one of the extreme values of

works as follows. Input signal voltage (either maximum or minimum), the generator output signal 1 of the measuring characteristic of the tested signal is removed, measuring 50 A. CP (time t in fig. 2a) Fig, signal 2a and q (Fig. 2a) and the input illustrates the measurement process of the digital voltmeter 2 and the input of the tested analog-digital converter (ADC) 3. The latter converts the current value of the measurement signal 55 into the corresponding code A,

tic characteristics with an increase, the measuring signal from the minimum value to the maximum.

Further, in the process of measuring the static characteristic, to generate the necessary control signal Uu, the control of unit 7 is carried out

which is fed to the first input of the digital comparator 4 to compare it with the reference code B supplied

the characteristic of the tested A.CP (moment t in fig. 2a). Fig. 2a illustrates the process of measuring the

tic characteristics with an increase, the measuring signal from the minimum value to the maximum.

the characteristic of the tested A.CP (moment t in fig. 2a). Fig. 2a illustrates the process of measuring the

Further, in the process of measuring the static characteristic, to generate the necessary control signal Uu, the control of unit 7 is carried out

signals arriving at its inputs from a reversible. counter 9.

The measuring signal generated by the measuring signal generator 1 and (Fig. 2a) is fed to the input of the ADC being tested, dp converting its value to the corresponding code value (code A) and to the input of the digital voltmeter 2 to measure the value of the measuring signal.

As the measuring signal generator 1, a linear voltage generator is used, the measurement rate of the voltage at the output of which is determined by the voltage value of the control signal Uy, and the direction of measurement by the sign of the control signal Uy.

It is possible as a measuring signal generator 1 to use a controlled digital-to-analog converter (PAP), to the positive and negative control inputs of which, in this case, it is necessary to give control signal Uy in the form of a pulse train in block 7.

When entering from the synchronizer 6 to the tested ADC 3 trigger pulses of the ADC (FIG. 2), the converter 3 generates code A, corresponding to the current value of the measuring signal Uj (shown in Fig. For example, code A is equal to). The generated code A is fed to a digital comparator A, at the same time to the second input of which from the driver: 5 of the reference code the reference code B is fed (FIG. 2E). According to the signal of the beginning of the measurement process, code B is supplied from the generator of the reference code, the value of which corresponds to the minimum code value of the static characteristic of the tested ATP (in the example shown in Fig. 2 & code B equals A i).

Digital comparator 4 is designed with a frequency of starting A1 signals of the ratio of codes A and B. As a result of comparison of codes in the process of measuring the static characteristic, digital comparator 4: produces 3 types of signals: either Code B or Code A

or code A from code B.

AT

at the beginning of the process of measuring the value of the control signals Uu, the measuring signal U and the code. And must necessarily provide you

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35 0 5

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Completion condition code A code B (fig.3q). At the same time from the digital comparator 4 to the first input of the reversible counter 9 receives a signal Code A of the code in (FIG. 2; k). After filling the reversing counter 9 via the channel Code A: code B, an overflow pulse is generated at its first output (Fig. 2i), which is fed to the first input of block 7, or to confirm the previously occurring sign of the control signal Uy (as shown at position 1 in fig. 2i) ,, or dp of measuring the sign of the control signal U (. (at position 2 in fig. 2c). In the signal interaction shown in figure 2, the positive sign of the signal, control Uq (figure 2) causes linear - the increasing change of the measuring signal i (fig.2o |), while checking The ADC generates A code, corresponding to the value.

As the measuring signal of the PC increases to the value corresponding to and higher than the average i value of the threshold level of the ADC, the converter under test begins to generate a code A equal to. When comparing in digital comparator 4 the value of code A with the value of code B equal to, digital comparator 4 stops producing a signal Code A code B (FIG. 2g) and starts generating a code in Code (FIG. 2), which: from its first output B is supplied to the element OR 8 and further to the second input of the reversible counter 9. After the reversing counter 9 is filled through the channel code, an overflow pulse is generated at its second output, code B (FIG. 2k), which is fed to the second input of block 7 to change the sign of the control signal and and (fig.2d). A change in the sign of the control signal Uh leads to a change in the direction of change in the measuring signal Uj, generated by the generator 1.

; Simultaneously with this procedure, the overflow pulse of the reversible counter 9 Code B (Fig. 2k) is fed to the second input of the unit 10 to start it. Block 10 is designed to form a digital voltmeter trigger pulse (Fig. 22) at the time the first of the overflow pulses arrives at the input of block 10.

second output of the reversing counter 9.

