JPH04154320A - A/d converter - Google Patents

Abstract

PURPOSE:To simultaneously execute plural A/D conversions and to reduce a conversion time by providing plural switches for selecting a split voltage of a resistance and comparators, and sequential comparison registers. CONSTITUTION:To sequential comparison registers 9, 10, an initial value of a comparison voltage is set, and inputted to a D/A converter 5 of an R-string type. By inputs from these sequential comparison registers 9, 10, one of switches S1,1 to S1,16, and one of S2,1, to S2,16, are turned on, and comparison voltages VREF1, VREF2 obtained by dividing a resistance 6 are inputted to a comparator 7 and a comparator 8, respectively. A result of comparison by the comparator 7 and the comparator 8 is inputted to sequential comparison registers 9, 10, and the control is executed so that the output voltages VREF1, VREF2 from the D/A converter and analog input voltages VIN1, VIN2 coincide with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an A/D converter, and particularly to an A7/D converter circuit of an R string successive approximation type and a voltage comparison type.

[Conventional technology]

FIG. 3 is a block diagram showing a successive approximation type A/D converter incorporating a conventional R-string type D and A converter.As shown in FIG. The output voltage V*tvx from the converter 11 and the input analog voltage VIN are input to the comparator 12, and the successive approximation register 13 is sequentially compared starting from the most significant bit MSB so that the two voltages match, and the digital output is performed. V□ut
+ is obtained. Converting a plurality of analog input voltages to a digital signal requires a conversion time that is multiple times the time to convert one analog input voltage to a digital signal.

[Problem to be solved by the invention]

The conventional R-string successive approximation type A/D converter described above requires multiple conversions at the same time when trying to convert multiple analog inputs at high speed.
The number of /A converters must be increased by the number of A/D converters, and in order to realize an A/D converter circuit of a plurality of highly accurate successive apparators, a large area is required on a semiconductor integrated circuit.

An object of the present invention is to solve the drawbacks of the conventional successive approximation A/D converter and to provide one R-string type D/D converter.
To provide an A/D converter that can be realized with an A converter, that can be realized with an extremely small area on a semiconductor integrated circuit, and that can simultaneously exchange multiple analog inputs to reduce conversion time. There is a particular thing.

[Means to solve the problem]

The configuration of the A/D converter circuit of the present invention includes one R string and a switch provided at each division point so that the voltage divided by this R string can be taken out.
It is characterized in that it includes a /A converter, a plurality of comparators, and a plurality of successive approximation registers, and is capable of performing a plurality of D/A conversions at the same time.

〔Example〕

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

FIG. 1 is a block diagram of an A/D converter according to the present invention.

In FIG. 1, the A, "D converter of this embodiment is an R string type D/A converter 1 composed of a plurality of switch circuits 1@S +, 1 □ S 1.J and a resistor 2 in series. , i comparators 3 , and i successive approximation registers 4 .

The present embodiment will be explained as a 4-bit, 2-channel successive approximation type A/D converter with reference to FIG.

In the case of the 4-bit, 2-channel A/D converter shown in FIG. 2, the R string type D/A converter 5 has two switches.
4×2 are required, and first the ratio M! is stored in the successive approximation register 9.10. Set the initial value of the pressure and connect the R string type D/A.
Input to converter 5. The input from this successive approximation resistor 9.10 causes one of the switches S1.1 to S1, +6 and +82.1 to S2. One of them up to +6 is ONL, and the comparison voltage VRE□ is obtained by dividing resistor 6.

VREF2 is input to comparator 7 and comparator 8, respectively. The analog input voltage VIN1 is simultaneously input to another input of the comparator 7, and the analog input voltage VIN2 is input to the other input of the comparator 8. The result compared by the comparator 7 is input to the successive approximation register 9, and the result compared by the comparator 8 is input to the successive approximation register 10, and the output voltage from the D/A converter is V REFI ,
V REF2 and analog input voltage V INI, V I
The successive approximation registers 9 and 10 are compared sequentially from the most significant bit MSB so that N2 match, and since the feedback comparison method is used, a 4-bit digital output V is generated. UTII VOU2 is obtained.

Therefore, a switch and a comparator to select the dividing voltage of the resistor,
By having multiple successive approximation registers, multiple A
/D conversion can be performed simultaneously.

〔Effect of the invention〕

As explained above, the present invention is particularly characterized by: In order to realize a U-number successive approximation type A/D converter circuit, it can be realized with one R string type D/'A converter, and the R string that occupies the largest area on the mask layout is shared. Therefore, it can be realized with an extremely small area on a semiconductor integrated circuit, and furthermore, when a plurality of A/D conversions are performed, the conversion time can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an A/D converter according to an embodiment of the present invention, and FIG. 2 is a 4-bit,
FIG. 3 is a block diagram showing a two-channel successive approximation type A/D converter. FIG. 3 is a block diagram showing a conventional successive approximation type A/D converter. 1.5.11...R string type D/A converter, 2.
6...Resistance, 3.7.8.12...Comparator, 4°9
．． 10.13...Successive approximation register.

Claims (1)

[Claims] A D/A converter having one R string and a switch provided at each division point so that the voltage divided by the R string can be taken out, a plurality of comparators, and a plurality of successive approximation registers. What is claimed is: 1. An A/D converter, characterized in that it is capable of performing multiple D/A conversions at the same time.