SU1481892A1 - Digital-to-analog converter - Google Patents

Abstract

The invention relates to the field of automation and computer technology and can be used in analog-digital converters and calibrators. The purpose of the invention is to improve accuracy. The digital-to-analog converter contains the first code-current converter 1, performed on the current source and the code-controlled current divider, the second code-current converter 2, the arithmetic unit 3, made in the form of a controlled subtractor, subtractors 4, 5, and the control unit 6. The introduction of a second code-current converter 2, a controlled subtractor, and two subtractors 4, 5 makes it possible to increase the accuracy of the digital-to-analog converter by compensating for the error of the code-controlled current divider. 1 il.

Description

О ОО

oo to

tsD

Output

The invention relates to automation and computing and can be used in analog-digital converters and calibrators.

The purpose of the invention is to improve accuracy.

The drawing shows the functional diagram of the digital-to-analog converter.

The digital-to-analog converter contains the first converter 1 code - the current made on the current source 1.1 and the co-controlled divider consisting of 1.2.1-1.2.P current dividers, 1.3.1-1.3.P current switches, and bit 1.4.1 -1.4. P, second code-current converter 2, arithmetic unit 3, made in the form of a controlled subtractor, second 4 and third 5 subtractors and control unit 6.

Digital to analog converter works as follows.

The output current 10 of the current source 1.1 is fed to the input of the current divider 1.2.1 and is divided so that from its output the currents go to the inputs of the current switch 1.3.1, the nominal values of which are 1/2 10. One half of the current 0 is used as the bit current and through the bit key 1.4.1 is fed to the direct or inverse outputs of the first converter 1 code - current depending on the input convertible code of the digital-to-analog converter, and the other half of the current 10 is fed to the input of the next divider 1.2.2 current and is divided into two equal parts. The second bit of the first converter 1 code - the current works similarly to the first: one part of the current is equal to 1/4 10, through the bit switch it goes to the direct or inverse outputs of the converter 1 code is the current, and the other part of the current is also equal to 1/4 It is fed to the input of the next current divider. The remaining bits of the first converter 1 code - current work in a similar way, with the exception of the last bit, in which one of the outputs of the switch 1.3.p is connected to the bus of zero nor potential. The state of all bit keys depends on the value of the input code. On command from the control unit b, all the switches of 1.3 currents can interchange their output currents, resulting in an error output

0

five

0

five

0

5 l

0

five

In this case, the current of the converter 1 code - current changes its sign, and the modules of these errors are equal.

The digital-to-analog conversion by the first converter 1 code - the current is carried out in two cycles, with t in the first cycle the conversion is performed in one state of switches 1.3.1-1.3.P, and in the second cycle - in the opposite state. On the first / clock cycle, the second subtractor 4 subtracts the output signal of the second converter 2 code - current from the output signal of the inverse output of the first converter 1 code - current and, on a command from the first output of control unit 6, the result of the subtraction is stored in the sample and storage device. In the second conversion cycle, the output of the second subtractor 4 is subtracted from the output signal of the sampling and storage device by the first subtractor 3.2, the result is fed to the input of the subtractive third subtractor 5. The subtractor subtracts the output of the controlled subtractor 3 from the output signal, the direct output of the first converter 1 code - current. The result is the output of a digital-to-analog converter.

Achieving higher accuracy in the digital-to-analog converter obes-1 is prepared as follows.

Let some input code in the ideal case correspond to an output signal equal to U. Denote the output signal of the second converter body 2 code — current U2, and output signals of the first converter 1 code — current at the inverse output at the first conversion cycle U, and at the second cycle U . Then

U-g U + &g; and, U + TH ,,;

U U - and, where and if the errors of the first and

The second transducer code is current, respectively.

Accuracy A, change em sign in

re

as a result of switching current switches. The output of the second subtractor 4 at the first conversion cycle

Ul

vm

k, (and; - i4 + and

VM

J 1481892 4

where K1 is the transfer coefficient of the short-term stability of the subtractor 4; telles 3.2, 4 and 5 can be realizable B4 error of the subtractor 4. But the command from the control unit 6 has the result U stored in the sample and hold device.

On the basis of operational amplifiers, the sampling and storage device is on a serial microcircuit (for example, K1100SK2; and the control unit 6 is based on a pulse distributor consisting of a series-connected JQ generator, counter, and decoder.

The output of the second subtractor 4 at the second conversion cycle

U

64

 to / and; - ia + je4,

at the same time at the output of the controlled subtractor 3

U

V8

-K im i; „+ U. 2 KlKiV

Uv

where Kg is the transfer coefficient, the control result of the conversion is formed at the second conversion cycle and the signal of its readiness can be the leading edge of the pulse that controls switching the switches of the currents of the first converter 1 code - current. To eliminate errors due to moment coincidence

error correction subtractor with the moment

L56- error of controlled shift of the code being converted, unit 6 of the control 3.eraging can be synchronized

Designating the output signal as the first external signal coinciding with the transducer 1 code is the current at the direct change of the converted code. the output of Uf, on the second cycle, the conversion can also be significantly reduced by using

have u, u + uE, then output

the output signal of the digital-to-analog converter is

low pass filter connected to the output of the digital-to-analog converter.

U

out

U, - K3U yg + uBf U +

thirty

+ L, - 2, - K3DP + D65, where K3 is the transfer coefficient

Claims (1)

Invention Formula A digital-to-analog converter containing an arithmetic unit, the first subtractor 5 through input 35 to the transducer code converter is the current to be readable, which is found on the current source and the co-controlled current divider whose reference input signal is connected to the:: output of the current source and the control input Q 6S - error of the third subtractor. Input transfer ratio the decremented third subtractor you - 40 is connected to the first output of the block is taken equal to one. If you choose K 3 T / 2 K, then UBm-U-L, in / 2 K B5 Thus, the output signal of the D / A converter is free from the errors of the first 1 and i second 2 code-current transducers up to the equality K. K. 1/2 K. The accuracy of this equality is determined by the accuracy of the controlled subtractor 3 and the third subtractor 5. As the second converter of its second converter, the code is the current and 2 code - current can be used almost any commercially available digital-to-analog converters with current. high yield and high the first input of the controlled subtractor, the second input of which is connected to the second output of the control unit, and the output is connected to the input of the subtracted On the basis of operational amplifiers, the sampling and storage device is on a serial microcircuit (for example, K1100SK2; and the control unit 6 is based on a pulse distributor consisting of a series-connected Q generator, counter and decoder. The exact result of the conversion is formed at the second conversion cycle and the signal of its readiness can be the leading edge of the pulse that controls the switching of the switches of the currents of the first converter 1 code - current. To eliminate the error low pass filter connected to the output of the digital-to-analog converter. Invention Formula Comparison, characterized by the fact that, in order to improve accuracy, the arithmetic unit is designed as a controlled subtractor and entered into the second code-current converter, the first and second subtractors, the output of the last of which is an output bus, the input of the decremented second subtractor is connected to the direct output the code-controlled current divider, the inverse output of which is connected to the input of the decremented first subtractor, the input of the readable and the output of which are connected respectively to the output the first input of the controlled subtractor, the second input of which is connected to the second output of the control unit, and the output is connected to the input of the subtracted b14818926 The second subtractor, the information information inputs of the code control e-inputs of the second converter of the code current divider and the input current are combined with the corresponding bus.