JPS63164621A - Reference voltage generator - Google Patents

Abstract

PURPOSE:To improve the accuracy and resolution without increasing circuits by making a reference resistor and a correction resistor by the same material at the same time, directing the current flowing through the reference resistor and the correction resistor opposite to each other in a chip thereby compensating the nonlinear error between the reference resistor and the correction resistor due to the dispersion in the film thickness. CONSTITUTION:The reference resistor 1 and the correction resistor 2 are made of the same material, e.g., Al vapor-deposition film at the same time. Moreover, a voltage is applied in a way that the direction of the current flowing to the reference resistor 1 and the direction of the current flowing to the correction resistor 2 are made opposite to each other. For example, the left side of the chip in the reference resistor 1 is brought into a high potential to cause the current to flow from the left to the right of the chip. On the other hand, the right side of the chip in the correction resistor 2 is brought into a high potential to cause the current to flow from the right to the left of the chip. Thus, the tendency in the film thickness dispersion of the material used for the reference resistor 1 and the correction resistor 2 is identical in the chip and the error of the resistance due to the film thickness dispersion is correction to improve the accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a reference voltage generating device for a high-precision, high-resolution analog-to-digital converter (hereinafter referred to as ADC). The ADC will be explained below.

Conventional technology In ADCs, especially ADCs for video signals.

Parallel type ADCs have become mainstream because high speed is required. In this parallel type ADC, a reference resistor is formed using AI or the like in order to provide a reference voltage to each comparator.
For ADCs of bits or more, it is necessary to provide a correction resistor in order to achieve high resolution and high precision. A block diagram of a conventional parallel ADC with correction resistors is shown in FIG. Reference resistance 1 ('1~''1023) is A4, correction resistance 2
(R1-R9) are formed of polycrystalline silicon into which boron ions are implanted. 10 points) 10 in ADC
24 comparators 3 (C1 to C1゜24) are required, but since a small current flows into each of them from the reference resistor 1, it is busy, and as shown in Fig. 6, the comparators 3 are actually The applied potential deviates from the ideal potential and an error occurs. Therefore, any point on the reference resistance 1, for example the 64th or 1st
A potential is applied from the correction resistor 2 to every 28th point, and correction is performed as shown in FIG. However, nonlinear errors occur in the correction resistor 2 itself due to variations in film thickness, and in reality, the total nonlinear error often becomes large as shown in FIG.

be.

Problems to be Solved by the Invention In such a conventional parallel type ADC with a correction resistor, factors that cause errors include, in addition to the input current from the reference resistor to the comparator, variations in the Al film thickness of the reference resistor and correction. There are variations in the thickness of the polycrystalline silicon resistor, which depends on the vapor deposition or debostation equipment. For example, ADC
The nonlinear error of 10−! - In order to suppress the LSB, it is necessary to suppress the variation in the polycrystalline silicon film thickness within the chip to ±0.4%, but this is extremely difficult. Further, since the reference resistor and the correction resistor are each made of different materials, it is difficult to predict errors due to film thickness variations in advance and correct them using a circuit.

The present invention has been made in view of the above, and an object of the present invention is to provide a reference voltage generating device for use in a high-resolution, high-precision ADC, etc., with small nonlinear errors, without increasing the number of circuits for device improvement or correction. It is an object.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention forms the reference resistor and the correction resistor from the same material, for example At, and furthermore, the direction of the current in the reference resistor and the correction resistor is reversed. This is intended to minimize nonlinear errors caused by variations in film thickness of materials used for the reference resistor and correction resistor.

Function: As described above, in the present invention, since the reference resistor and the correction resistor are made of the same material, the tendency of the film thickness variation is the same within the chip, and furthermore, the current flowing through the reference resistance and the correction resistor is For example, if the film thickness decreases from the left to the right of the chip because the direction is reversed within the chip, the resistance increases from the left to the right in the standard resistance. However, in the case of a correction resistor, the resistance increases from right to left, and nonlinear errors due to variations in material thickness can be minimized.

