JPS6212213A - Analog-digital converter - Google Patents

Abstract

PURPOSE:To attain miniaturization and circuit integration while leaving advantages such as a short conversion time and less number of components by using an SAW element so as to realize a delay circuit which has been difficult for circuit integration in a travelling wave type A/D converter. CONSTITUTION:An analog signal input terminal 1 connects to a voltage comparator 2 and an SAW element 11 and a reference voltage source (Vref)4 connects to voltage comparator 2 and D/A converters of the 3 and succeeding stages. The voltage comparator 2 connects to a flip-flop 6, the flip-flop 6 connects to a D/A converter 5 and a flip-flop 7, the D/A converter 5 connects to a voltage comparator 8 and the voltage comparator 8 connects to a flip-flop 9. The SAW element 11 connects to the voltage comparator 8 and the 3rd-stage SAW element. Miniaturization and circuit integration are attained by using the SAW element for the delay circuit having been the biggest bottle neck in integrating the circuit of the travelling wave type A/D converter.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is an analog-to-digital converter (hereinafter referred to as an A/D converter) that converts an analog signal such as a video into a digital signal.
It is related to.

(Prior Art) FIG. 2 shows the configuration of a conventional traveling waveform A/D converter. In the figure, 1 is an analog signal input terminal,
Connected to voltage comparator 2 and delay line 3. Reference voltage source (V
r-r) 4 is connected to the voltage comparator 2, the D/A converter 5, and the D/A converters in the third stage and thereafter. Voltage comparator 2 is connected to flip-flop 6, and flip-flop 6 is connected to D
/A converter 5 and flip-flop 7. D
/A converter 5 is connected to voltage comparator 8;
is also connected to flip-flop 9. delay line 3
is connected to the voltage comparator 8 and the third stage delay line.

Further, the outputs of flip-flops 7 and 9 are connected to the third stage D/A converter and flip-flop. Note that the sampling clock input terminal 10 is connected to all flip-flops.

Next, this operation will be explained. The A/D converter converts an analog signal into a digital data code, and when converting into an n-bit digital data code, up to the nth stage of the circuit shown in FIG. 2 is required. FIG. 2 shows the configuration up to the second stage.

First, the signal voltage applied to the analog signal input terminal 1 and the voltage at 1°t4 are compared by the voltage comparator 2, and this state is stored in the flip-flop 6. That is, the full scale of the analog signal input is taken to be twice vr, 4, and the analog signal input is Vl. , 4, 11'' is written to the flip-flop 6 in synchronization with the sampling clock input terminal 10. Conversely, V, .
, for voltages lower than 4, flip-flop 6 is
O'' is written.The output of flip-flop 6 is the MSB (Most 51gn1fi
cant Bit).

Next, the MSB obtained in the first stage and the digit one below the MSB (MSB-1) are set to "1" and applied to the digital input terminal of the D/A converter 5. 5 to obtain analog signal output. On the other hand, the analog signal input Vra is the voltage comparator 2.
, the flip-flop 6, and the D/A converter 5 by a delay line 3, and the voltage comparator 8 compares this signal with the D/A converter output. This state is stored in flip-flop 9. This is the digit below the MSB of the digital data code (
MSB-1).

The values of the second stage flip-flops 7 and 9 thus obtained become the digital data code of the 2-bit A/D converter. If more bits are needed, the second
By increasing the number of stages shown in the figure, an A/D converter with any bit length can be obtained.

In this way, even in the conventional traveling waveform A/D converter described above, high-speed A/D conversion was possible by using an analog delay line in the delay circuit.

(Problems to be Solved by the Invention) In the conventional A/D conversion described above, it is difficult to miniaturize the delay line.
There was a drawback that it could not be integrated as a /D converter. The object of the invention is to overcome the drawbacks of the prior art and to provide an integrated A/D converter.

(Means for Solving the Problems) The A/D converter of the present invention is a traveling waveform A/D converter consisting of a reference voltage source, a voltage comparator, a flip-flop, a D/A converter, and a delay circuit. , SAW (Surface Acoustic
tic Waves) elements, the conversion time is short and fewer elements are required.
This device is designed to be compact and integrated while retaining the advantages of the /D converter.

(Function) With the above configuration, the present invention can achieve ultra-miniaturization by replacing the delay line with a SAW element, and can integrate a traveling waveform A/D converter.

(Example) An embodiment of the present invention will be described based on FIG.

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

In this figure, the same parts as those in the conventional example shown in FIG. 2 are given the same numbers and their explanations will be omitted.

In FIG. 1, an analog signal input terminal 1 is connected to a voltage comparator 2 and a 5Ail element 11. Reference voltage source (V
rf) 4 is connected to the voltage comparator 2 and the D/A converters in the third and subsequent stages. Voltage comparator 2 is connected to flip-flop 6, flip-flop 6 is connected to D/A converter 5 and flip-flop 7, D/A converter 5 is connected to voltage comparator 8, and voltage comparator 8 is connected to It is also connected to flip-flop 9. The SAW element 11 is connected to the voltage comparator 8 and the third stage 5AIII element. The outputs of flip-flops 7 and 9 are also connected to the third stage D-converter and flip-flop. Note that the sampling clock input terminal 10 is connected to all flip-flops.

The operation of the above embodiment is the same as that of the conventional example, so the explanation thereof will be omitted.

The SAW element, which is the key point of the present invention, will be explained.

A traveling waveform A/D converter generally uses sampling clock 1.
It is used at about 00MHz. Therefore, a delay circuit of approximately LOns is required. If this were to be achieved using a delay line, a space of at least 100 mm2 would be required. However, if a SAW element is used, a delay of about 1/3 ns per 1 μm is possible, so a spacing of 30 μm is sufficient to realize an Ions delay circuit.

In this way, compact integration can be achieved by using SAW elements in the delay circuit, which has been the biggest bottleneck when integrating traveling waveform A/D converters.

(Effects of the Invention) According to the present invention, by using a SAW element in the analog delay circuit, which has been a bottleneck in miniaturizing the integration of traveling waveform A/D converters, there is an effect that miniaturization is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an A/D converter according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional A/D converter. 1...Analog signal input terminal, 2,8...Voltage comparator, 3...Delay line, 4...Reference voltage source, 5...D/A converter, 6,7.9・
- Flip-flop, 10... sampling clock input terminal, 11... SAW element. Patent applicant: Matsushita Electric Industrial Co., Ltd. Figure 1

Claims (1)

[Claims] A traveling waveform analog-to-digital converter comprising a reference voltage source, a voltage comparator, a flip-flop, a digital-to-analog converter, and a delay circuit, characterized in that a SAW element is used as the delay circuit.