JPH04181814A - Analog/digital converter - Google Patents

Abstract

PURPOSE:To simplify the wiring by connecting a 1st resistor array comprising series connection of plural resistors and a 2nd resistor array comprising series connection of same number of resistors between two voltage sources respectively and arranging both the resistor arrays in parallel so that the direction of voltage drop is caused in opposite directions to each other. CONSTITUTION:Each of 1st and 2nd resistor arrays 7 consists of series connection of plural resistors and they are arranged close to each other in parallel on a same plane. Then each of voltage comparators 1 receives four signals being 1st and 2nd input voltages Vsr, Vsv from a differential input voltage generating circuit 3 and 1st and 2nd reference voltages Vxr, Vxv generated as divided voltages of the 1st and 2nd resistor arrays 7. The two resistor arrays generating a reference voltage are arranged in parallel in this way, then the generating positions of the two kinds of the reference voltages used for each voltage comparator are arranged close to each other. Thus, the connection wiring from the resistor arrays to each voltage comparator is considerably simplified.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an analog/digital (hereinafter referred to as A/D)
The present invention relates to a converter, and particularly to an A/D converter that is high-speed, highly accurate, and can reduce the area when integrated into a circuit.

[Conventional technology]

Regarding A/D converters related to the present invention, see James G. Peterson, "Monolithic Video A/D Converter," IEJ Journal of Solid State Circuits, Nisshi Vol. 14, No. 6, 932-93.
7 pages.

December 1979 (James G, Peterso
n, ”AMonolithic Video A/
D Convertor,” I EEE J,
5olid-5tate C1rcuits, Vol.
.

SC-14, No, 6. pp, 932-937. Dec
.

1979).

FIG. 10 shows the configuration of the parallel A/D converter discussed above. This consists of two voltage sources VHJI V
)l” (<VHJ) and the reference voltage VH generated as its divided voltage.
A plurality of voltage comparators 8 are provided in parallel to compare the magnitudes of the input signal V and the input signal V.
It is composed of an encoder 2 that outputs power.

[Problem to be solved by the invention]

The conventional technology with the configuration shown in FIG. 10 is a method that compares the magnitude of one reference voltage and one input signal, so there is a problem that various noises are likely to mix into the reference voltage or input signal, resulting in a comparison error. There was a point.

As a means to solve this problem, as shown in FIG. 11, a difference ΔVX (=V
χ-Vxv) and the difference between the two input signals vsY and vsv corresponding to the input signal ■5
By comparing sJ with a fully differential voltage comparator l,
It is known that a highly accurate A/D converter that is resistant to noise can be realized.

However, when adopting the configuration shown in Figure 11, the wiring is complicated because each reference voltage generated from the resistor string is branched into two and then input to each voltage comparator as shown in the figure. Therefore, there is a problem in that the area increases when integrated into a circuit.

An object of the present invention is to solve the problems of the above-mentioned fully differential voltage comparators in the prior art, and to provide an A/D converter that does not increase the area even when integrated into an integrated circuit. It's about doing.

[Means to solve the problem]

In order to achieve the above object, in claim 1 of the present invention, a first resistor string formed by connecting a plurality of resistors in series is connected between two voltage sources having different voltage values, and the same number of resistors are connected in series. A second resistor string connected in series is connected between two other voltage sources and placed parallel to the first resistor string so that the direction of voltage drop is opposite to that of the first resistor string. , means for creating a first input voltage that increases in proportion to an increase in the difference between the analog input voltage and a constant reference voltage, and a second input voltage that decreases in proportion to an increase in the difference between the analog input voltage and a constant reference voltage; One of the divided voltages is used as a first reference voltage, and one of the voltages divided by the second resistor string is used as a second reference voltage, and the difference between the first reference voltage and the second reference voltage is determined. , a plurality of voltage comparators for comparing the difference between the first input voltage and the second input voltage, and means for obtaining a digital value from the output of the voltage comparators.