A trigger pulse of a digital voltmeter, generated by block 0, is applied to the first auxiliary input of a digital voltmeter 2 for switching it to measurement mode. Digital voltmeter 2 is designed to measure the average value of the voltage of the measuring signal U at its input from the measuring signal generator, to generate a digital code () corresponding to the measured average value of the measuring signal, as well as to generate a signal of the end of the measurement process (Fig. 2e ). The digital code from the first output of the digital voltmeter 2 is fed to the first input of the registration unit 11 for storing and displaying it.

The measurement time () of the measurement signal is determined by the type of digital voltmeter. At the end of the measurement process, a digital voltmeter 2 generates a signal for the end of the measurement process (Fig. 2e).

The signal for the end of the measurement process generated at the second output of the digital voltmeter 2 is fed to the second input of the unit 10 and to the first input of the measurement cycle control unit 12.

Block 10 is set to its initial state, i.e. The first pulse in time (position 1 in Fig. 2k) from the sequence of overflow pulses (Fig.) taken from the second output of the reversing counter 9 goes to the standby mode. With PSx: this pulse blunt, unit 10 restarts the digital voltmeter 2 into measurement mode.

Signal end of measurement process W

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The registration unit 1 1 converts binary information into a decimal one and, according to the signal from block 12, generates information for display by an external recording device. Simultaneously with the information on the average value of the measurement signal, the registration unit 11 generates for recording the signal of the operation cycle number, the value of code B, as well as any other information that can be obtained from the values of the average values of the threshold level of the static characteristic of the converter. .

The formation of the measuring signal Uj, for measuring the average value, i is the threshold level of the checked ACCH1; 3 - occurs as follows.

After the start signal of the measurement process is input to the device, a linear increase in the value of the measurement signal occurs. When the device generates a trigger pulse of a digital voltmeter (Fig. 2d) and an overflow pulse of a reversible counter. 9 through channel Code B. (Fig. 2k), due to a change in the sign of the control signal Uu (Fig. 2e), the direction of change of the measuring signal Uy changes (Fig. 2oO). Further, with the current value of the measuring signal exceeding i, the threshold level is The ADC converter continues to generate a code equal to the reference code provided by the shaper of the reference code 5 from the beginning of the measurement process.

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thirty

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With a decrease in the measuring signal to the value of i - the threshold level AChch11- and below, the tested A / D converts the code A, equal to A B

The second (Fig. 2e), coming from the digital 45 comparison comparison code A of the second voltmeter 2 to the first input with the block reference code B A ij at digit 12, stimulates the output of the latter by the block 4 of the comparator 4, signals: the start signal blocks the formation of the signal of the registration code ka 11 taken from the first nerve by the output of the comparator output of block 12 and the signal measured 50 and begins to give a signal that the code b is not sent to the unit coming in the third exit (fig.2zh). The signal from the third output of the digital comparator 4 in the form of a pulse sequence, accessed at the first input of the reversible counter 9, overflows it through the channel of the code A - code B.

As a result, the reversive counter 9 at the first output generates the second output of the block 12 to the first additional input of the block 5 forming the reference code.

The registration unit 11 is designed to record measurement results obtained by a digital voltmeter.

2 as a binary digital code.

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The registration unit 1 1 converts binary information into a decimal one and, according to the signal from block 12, generates information for display by an external recording device. Simultaneously with the information on the average value of the measurement signal, the registration unit 11 generates for recording the signal of the operation cycle number, the value of code B, as well as any other information that can be obtained from the values of the average values of the threshold level of the static characteristic of the converter. .

The formation of the measuring signal Uj, for measuring the average value, i is the threshold level of the checked ACCH1; 3 - occurs as follows.

After the start signal of the measurement process is input to the device, a linear increase in the value of the measurement signal occurs. When the device generates a trigger pulse of a digital voltmeter (Fig. 2d) and an overflow pulse of a reversible counter. 9 through channel Code B. (Fig. 2k), due to a change in the sign of the control signal Uu (Fig. 2e), the direction of change of the measuring signal Uy changes (Fig. 2oO). Further, with the current value of the measuring signal exceeding i, the threshold level is The ADC converter continues to generate a code equal to the reference code provided by the shaper of the reference code 5 from the beginning of the measurement process.

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g pulse overflow (Figs. 2i, position 2), which, arriving at the first input of control unit 7, changes the sign of the control signal Un at its output (Fig. 22).

A change in the sign of the control signal and „causes a change in

jj leads to a change in the direction of increasing the direction of change of the measuring signal (Fig. 2a). At the same time, the tested ADC continues to generate a code. When the measurement signal reaches the value of the i - threshold level - and when it is raised, the ADC under test begins to generate code A.

Further, the process of changing the voltage of the measuring signal U, continues according to a sawtooth law, around the average value of i, the threshold level of the ADC, until the measurement of this voltage is completed by the digital voltmeter 2. During the measurement time of the measuring signal, the digital component of the measuring voltmeter the signal is formed and the value of the average level of the measuring signal corresponding to i is the average value of the threshold level of the ADC under test.

