JPH01227525A - D/a converter - Google Patents

Abstract

PURPOSE:To correctly measure the resistance connected in series of a low order digit D/A converter without being influenced with a noise, etc., by providing a switching element to impress a bias potential to the resistance voltage divider of the low order digit D/A converter. CONSTITUTION:The title converter is equipped with a high order digit D/A converter 3 and a low order digit D/A converter 4 to have a high order digit decoder 1 and a low order digit decoder 2 to decode digital data to be inputted and resistance voltage dividers composed of the series connection of plural unit resistances to prepare an analog data value according to the data to be decoded, and with a switch 8 for impressing the bias potential to the resistance voltage divider of the low order D/A converter 4. Consequently, when a signal is given from a test control circuit Q1 so as to turn on the switch 8, the voltage is impressed from a bias power terminal 5 to resistances r1-r256 of the resistance voltage divider of the low order side D/A converter 4. Thus, the accuracy of the resistance can be easily and correctly measured without being influenced by the noise, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a D/A converter, and particularly to a D/A converter using a resistive voltage division method.

[Conventional technology]

Conventionally, this type of resistive voltage division type D/A converter divides input digital data into upper digits and lower digits, inputs them to different D/A converters, and performs respective D/A conversions. Analog data corresponding to the digital data was obtained using a resistance voltage divider in the device, and the relative ratio of the upper and lower digits of the analog data was calculated and added to output one analog data.

Figure 2 shows a conventional 16-bit D/A converter using a resistor voltage division method. AO to A15 are input terminals for digital data, and the digital data input to input terminals AO to A7 is input to the lower digit decoder. and input end 1,000 people 8~A
The digital data input to 15 is input to the upper digit decoder. Since the lower digit decoder 2 and the upper digit decoder 1 each decode 8-bit digital input, they each have 21=256 output signal lines, and the 256 output signal lines of the lower digit decoder 2 are used for lower digit D/A conversion. 256 output signal lines of the upper digit decoder 1 are connected to the upper digit D/A converter 3.

The analog output of the upper digit D/A converter 3 and the analog output of the lower digit D/A converter 4 were connected to an adder 6, and the added output was connected to the output terminal B1. .

[Problem to be solved by the invention]

Lower digit D/A converter 4 of the conventional D/A converter described above
The full scale value of is approximately 1 of the upper digit D/A converter 3.
[: LSBE.

For example, when the bias power supply 5 is 5 [V], 1 (:LSB) of the upper digit D/A converter 3 is the lower digit D/A converter 3.
Equal to the full scale of converter 4, this value is 5 [V]
÷2”; 19CmV].

On the other hand, 1 (LSB) of lower digit D/A converter 4 is 19[
: mV] ÷ 2"#76 (μV). Therefore, when measuring the accuracy of the series resistance of the D/A converter 4 of the lower digit, 1 [:LSB:] is extremely 76 [μV]. Since it is small, it is easily affected by noise, etc., and has the disadvantage that it is difficult to measure accurate values and it takes time to measure.

SUMMARY OF THE INVENTION An object of the present invention is to provide a D/A converter that can accurately measure series-connected resistances of lower-digit D/A converters without being affected by noise or the like.

[Means to solve the problem]

The D/A converter of the present invention uses an upper digit decoder for decoding input digital data, a lower digit decoder, and a resistive voltage divider consisting of a series circuit of a plurality of unit resistors to respond to data decoded by these decoders. an upper-digit D/A converter and a lower-digit D/A converter that generate analog data values, and addition that adds the analog outputs of the upper-digit D/A converter and lower-digit D/A converter. a switching element that switches the application of a bias potential to a series circuit consisting of a resistance voltage divider of the upper digit and lower digit D/A converters, and a resistance voltage divider of the lower digit D/A converter;
It has a control circuit that controls 0N10FF of the switching element.

According to the present invention, a resistor voltage divider that generates analog data according to digital data decoded by a decoder, a switch connected between a predetermined resistance connection point of the resistor voltage divider and a predetermined voltage terminal; A D/A conversion device including the following can also be obtained.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. AO to A15 are
It is an input terminal for digital data, and includes an upper digit decoder 1 that decodes the input digital data, a lower digit decoder 2, and a plurality of unit resistors connected in series to generate an analog data value according to the decoded data by these decoders. having a resistive voltage divider configured by connecting
The upper digit D/A converter 3, the lower digit D/A converter 4, the adder 6 which adds the analog outputs of these upper digit D/A converters 3 and the lower digit converter 4, and the lower digit D/A converter 4, A converter 4
switch 8 for applying a bias potential to the resistive voltage divider of
and a test control circuit Q1 for controlling the switch 8.

The circuit of the present invention operates exactly the same as the conventional example, the circuit shown in FIG. 4 resistance voltage divider resistance (rl-r2-...-]25
5-] 256) from the bias power supply terminal 5, the accuracy of the resistance can be easily and accurately measured without being affected by noise or the like.

In addition, when measuring the resistance of the resistance voltage divider of the upper side D/A converter 3, the test control circuit Ql controls the switch 8.
is turned OFF, and a series circuit (r 1-r 2-
A bias potential is applied to ``-r256-R1=-R255-R256).

Further, during actual use, the switch 8 also serves as an input protection function to prevent voltage from being inadvertently applied to the lower digit D/A converter 4.

[Effects of the Invention] As explained above, according to the present invention, by applying a bias voltage to both ends of the lower digit D/A converter, the full scale of the lower digit D/A converter can be expanded to the bias voltage. You can. Therefore, the resistance accuracy of the lower digit D/A converter can be measured with high precision.

Furthermore, when investigating the characteristics of a D/A converter, first measure the linearity of the lower digit D/A converter using the present invention, and then measure the linearity of the lower digit D/A converter and the higher digit D/A converter. By measuring the relative accuracy and measuring the linearity of the upper digit D/A converter, it is possible to measure the characteristics with higher precision.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a D/A converter according to the present invention, and FIG. 2 shows a conventional D/A converter. AO~A15...Digital data input terminal, B
1...Analog data output terminal, R1 to R25
6゜r1~r256...Resistance, Ql...
・Test control circuit, 1... Upper digit decoder, 2...
...lower digit decoder, 3...upper digit D/A converter, 4...lower digit D/A converter, 5...
...Bias power supply terminal, 6...Adder, 7...
...MOS) transistor, 8... river switch. Agent Patent Attorney Uchihara Oto 81

Claims (1)

[Claims] A resistor voltage divider having a plurality of resistors connected in series between a decoder that decodes digital data, a power supply that generates analog data according to the digital data decoded by the decoder, and a predetermined intermediate point between the resistor voltage divider. 1. A D/A converter comprising a switch connected between a connection point and a predetermined voltage terminal.