In claim 2, the low voltage side terminal of the first resistance string and the high voltage side terminal of the second resistance string are electrically connected, the voltage source connected to these terminals is removed, and the first The high voltage side terminal of the resistor string is connected to a first voltage source, and the low voltage side terminal of the second resistance string is connected to a second voltage source having a lower voltage value than the first voltage source.

Further, in claim 3, the first and second resistor arrays are disposed close to each other on a plane, and the voltage comparators are provided on one side or both sides of the resistor array on the same plane. The voltage comparator array is arranged in parallel with the resistor array, and further outside the voltage comparator array, an encoder that obtains a digital value from the voltage comparator output is arranged in parallel with the voltage comparator array.

Furthermore, in claim 4, at least two or more combinations of the above-described resistor array, voltage comparator array, and encoder,
The resistor rows in each set are arranged in parallel on the same plane,
A configuration in which one end of each of the resistor strings in adjacent groups is connected by a folding wiring formed in a direction perpendicular to the direction of the resistance strings, and a common voltage source is used for all the resistance strings in the group.
/D converter.

[Effect]

According to the circuit configuration of claim 1, the generation positions of the first reference voltage and the second reference voltage required for each voltage comparator are as follows.
The two resistor arrays arranged in parallel are located close to each other, which makes it possible to simplify the connection wiring from the resistor array to the voltage comparator. According to claim 2, there is no need to provide separate voltage sources for the two resistor strings, and the entire set of voltage sources can be used. Further, according to claims 3 and 4, it is possible to realize a large-scale integrated circuit of a parallel type A/D converter with a small integrated circuit area.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 shows the configuration of an embodiment, which includes first and second resistor strings 7 that generate two reference voltages Vxyg and Vxv that are input to each fully differential voltage comparator 1, and an analog input signal V,
with respect to the first input voltage vsr and the second input voltage v6
The differential input voltage generation circuit 3 that generates the voltage V and the difference between the first and second input voltages ΔV S ("V S y '/
sy ) and the difference between the first and second reference voltages ΔVX (=VX
, -Vχ, and an encoder 2 that outputs a digital value corresponding to the comparison results of these voltage comparators.

The first and second resistor arrays 7 (in the figure, the left side is the first and the right side is the second) are each made up of a plurality of resistors connected in series, and are arranged adjacent to each other so as to be parallel to each other on the same plane. will be placed. The upper terminal of the first resistor string is connected to the voltage source of voltage value VHJ, and the lower terminal is connected to the voltage source of voltage value VH''(<VHJ
) (1) Connected to a voltage source, and the lower terminal of the second resistor string is connected to another voltage source with voltage value VHJ, and the upper terminal is connected to another voltage source with voltage value vHwI.

Each voltage comparator 1 receives first and second input voltages V$Y, V5v from the differential input voltage generation circuit 3, and first and second input voltages V$Y and V5v from the differential input voltage generation circuit 3.
The first and second reference voltages Vχ7. generated as the divided voltages of the resistor string 7. In this case, for example, the illustrated voltage comparator 1 at the top position receives the first reference voltage generated from the voltage division point at the top position of the first resistor string, and The second voltage generated from the voltage dividing point at the top of the second resistor string
A reference voltage is input.

The differential input voltage generation circuit 3 has an analog input voltage V, and
This is a circuit that creates a first input voltage Vgy that increases in proportion to the increase in the difference from a constant reference voltage, and a second input voltage Vgv that decreases in proportion to the increase in the difference. The input voltage vs and the created first . Second input voltage V$r
, vsv is shown in FIG. When the input voltage Vs is equal to the reference voltage VH'(<VHJ), V
5y=V)l” HVSV:VHJ,
Also, in the case of V, :V)IJ, V sr= VHJr
Vsr increases and VSV decreases in linear proportion to the increase in input voltage V, such that Vsv=VH''. Therefore, input voltage Vg''(VHJrVH''
)/2 as the border, ΔV 5 (= V 5r - Vsv)
will change its sign from negative to positive.

