JP2002094379A - Multi-channel analog to digital converter, system and x-ray sensor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an analog to digital converter that can carry out analog to digital conversion on a multi-channel analog signal at a high-speed without using a high-speed analog to digital converter and conduct analog to digital conversion with high accuracy by minimizing the errors among the channels. SOLUTION: Analog to digital converters 28-1,..., 28-n respectively apply analog to digital conversion in sequence. Thus, even low-speed analog to digital converters can apply high-speed analog to digital conversion to multi-channel analog signals. A multiplexer 32 sequentially selects digital signals of each sequence and provides an output of the digital signal by each channel. Since the switching of each channel signal by the multiplexer 32 is conducted, after the conversion has been conducted on the digital signal, conversion errors among channels due to distortion in the signal caused by a difference from the signal path will not be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel AD converter that includes an amplifier (amplifier), a low-pass filter, a sample-and-hold circuit, an AD (analog-digital) converter, and a multiplexer to AD-convert a multi-channel input signal. The present invention relates to an apparatus, a system, and an X-ray sensor module. In particular, the invention provides, for example,
The present invention relates to a multi-channel A / D converter suitable for performing multi-input A / D conversion of several tens of channels or more to minimize errors between channels and performing high-accuracy and high-speed digital conversion.

[0002]

2. Description of the Related Art A conventional multi-channel AD converter of this type is shown in FIG.
No. 50). In this multi-channel AD converter, A
Multi-channel analog input signals 1, ... n to be D-converted
(N: positive integer) are the preamplifiers 10-1,.
After being amplified by 10-n, only the analog input signal of one channel is sequentially selected by the multiplexer 12. Unnecessary high-frequency components are removed from the selected analog input signal by the low-pass filter 13, and the analog signal from which the high-frequency components have been removed is amplified again by the main amplifier 14 and sampled and held by the sample-and-hold circuit 15. . While the sample and hold circuit 15 performs sample and hold, the AD converter 16 performs AD conversion, and the latch 17 holds the digital data after the AD conversion.

When the A / D conversion for one channel is completed in this way, the multiplexer 12 is switched, and the analog signal of the next channel is sent to the low-pass filter 13, and similarly, the A / D conversion of the next channel is performed. Is performed.

On the other hand, as an A / D conversion device for performing A / D conversion at high speed, there is a device described in Japanese Patent Application Laid-Open No. 61-122741. In this AD converter, a plurality of sample-hold circuits and AD converters are arranged in parallel, a plurality of analog signals from one input terminal are AD-converted by a plurality of AD converters, and the speed of the AD conversion is increased.

[0005]

However, the former AD converter has the following problems.

First, since a single AD converter 16 converts a multi-input analog signal, the AD converter 16 is required to have a high speed in accordance with an increase in the number of inputs, which is problematic in terms of cost and structure. Occurs.

A multi-channel preamplifier 10-
The analog signal from 1,...
2, the signal is guided to the low-pass filter 13, so that the analog signal of each channel is
The signal path from 1,... 10-n through the multiplexer 12 to the low-pass filter 19 differs between channels. As described above, since the signal paths are different between the channels, the load conditions of the preamplifiers 10-1,..., 10-n cannot be made the same, and the analog signal sensitive to noise is switched by the multiplexer 12. Although the analog signal is amplified by the preamplifiers 10-1,..., 10-n, the analog signal is distorted and becomes a basis for generating a conversion error between channels. Analog signals, unlike digital signals, are affected by different signal paths, causing distortion. Further, when switching by the multiplexer 12, until the influence of the previous signal is eliminated,
It takes some time until the original signal stabilizes, and the timing to start AD conversion must be delayed,
As a result, the substantial AD conversion time is shortened. As a result, a higher-speed AD converter is required.