At the end of the measurement process, the i - threshold level - digital voltmeter 2 generates a signal. ending the measurement process (Fig.2o1), arriving at the first input of the measurement cycle control unit 12, By this signal, the signal unit 12 is removed from the first output, the recording unit 11 starts up, and the signal is removed from the second output, the code B changes in the driver 5 reference code per unit.

Thus, the operation is performed to register the mean i - known either A i or A i - 1, then code B exceeds code A.

From this moment on, the digital comparator 4 stops outputting the first 5 output to the first input of the element OR signal Code B (FIG. 2) and initiates the formation at the third output of the signal Code A code B, which is fed to the first input of the reversible 40 counter 9 After the channel is full, the code A of the code in the reversing counter 9 at its first output forms an overflow pulse (Fig.2i, in position 3), which through the second t5 input block 7 controls the measurement signal generator generates the control Uy with the sign providing at the output of the generator The measurement of the measuring signal into stop 20 by its increase. At the same time, the tested ADC generates code A, which corresponds to the area of formation of code A ACi-lO, and further as it grows, and code A.

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As the measurement signal rises to i + 1 - the threshold level of the ADC under test, the 3 rd above converter begins to generate code ZCOA + 1, when compared with the reference code B + 1J, digital comparator 4 stops generating the code A code B of the third output (FIG. .2) and start to give on the first output to the pen, the output input of the element 8 OR the signal Code A code B (Fig.2a). The latter, connected to the second input of the reversible counter 9, overflows it, as a result of which the overflow signal is generated at the second output of the counter (Fig. 2k, position 1). For the newly generated overflow signal, block 7 changes the sign of the control signal

the threshold level of the ADC and other (45 (Figure 2) and thus the direction

additional relevant information, as well as the transition to the measurement process (i + 1) - the average value of the threshold level of the ADC under test.

To perform the transition procedure in the driver of the reference code 5, the value of code B is changed by one, and the code B A i + 1 is applied to the second input of the digital comparator 4 from the driver 5 (FIG. 2K). Since the ADC being tested at this moment lends the formation of code A, equal to

87285 8

either A i or A i - 1, then code B exceeds code A.

From this point on, digital comparator 4 stops outputting the first B signal to the first input of an element of the OR 8 signal of the Code B (Fig. 2) and starts generating the A code B code on the third output of the signal, which is fed to the first input of the reversing 40 counter 9. After channel overflow Code A code in the reversible counter 9 at its first output generates an overflow pulse (Fig.2i, position 3), through which the measurement signal generator control unit Uy with the sign providing the generator output through the second t5 input block 7 controls the measurement signal generator Ator a change in the measuring signal in the direction of its increase. At the same time, the tested ADC generates code A, corresponding to the area of formation of code A ACi-lO, and further as it grows, and code A.

25

As the measurement signal increases to i + 1 - the threshold level of the ADC under test, the 3 rd above converter begins to generate code ZCOA + 1, when compared with the reference code B + 1J, digital comparator 4 stops generating the code A code B of the third output (FIG. 2) and start to give on the first output to the first, the first input of the element 8 OR the signal Code A code B (Fig.2a). The latter, entering the second input of the reversible counter 9, overflows it, as a result of which the overflow signal is generated at the second output of the counter (Fig. 2k, position 1). With the newly generated overflow signal, block 7 changes the sign of the control signal

changes in the measuring signal, and block 10 generates a pulse of starting a digital voltmeter (Fig. 2d) by which digital voltmeter 2 begins JQ to measure the value of the measuring signal Uy |.

Further, the operation of the device is repeated as described for measurement 55, i is the average value of the threshold level of the ADC under test.

Essential in the operation of the device is the selection of the values of the capacity of the reversible counter 9.

The choice of the capacity of the reversible counter 9 is determined by the following provisions. In practice, the value of the threshold level of real ADCs is random from one converter to another. The law of distribution of the threshold level values

A1SC is usually close to normal.

The introduction into the device of the reversible counter 9 is caused by the need to ensure the elimination of the influence of the random component of the current value of the threshold level on the accuracy of the measurement of its average value. For this purpose, with the help of a reversible counter 9, the measuring signal Uy, in the course of the measurement, is formed in the form of a sawtooth voltage with an amplitude of oscillation that is 3-4 times greater than the a priori known rms. value of the law of distribution of the threshold level (b).

The result of this requirement is

reversible counter is determined from the condition

3

m

t, dUn 5G

Where

at

- rms value of the threshold level distribution, determined by the accuracy requirement of the converter;

- ADC start-up period;

the rate of change of the measuring signal. With a measurement time of 1 (Fig. 2e), determined by the type of digital integrating voltmeter selected, the minimum rate of change of the measuring signal should be selected from the condition

.