FIG. 3 shows an embodiment of the differential input voltage generating circuit 3. A capacitor C1 and a switch S are connected between the input and output of the differential amplifier 6.
, are connected in parallel, and furthermore, a capacitor C2 and a switch S2 for inputting the analog input voltage vll as AC input are connected in series to each input terminal of the differential amplifier 6, and one end of the switch S2 is connected to the input voltage v8, One end of the other switch S2 is connected to ground. Further, a short circuit switch S is connected between the connection terminals of these switches S2 and the capacitor C2. The charges stored in the AC input capacitor C2 to the differential amplifier 6 according to the input voltage V are transferred to the capacitor C1 connected between the input and output of the differential amplifier 6, with different signs but equal absolute values. Differential voltages Vgy and V5v are generated by distributing the charges.

FIG. 4 shows an embodiment of the fully differential voltage comparator 1 used in the A/D converter of the present invention. (a) is a circuit configuration diagram, in which a short-circuit switch 5WAZ is installed between the input and output of the differential amplifier 6.
Amplifiers 4 are connected in series in multiple stages, each having a capacitor C connected in series to each input terminal, and a reference voltage Vxy and an input voltage vs to the other terminal of the first stage capacitor C.
, and switches SWx, SWs, which alternately switch between the reference voltage V31V and the input voltage 'I/4Hy.
SWx and SWs are connected. Furthermore, a latch circuit 5 is connected to the final stage amplifier, which outputs a determined logical value from the output of this amplifier. Figure (b) shows a state diagram of switch opening and closing. First, the switches 5WAZ between the input and output of all differential amplifiers 6 are closed to self-bias the input and output terminals of each differential amplifier 6. At the same time, reference voltages Vx- and Vχ9 are respectively input to the first stage. Next, the switch 5WAZ between the input and output of the differential amplifier 6 is opened, and the input voltage v5A is applied to the first stage.

Vsv is applied, and ΔVχ (=Vχ, −VχV
) and 8V 5 ("V sy V sV) is amplified and output.

FIG. 5 is a circuit configuration diagram of another embodiment of the present invention (Claim 2,
and a case where voltage comparator arrays are arranged on both sides of the resistor array according to claim 3). The difference from the embodiment in FIG.
The low voltage side terminal of the second resistor string is electrically connected to the high voltage side terminal of the second resistance string, the voltage source connected to these terminals is removed, and the The voltage comparator array 1 has an encoder 2 arranged outside the voltage comparator array 1. With such a circuit configuration, for example, the first and second reference voltages Vxr and Vχ9 used for the voltage comparator 1 at the top position on the left side and the voltage comparator 1 at the top position on the right side in the diagram are The voltage generated from the voltage dividing point at the top of the first and second resistor strings can be used in common (i.e., Δ■ = V y Vxv, the absolute value is the same and the sign is positive or negative). Therefore, it becomes possible to greatly simplify the connection wiring from the resistor array to the voltage comparator array.

Figures 6 to 9 show the arrangement of an embodiment in which the A/D converter of the present invention is integrated.The parts related to input voltage are omitted, and each voltage comparator is constructed as a rectangular block. This is what is shown.

FIG. 6 is an integrated circuit block diagram corresponding to the embodiment circuit shown in FIG. place,
Connect adjacent ends to each other, and connect one end to the voltage source VH.
J and the other to the voltage source VH"(<VHJ), fully differential voltage comparator arrays are placed in parallel on both sides of the outside of this resistor array, and further parallel to the outside of this resistor array, each voltage An encoder 2 is arranged to obtain a digital value from the comparator output.

FIG. 7 is a block diagram in the case where the fully differential voltage comparator array and encoder in the embodiment circuit of FIG. 5 are arranged only on one side of the resistor array.

Figures 8 and 9 show that when the circuit scale of the resistor array, voltage comparator array, and encoder becomes larger, two or more combinations of the resistor array, voltage comparator array, and encoder are arranged on the same plane within each set. resistor arrays are arranged in parallel, and one end of each resistor array in an adjacent group is connected to each other by a folding wiring formed in a direction perpendicular to the resistor array direction, and a voltage source VHJ+ v , II are commonly used for each set of resistor strings. Figure 8 shows the case where two sets of the configuration shown in Figure 6 are arranged on the same plane so that VHJI vH'' can be used in common, and Figure 9 shows the case where two sets of the configuration shown in Figure 7 are arranged on the same plane. The case is shown in which the voltage sources are commonly used and arranged on the same plane.