On the other hand, when the latter A / D converter is used for multi-channel A / D conversion, a preamplifier, a multiplexer, a low-pass filter, and a main amplifier are provided in front of the one input terminal as in the conventional example of FIG. Thus, the analog signal is switched by the multiplexer at the preceding stage of the sample and hold circuit. In this case, just like the former AD converter, each analog signal passes through the multiplexer, and the signal path between the channels is different. Therefore, the load conditions of the respective preamplifiers cannot be made the same, resulting in signal distortion. There is a problem that a conversion error occurs between channels. Further, as a new problem, when a plurality of analog signals are sampled by a plurality of sample-and-hold circuits, signal paths between channels from one main amplifier to a plurality of sample-and-hold circuits are different. Are not the same,
There is a problem in that the signal is distorted and the conversion error between channels is further promoted.

As described above, in each of the above conventional AD converters, analog signals of multiple channels are switched by the multiplexer, and the signal paths of the analog signals are different for each channel. There is a problem that a conversion error occurs between them.

Therefore, an object of the present invention is to provide a high-precision A / D converter for multi-channel analog signals without using a high-speed A / D converter, and minimizing errors between channels. An object of the present invention is to provide a multi-channel AD converter capable of AD conversion.

[0011]

In order to solve the above problems, a multi-channel AD converter according to the present invention comprises an amplifier,
In a multi-channel A / D converter that includes a low-pass filter, a sample-and-hold circuit, an A / D converter, and a multiplexer, and performs A / D conversion of a multi-channel input signal,
It is characterized in that each channel is provided with a single line composed of an amplifier, a low-pass filter, a sample-and-hold circuit, and an AD converter, and a multiplexer for switching and outputting the outputs of the plurality of AD converters.

According to the above configuration, the analog input signal of each channel is processed through each of the independent streams, and is AD-converted by a separate AD converter. The digital signal from each AD converter is selected by a multiplexer and output.

As described above, since the analog signal of each channel is AD-converted by the AD converter of each series, each AD signal is converted.
Even if the converter itself is low-speed, all AD converters can perform high-speed AD conversion on multi-channel analog signals.

The signal passing through the multiplexer is
Since the digital signal has been converted by the AD converter, even if there is a difference in the signal path from each AD converter to the multiplexer, it is hardly affected. Therefore, an error between each channel can be minimized, and highly accurate AD conversion can be performed. If an analog signal that is susceptible to noise before AD conversion passes through a multiplexer as in the conventional example, distortion occurs and an error occurs between channels.

In one embodiment, the plurality of series of amplifiers, low-pass filters, sample-and-hold circuits, and A
Each of the D converters has substantially the same circuit parameters in the same circuit for all the streams, is arranged in the same positional relationship on a chip, and the plurality of streams and the multiplexer are integrated into one chip. ing.

According to the above-described embodiment, each of the amplifier, the low-pass filter, the sample-and-hold circuit, and the AD converter has substantially the same circuit parameters in all the circuits, and has the same circuit parameters on a chip. And the plurality of streams and the multiplexer are integrated into one chip, so that errors in steps such as exposure and etching when manufacturing an integrated circuit can be made the same between the respective streams, and as a result, Conversion errors between channels can be minimized.

In one embodiment, the blocks for each sequence are aligned, and each block is separated from the adjacent block by a guard link. A dummy block having a configuration is arranged.

According to the above embodiment, since each of the blocks is surrounded by the guard ring, interference between the blocks is reduced. Therefore, the accuracy of multi-channel AD conversion is improved. Furthermore, since the blocks at both ends are adjacent to the Dermi block, the conditions around the blocks at both ends,
The environment becomes the same as other blocks, and errors between blocks can be reduced.

In one embodiment, the amplifiers of each of the above series,
The low pass filter, the sample hold circuit, and the AD converter are shielded by a metal wiring layer.

According to the above embodiment, since external noise is blocked by the metal wiring layer, it is possible to prevent analog signals from being disturbed.

The system according to one embodiment includes the multi-channel AD converter and another digital circuit, and is integrated into one chip.

According to the above-described embodiment, the high-speed, high-precision AD converter and other digital circuits are integrated into one chip, which is a so-called system-on-chip. Can be done and useful.

An X-ray sensor module according to one embodiment includes the multi-channel AD converter.