T

"With 100 the repetition period of the measuring signal in the measurement process (Fig. 2a):

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dUH dit

at the same time we have

dUn, 12006 dt - The maximum permissible limit of the rate of change of the measuring signal is determined from the requirement

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28728510

whether the amplitude of the measuring signal is greater than the quantum value (h) of the static characteristic of the ADC under test, i.e.

aul,

5t t, M

If, for example, in the process of measuring i - the average value of the threshold level, a situation arises in which code A takes a value that exceeds the code B, then in order to save the process of automatic measurement of the average value i - threshold, the digital comparator 4 stops you25

the dacha at the first output of the code in and generates at the second output the signal of the code A-code B. The signal of the code A of the code B., entering the second input of the element 8 OR, and then acting properly on the block 7, enters pro; The measurement process is as described previously. At the same time, the signal Code A of code B can be used to register a code skip event in the ADC under test.

With proper choice of parameters

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Measuring the static characteristic of the tested ADC by the proposed device is determined only by the accuracy of measuring the average value of the alternating voltage (measurement signal and) by a digital voltmeter 2.

Claims (4)

Invention Formula I. An analog-to-digital transducer control device containing a measuring signal generator, the output of which is connected to the first input of a digital voltmeter and is the first output of the device, a digital comparator, the first input of which is connected to the output of the reference code generator, the second input is the input bus , the third input is connected to the 1C by the first output of the synchronizer, the input of which is combined with the first input of the reference code generator. And is the Start thickness, the second output of the synchronizer is the second output of the device The third output is connected to the first input of the control unit of the measuring signal generator, whose outputs are connected to the inputs of the measuring signal generator, which is In order to expand the field of application, an OR element, a reversible counter, a digital voltmeter control unit, a recording unit, a measurement cycle control unit, the first input of which is a Start bus, the second input is combined with the first input of the digital voltmeter control unit and connected to the digital output input. a voltmeter, the second input of which is connected to the output of the digital voltmeter control unit, and the output to the first input of the registration unit, the second inputs of which are connected to the first outputs of the cycle control unit the measurements, the third inputs of which are connected to the fourth outputs of the synchronizer, and the second output to the second input of the reference code generator, the first and second outputs of the digital comparator are connected to the first and second inputs of the OR element, respectively, whose output is connected to the first input of the reversible counter, the second input connected to the third output of the digital comparator, the first output to the second inputs of the digital voltmeter control unit and the measuring signal generator control unit, and the second output to the third im input of the control unit of the measuring signal generator. 2. The device according to claim 1, of which is that the control unit — Lenin's measuring signal generator — is implemented on the decoupling element of the shift register, the trigger and the IPI-NE element, whose input is the first block input, and the output is connected to the first input of the shift register, the second 10 f5 20 g 30 35 40 the inputs of which are connected to the outputs of the trigger, respectively, the first and second inputs of which are the second and third inputs of the block, respectively, the outputs of which are the outputs of the junction, the inputs of which are connected to the corresponding outputs of the shift register. 3. The device according to Claim 1, which is based on the fact that the digital voltmeter control unit is mounted on two OR-NOT elements and a trigger, the output of which is the output of the unit, the first and second inputs of which are the inputs of the first and of the second element OR NOT, respectively, the outputs of which are connected to the corresponding inputs of the trigger. 4. The device according to claim 1, that is, and that it is such that the control unit for measuring cycles is executed on the OR element, the trigger, the element. NAND, frequency divider, decoder, the first outputs of which are the first outputs of the block, the second output is connected to the first input of the NAND element, the second input of which, the first inputs of the decoder and the installation input to 1 trigger, the first the input of the device is the input of the setup to the flip-flop, the output of the rotor is connected to the first input of the OR element, the second input of which is the second input of the unit, and the output is connected to the first input of the frequency divider and is the second output of the unit, the second delhi entrance I ate connected to the output of AND-NO element and outputs connected to respective second inputs of the decoder. to - V . M (tt 5j 6 55 er, 5, Se P Tpuztep m / s 533 LAZ CusHojj free process of measurement Mjc 53ShZ generator Healer on Sfijc 2 W 23 M1c533LAZ, 5TN5-dB Signal on. valuable us- J. this novfa from block 6 Reversible counter signal (block 3) one. , Start ups - Dilator at 6 m / s 13THE5 k t§ | § 1, $ 141 t Nmpilbs - siihoonazatsii qi (gold $ th comparator The signal of the installation of the unit t / npbsleep by the generator of the measuring signal Startup impulses pro8er emovo ADC Fi.Z Measurement signal control signal