[Effects of the Invention] As explained above, according to claim 1 of the present invention, a fully differential voltage comparator is used as a voltage comparator to compensate for the difference ΔVx between two types of reference voltages and the input signal VS. In an A/D converter that compares the difference Δvs between two types of input signals, by arranging two resistor strings that generate a reference voltage in parallel, the two types of voltage comparators used in each voltage comparator can be The generation positions of the reference voltages are now close to each other, which makes it possible to greatly simplify the connection wiring from the resistor string to each voltage comparator.

According to the second aspect, in addition to the above-mentioned effects, the high-voltage side voltage source and the low-voltage side voltage source can be used in common for the two resistor strings, and there is an advantage that the power supply configuration can be simplified.

According to claims 3 and 4, when a parallel A/D converter using a fully differential voltage comparator that is resistant to power supply noise etc. is integrated into an integrated circuit, the area of the integrated circuit can be significantly reduced. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing the input/output characteristics of a differential input voltage generating circuit used in the present invention, and FIG. 3 is a diagram showing the input/output characteristics of a differential input voltage generating circuit used in the present invention. A diagram showing one embodiment of the input voltage generation circuit, FIG. 4 is a diagram showing a row of fully differential voltage comparators used in the present invention, and FIG. 5 is a block diagram showing another embodiment of the present invention. 6, 7, 8, and 9 are diagrams showing circuit layouts when the A/D converter of the present invention is integrated into an integrated circuit, respectively, and Figures 10 and 11 are related to the present invention. FIG. [Explanation of symbols] 1... Fully differential voltage comparator 2... Encoder 3... Differential input voltage generation circuit 4... Amplifier 5... Latch circuit 6...
・Differential amplifier 7...Resistor string 8...Voltage comparator Junnosuke Nakamura, attorney-in-fact patent attorney Input tLv. Figure 2 Figure 3 (a) Figure 4 Figure 5 Figure 6 Figure 7 Figure 9 Figure 10 Figure 11

Claims (1)

[Claims] 1. A first resistor string formed by connecting a plurality of resistors in series is connected between two voltage sources having different voltage values, and a second resistance string is formed by connecting the same number of resistors in series. A resistor string is connected between two other voltage sources and placed parallel to the first resistor string such that the direction of voltage drop is opposite to the first resistor string, and is connected to the analog input voltage and a constant reference voltage. means for creating a first input voltage that increases in proportion to an increase in the difference between the first input voltage and a second input voltage that decreases in proportion to an increase in the difference between the first and second input voltages; The difference between the first reference voltage and the second reference voltage, with one of the voltages divided by the second resistor string as the first reference voltage, and the first input voltage. An analog/digital converter comprising: a plurality of voltage comparators for comparing the difference between second input voltages; and means for obtaining a digital value from the output of the voltage comparators. 2. Electrically connect the low voltage side terminal of the first resistance string and the high voltage side terminal of the second resistance string according to claim 1, remove the voltage source connected to these terminals, and The high voltage side terminal of one resistor string is connected to a first voltage source, and the low voltage side terminal of a second resistance string is connected to a second voltage source having a lower voltage value than the first voltage source. Analog/digital converter. 3. The first resistor array and the second resistor array according to claim 2 are arranged close to each other on a plane, and the plurality of voltage comparators are arranged on one or both sides outside of the resistor array on the same plane. A voltage comparator array is arranged in parallel with a resistor array, and an encoder that obtains a digital value from the voltage comparator output is arranged further outside the voltage comparator array in parallel with the voltage comparator array. Digital converter. 4. At least two or more combinations of the resistor array, voltage comparator array, and encoder according to claim 3 are arranged on the same plane so that the resistor arrays in each set are parallel to each other, and An analog/digital converter characterized in that one end of each resistor string is connected by a folding wiring formed in a direction perpendicular to the direction of the resistor string, so that a common voltage source is used for all the resistance strings in the set.