SU1690194A1 - Method of testing the bipolar digital-analog converters - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the static parameters of a D / A conversion. In order to increase the accuracy of the indication of the symmetry of the output voltages of the bipolar DAC, the following sequence of operations is provided. The digital inputs of the DAC are periodically supplied with codes that ensure the formation of bipolar pulses of positive, zero and negative amplitudes at the output of the DAC. From this sequence of pulses, the harmonic component is extracted and amplified with a period equal to half the period of change in the output voltage of the DAC. The amplitude of the selected harmonic is only zero when the perfect symmetry of the output voltages of the bipolar DAC is ensured, which ensures an increase in the accuracy of the symmetry indication. 2 Il. yo

Description

The invention relates to measurement technology and can be used to measure the static conversion parameters of digital-to-analog converters (D / A converters).

The purpose of the invention is to improve the accuracy of control of bipolar DACs.

Figure 1 shows the functional diagram of the device that implements the method; figure 2 - timing diagrams.

A device for monitoring bipolar DACs contains a pulse generator 1 connected in series, a counter 2, a multiplexer 3 connected to the target DAC 4, a filter 5, an amplifier 6, an indicator 7, as well as blocks 8-10 of setting the codes connected to the corresponding information inputs of the multiplexer 3 .

The method is carried out as follows.

Periodic codes are applied to the digital inputs of the digital-to-analog converter that ensure the formation of bipolar pulses at the output of the digital-to-analog converter. From this sequence of pulses, the harmonic component is extracted and amplified with a period equal to half the period of change in the output voltage of the DAC. The amplitude of the selected harmonic is only zero when the ideal symmetry of the output voltages of the bipolar DAC is ensured, which ensures an increase in the accuracy of the symmetry indication.

The device works as follows. The generator 1 generates a sequence of pulses and outputs it to the counter 2, the outputs of which are connected to the control inputs of the multiplexer 3, thereby connecting the output of the latter alternately to the outputs of the code setting blocks, respectively

oh oh

Yu

8-10. At the output of block 8, a code is set that corresponds to the checked voltage of the DAC of one polarity; at the output of block 10, the code corresponding to the voltage to be tested at the output of the DAC is of the same magnitude but of opposite polarity. At the outputs of block 9, a code is generated that corresponds to a zero voltage at the output of the DAC.

As a result of such transformations, a periodic sequence of positive and negative pulses is formed at the output of the DAC 4 with amplitudes equal to U + and U-, respectively, and a follow-up period equal to 4Т (Fig. 2), where T is the period of the pulse of the generator 1.

The harmonic component of this voltage is 1 / 2T:

+

+ aS2

T

(D

Where

AC2

one

2T

/ U-f cos (27Tt / 2T) dt +

4T

4T

4T

/ U-cos (27Tt / 2TJdt

ABOUT,

st

(2)

aS2

J

4 4T

2T

/ U + sln (2jrt / 2T) dt +

+ -zV / U-sin (27rt / 2T) dt4T

(3)

ST

-JJ ± L + Jb2 l -ru ++ U h 2TlLi + U

From the analysis of expressions (1-3), it follows that the output voltage of the DAC 4 contains a harmonic component with a frequency of 1 / 2T, and the value of this component is equal to the difference of the absolute values of the positive and negative voltages at the output of the DAC. This component is selected by frequency-selective filter 5, tuned to the frequency 1 / 2T, and the signal through the amplifier 6 is fed to the indicator 7.

Thus, a harmonic signal is applied to the input of the indicator, the amplitude of which carries information about the asymmetry of the positive and negative voltages at the output of the bipolar DAC. In the general case, the error in indicating the asymmetry value is determined by the instability of the transmission coefficients of the filter 5 and amplifier 6, but in any case, i.e. at any of their instability, the amplitude of the error signal at the output of amplifier 6 is zero with full symmetry

positive and negative voltages at the output of the DAC, which can be used to indicate the symmetry of these voltages with a high degree of resolving power.

Thus, the proposed method allows high-resolution ability to indicate the equality of absolute values of positive and negative values.

10 negative voltages at the output of the DAC, regardless of the magnitude of the error and instability of the parameters of measuring instruments.

The selected mode is optimal for the proposed indication method, since it provides the minimum value of the errors with this measurement method. Thus, analysis of expressions (1-3) implies that a change in the parameters of the function, which sets the voltage form at the DAC output, for example, n% of the proposed, results in the output of the error signal (asymmetry) proportional to the product J ± n, (U

25, p), which ultimately violates the stress symmetry indication mode.

Claims (1)

Invention Formula A method for monitoring bipolar digital-to-analog converters, based on an indication of the symmetry of the output voltages of a rotatable digital-to-analog converter, consisting of 35 the formation of equal in amplitude and opposite in signs of the first and second output voltages of the turned digital-analog converter, by applying to its inputs the corresponding codes, 40 forming a symmetry signal of the generated output voltages with its subsequent indication, characterized in that, in order to improve accuracy, after the formation of each output voltage of the 45 strains, an additional voltage corresponding to its zero output voltage is formed at the output of the calibrated D / A converter by supplying to the inputs of the corresponding code; in this case, the codes at the inputs of the turnable digital-to-analog converter are interleaved with a specified frequency; and symmetry as the last 55 select the harmonic component of the output voltage of the digital-to-analog converter being amplified at twice the given frequency. Zll Lit FIG. one t / t FIG. 2