According to the above-described embodiment, since a multi-channel AD converter capable of high-speed and high-precision AD conversion of a multi-channel analog signal is used, a moving image which has been difficult in the past can be realized.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

As shown in FIG. 1, this multi-channel AD
The conversion device includes a preamplifier 20-1 and a low-pass filter 2 for each system for each of the multi-channel inputs 1,.
2-1 Main amplifier 24-1, sample hold circuit 26-1, AD converter 28-1, latch 30-1, ...
Preamplifier 20-n, low-pass filter 22-n, main amplifier 24-n, sample and hold circuit 26-n, A
A D converter 28-n and a latch 30-n are provided. The digital signals from the latches 30-1,...
The output is switched by the multiplexer 32.

In the above configuration, for example, the analog input 1 is amplified by the preamplifier 20-1, the unnecessary high-frequency components are removed by the low-pass filter 22-1, and amplified again by the main amplifier 24-1. The hold circuit 26-1 holds the data for the time for performing the AD conversion. During this time, the AD converter 28-1 is connected to the sample hold circuit 2
The output of 6-1 is AD-converted, and the digital data after AD conversion is held in the latch 30-1. The other inputs 2,... N are processed in the same manner, and the latches 31-2,.
-N.

Thereafter, the multiplexer 32 sets the latch 31
-1,... 31-n are sequentially selected and digital signals are output one channel at a time.

In the above-mentioned AD conversion, AD conversion is simultaneously performed in a plurality of AD converters 28-1,..., 28-n in a plurality of streams. Can be converted.

The switching of the signal of each channel by the multiplexer 32 is performed by the AD converters 28-1,.
After the conversion into a digital signal with -n,
There is no change in the digital value of the signal, and no conversion error occurs between channels. Therefore, a high-precision and high-speed A / D converter can be realized despite the large number of channels.

If the multi-channel AD converter is
If the components are to be configured with individual components, it becomes more difficult to make the parameters between the channels the same as the number of channels increases. Therefore, in this embodiment, a plurality of channels are integrated into one chip using integrated circuit technology. Then, in making one chip, for example, a pre-amplifier 20-1, a low-pass filter 22-1, a main amplifier 24-1, a sample-and-hold circuit 26-1, an AD converter 28-1, a latch which constitutes one channel for one channel Reference numeral 30-1 denotes a preamplifier 20 that constitutes another series.
-N, low-pass filter 22-n, main amplifier 24-
n, sample and hold circuit 26-n, AD converter 28-
n, the same circuit and the same parameters as the latches 30-n. As a result, each channel has the same performance, and errors between channels can be eliminated. When arranging these circuits on a chip, the circuits constituting each channel are arranged in the same positional relationship on the chip to further reduce the error of analog signals between channels. FIG. 2 shows an example of this arrangement. In FIG. 2, the conversion block 35-1 includes a sequence corresponding to the input 1 in FIG. 1, that is, a preamplifier 20-1, a low-pass filter 22-.
1, main amplifier 24-1, sample hold circuit 26
-1, an AD converter 28-1, and a latch 30-1. Similarly, the conversion blocks 35-m and 35-n are blocks corresponding to the input m and the input n. Then, each of the conversion blocks 35-1,..., 35-m,.
n is the same circuit and the same parameter as described above. These blocks 35-1,..., 35-m,
, 35-n are arranged in the same positional relationship on the chip. Therefore, errors due to the directionality of exposure, etching, and the like, which occur when an integrated circuit is manufactured, can be made equal in the sections of the conversion blocks 35-1,..., 35-m,. Can be minimized.

Thus, each conversion block 35-
, 35-m,..., 35-n are made the same circuit and the same parameter, and are arranged in the same positional relationship on the chip by using CAD / CAE, which is the current LSI design environment. Can be realized.

Further, each conversion block 35-1,
, 35-m,..., 35-n are separated by being surrounded by a guard ring (not shown).
, 35-m,..., 35-n can be reduced to improve accuracy. As the guard ring, a well layer,
The use of the diffusion layer does not cause an increase in special masks and processes. Then, as shown in FIG. 2, the dummy blocks 34,
38 are provided. The dummy blocks 34 and 38 are
35-m,..., 35-n, but are not necessary for the original operation. By doing so, the chip size slightly increases, but the conversion blocks 35-1 and 35-
n, the conditions and environment around the conversion blocks 35-1, 35-n are different from those of the other conversion blocks 35-2,.
, 35,..., 35
.., 35-n.