Embodiment FIG. 1 is a block diagram of a parallel type ADC having a correction resistor according to the present invention. The reference resistor 1 and the correction resistor 2 are formed at the same time using the same material ratio, for example, an Al vapor deposited film. Further, a voltage is applied so that the direction of the current flowing through the reference resistor 1 and the direction of the current flowing through the correction resistor 2 are opposite to each other. For example, FIG. 2 shows a schematic diagram of the layout of the reference resistor 1 and the correction resistor 2 on an actual chip and the method of connecting them. In the reference resistor 1, the left side of the chip is set to a high potential so that current flows from the left to the right of the chip. On the other hand, in the correction resistor 2, the right side of the chip is set to a high potential so that the current flows from the right to the left of the chip. Naturally, the reference resistor 1 and the correction resistor 2 are connected so that the highest potentials and the lowest potentials thereof are the same potential. Divide the correction resistor 2 into 9 blocks, take out taps 4t from 8 locations, and number the taps 4 from the high potential side as TO, T1, . T2
．． T3゜T4. T,,T6. T7. T8. Let it be T9. The resistance value of R2-R7 is set to be R1, the resistance value of R9 on the left side, and the resistance value of R1 on the right side is i. In the case of 10-bit ADC,
The reference resistor 1 is divided into 1023 equal parts, and the number of each resistor is r, ~r, from the high potential side. 23. Tap T is between 64 and T66 of reference resistor 1, tap T2 is between T19 and r, 93, and tap T3 is r.
3□. and r3□, taps T4t-r448 and T
449 pressure, tap "5" between T576 and "577," tap "6" between T704 and T7゜6,
between r and r, tap T8 to 96° and T
96. A second Al wiring or the like is connected between them.

If the resistance value of the resistor is Rn, then the reference resistor and the correction resistor can be represented by a circuit like the one shown in Figure 3.The resistance is r.
,=rs=R,=Rs=,, e”2=ra=
``4=rs='e=r7=r8=R2=R3
It is designed so that =R4=R5=R8='7=”8=R. Now consider the case where the thickness of the Al film increases uniformly from the left side to the right side of the chip. , obviously r , /Rs ” r 9/)l ,.

r 2/R8= r 8/R2, r 3/R7= r
7/Ra, r4/R6=rt4. Also, if the resistance value of the resistor between each tap decreases by a due to the increase in the Al film, then inm! H-1('-*00) m
R,=RB-1('-*oo).

Consider the difference in resistance between T and T and between T3 and 14. If r2=12"R, then r3""2(1
100"""'-100) R7=12(1-, H stone)=
R(1-100)(1(ゐ(1驎) Similarly, r4=r2(1-1oo) ``R('-100'R
6=R2(1-ru) =R(1-box) The change in resistance value between adjacent taps in ■ and ■ is as follows. Here, if a = 1%, then even if the reference resistance between taps that match sb changes by 1 inch due to film thickness variation, by using the above correction method, it will be possible to The variation in resistance value between tags can be suppressed to 0.0151, and is effectively compensated for.

In this way, because the reference resistor 1 and the correction resistor 2t are made of the same material at the same time, the reference resistor 1 and the correction resistor 2t
By making the tendency of film thickness variation of the material used in
Errors in resistance values due to film thickness variations can be corrected, and a highly accurate ADC can be obtained. This effect becomes especially large when the film thickness changes uniformly in the left-right direction of the chip.

Effects of the Invention As described above, the present invention allows the reference resistor and the correction resistor in a parallel type ADC etc. to be formed simultaneously from the same material, and furthermore, the direction of the current flowing through the reference resistor and the correction resistor is opposite within the chip. By doing so, nonlinear errors in the reference resistor and correction resistor due to film thickness variations are compensated for each other, and it is possible to use a high-resolution, high-precision parallel type ADC equal voltage standard without increasing the number of circuits. This is a method that can realize a voltage generator, and is extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a diagram of an ADC according to an embodiment of the present invention;
Figure 2 is a layout diagram of the ADC shown in Figure 1 on the chip.
FIG. 3 is an equivalent circuit diagram of the resistor portion of FIG. 1, FIG. 4 is a block diagram of an example of a conventional ADC, and FIGS. 6, 6, and 7 are voltage characteristic diagrams in the ADC. 1...Reference resistance (r, ~r, .23), 2...
...Correction resistor (R, ~R9), 3...Comparator (C1-C1024)'4...Tap (T,
~T8). Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 + Todo C flat bottom 5δ Figure 4 Figure 5 Input turtle 5 pressure. Figure 6 Figure 7

Claims (1)

[Claims] a plurality of resistors connected between two different potentials and generating a plurality of reference voltages; and a plurality of resistors connected between two different potentials,
a plurality of correction resistors formed simultaneously of the same material as the resistor, and a current flowing through the plurality of resistors and the plurality of correction resistors is directed in a direction opposite to the direction in which they are arranged. 1. A reference voltage generating device characterized in that a highly accurate reference voltage can be obtained even when the resistance value of the resistor has variations by having a means for supplying a voltage to the reference voltage.