Further, in this embodiment, the upper surfaces of the conversion blocks 35-1,..., 35-m,..., 35-n and the dummy blocks 34 and 38 of FIG. This prevents noise from getting on the analog signal.

As described above, the multi-channel A / D converter has high accuracy and high speed, and therefore has a wide application range and is used in various systems. On the other hand, with the advance of semiconductor technology, the system has been integrated into one chip, and the era of the system-on-chip has been entered. Therefore, by incorporating the multi-channel AD converter of the above embodiment into this system-on-chip, the usefulness of the system can be further enhanced.

FIG. 3 shows a configuration of an X-ray sensor module using the multi-channel AD converter of the present invention. Here, the sensor screen 42 displays the X illuminated on the screen.
Although not shown, the vertical and horizontal 288 are used to convert the lines into electric charges.
0, X-ray conversion elements of 2880 × 2880 pixels are arranged, and a TFT (thin film transistor) for taking out generated charges is arranged under each X-ray conversion element for each X-ray conversion element. . Further, a gate driver circuit 40 and a signal conversion circuit 41 are provided to extract a signal from the X-ray conversion element.

FIG. 4 is a circuit diagram showing a part of the X-ray conversion element taken out to explain the operation of the X-ray sensor module. Here, the total number of gate lines is 2,880, but the operation is divided into two, and the signal reading is controlled so that only one of the 1440 lines is selected. Therefore, when the gate line 58 is selected, the TFTs 50 and 52 are turned on, and only the electric charge generated by the X-ray conversion element 54 is read out to the data line 60, and similarly, the X-ray conversion Only the charge generated in the element 56 is read. The signals read to the data lines 60 and 61 are digitized by a signal conversion circuit 41 incorporating the above-mentioned AD converter.

Then, the signals of the individual X-ray conversion elements are read out, digitized, and sent to a display device such as a CRT (cathode ray tube) or a liquid crystal display device, where the X-ray image is converted. Can be reproduced. At this time, in order to reproduce a moving image, the A / D conversion time of a signal read from one X-ray conversion element is 30 screens per second, and 1440 is used for 1440 lines.
To compose the screen, as shown in the following equation, 23 μs
It is as follows. Although the total number of data lines is 2880, since it is divided into two, 1440 constitutes one screen.

1 second ÷ 30 screens ÷ 1440 lines ≒ 23 μs Next, when AD conversion of the signal read to the data line is performed by applying the prior art of FIG.
The signal of line 0 is processed by one AD converter, and the required conversion processing speed is 1 as shown in the following equation.
A high speed of 25 MHz is required.

1 second ÷ 23 μs × 2880 lines ≒ 125 MHz Therefore, as in the case of the gate line, even if the data line is divided into two, a high speed of 70 MHz is required. Also, X-ray sensor modules are required to have high accuracy, and
The conversion precision also requires 14 bits.

Therefore, it has been difficult to realize an X-ray sensor module that satisfies this requirement with the configuration of the prior art. However, the multi-channel AD converter of the embodiment shown in FIG. 23μs (44KH
z), and can be realized with an AD converter that is much slower than the conventional technology. Therefore, in this embodiment, although it takes a long conversion time, a highly accurate Δ-Σ AD converter can be adopted. The signals of 2880 lines are input 1 ... in FIG.
n, high-speed, high-precision AD conversion becomes possible.

Further, an LSI of a multi-channel AD converter is provided.
Since it is difficult to put 1440 or 2880 input signals into one chip per package due to the limitation of the number of terminals of the package, in this embodiment, 128
The input of the book was one chip.

As described above, with the X-ray sensor module of this embodiment, a moving image that was difficult with the prior art could be reproduced.

The multi-channel A / D converter of the above embodiment includes both the preamplifier and the main amplifier, but may include only one of them.

[0045]

As is clear from the above, according to the present invention, the analog signal of each channel is converted into the AD signal of each system.
Since each AD conversion is performed by the converter, even if the AD converter itself is low-speed, the multi-channel analog signal can be AD-converted at high speed.
Can be converted.

Further, according to the present invention, since the signal passing through the multiplexer is a digital signal converted by the AD converter, even if the signal path from each AD converter to the multiplexer is different, An error between channels can be minimized, and highly accurate AD conversion can be performed.

According to one embodiment, each of the amplifier, the low-pass filter, the sample-and-hold circuit, and the AD converter has substantially the same circuit parameters in the same circuit for all the series, and has the same on-chip structure. It is arranged in a positional relationship, and a plurality of streams and a multiplexer are 1
Since it is a chip, the characteristics of each series can be made the same,
As a result, the conversion error between channels can be minimized.

According to the first embodiment, since each block is surrounded by the guard ring, interference between blocks is reduced, and the accuracy of multi-channel AD conversion is improved.

According to the first embodiment, since the blocks at both ends are adjacent to the dermis block, the conditions and environment around the blocks at both ends are the same as those of the other blocks, and errors between the blocks can be reduced. .

According to the first embodiment, since external noise is blocked by the metal wiring layer, it is possible to prevent analog signals from being disturbed and perform highly accurate AD conversion.

According to the system of the first embodiment, the high-speed, high-precision multi-channel AD converter and other digital circuits are integrated into one chip, which is a so-called system-on-chip. Can be used and useful.

According to the X-ray sensor module of the first embodiment, since the above-described multi-channel AD converter capable of AD-converting a multi-channel analog signal at high speed and high accuracy is used, moving images which have been difficult in the prior art are used. The image can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a multi-channel AD converter according to an embodiment of the present invention.

FIG. 2 is a diagram showing an arrangement on a chip when the multi-channel AD converter according to the embodiment of the present invention is implemented as an LSI;

FIG. 3 is a diagram illustrating a configuration of an X-ray sensor module according to an embodiment of the present invention.

FIG. 4 is a circuit diagram showing a part of an X-ray conversion element of the X-ray sensor module.

FIG. 5 is a block diagram of a conventional multi-channel AD converter.

[Explanation of symbols]

10-1, 10-n, 20-1, 20-n Preamplifier 12, 32 Multiplexer 13, 22-1, 22, n Low-pass filter 14, 24-1, 24-n Main amplifier 15, 26-1, 26, 26 n sample hold circuit 16, 28-1, 28-n AD converter 17, 30-1, 30-n latch 35-1, 35-m, 35-n conversion block 34, 38 dummy block 40 gate driver circuit 41 signal Conversion circuit 54, 55, 56, 57 X-ray conversion element

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinichi Tanaka 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka F-term (reference) 2G088 EE01 EE27 FF02 FF14 GG20 GG21 JJ05 KK01 KK05 KK27 LL18 5J022 AA01 BA02 BA05 BA06 CA07 CA10 CE01 CE08 CF02 CF08 CF10 CG01

Claims (6)

[Claims] 1. A multi-channel A / D converter comprising an amplifier, a low-pass filter, a sample-and-hold circuit, an A / D converter, and a multiplexer, for performing an A / D conversion of a multi-channel input signal. A multi-channel A / D converter comprising: a hold circuit and an A / D converter; and a multiplexer for switching and outputting the outputs of the plurality of A / D converters. 2. The multi-channel AD converter according to claim 1, wherein each of said plurality of series of amplifiers, low-pass filters, sample-and-hold circuits, and AD converters is substantially the same circuit for all series. A multi-channel AD converter having the same circuit parameters, being arranged in the same positional relationship on a chip, and wherein the plurality of streams and the multiplexer are integrated into one chip. 3. The multi-channel A / D converter according to claim 2, wherein the blocks for each sequence are arranged, each block is separated from an adjacent block by a guard link, and furthermore, each block is adjacent to the block at both ends. Wherein a dummy block having the same configuration as the blocks for each series is arranged. 4. The multi-channel A / D converter according to claim 1, wherein the amplifier, the low-pass filter, the sample-and-hold circuit, and the A / D converter of each series are shielded by a metal wiring layer. Characteristic multi-channel AD converter. 5. A system comprising the multi-channel AD converter according to claim 1 and another digital circuit, and being integrated into one chip. 6. A multi-channel A / D converter comprising the multi-channel A / D converter according to claim 1.
Line sensor module.