JPH06303138A - A/d converter - Google Patents

Abstract

PURPOSE:To obtain a changeover device selecting one input signal or a difference between two input signals for the A/D converter and selecting an input voltage range by providing an input buffer circuit whose gain and an amplifier circuit are selected externally to the A/D converter. CONSTITUTION:When terminals 11, 12 are connected externally, an input buffer circuit 1 acts as an inverting amplifier circuit using an operational amplifier 7 and when terminals 13, 14 are disconnected, a gain of the circuit 1 is set to be 1. On the other hand, when the terminals 13, 14 are connected, the gain of the circuit 1 is set to be 2. When the terminals 11, 12 are disconnected and the terminals 13, 14 are connected externally, the circuit 1 acts as a differential amplifier circuit employing the operational amplifier 7 and its gain is set to be 1 and a signal being the subtraction of the input signal to the terminal 11 from the input signal to the terminal 10 is an input signal to the A/D converter. Thus, the input voltage range and the input signal are switched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an A / D converter capable of changing an input signal and a voltage range of the input signal.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of a conventional A / D converter capable of switching an input voltage range. In the figure, 15
Is an input buffer circuit, 16 is a first resistor, 17 is a second resistor
Resistor, 18 is a third resistor, 19 is a fourth resistor,
20 is an operational amplifier, 21 is an S & H circuit, and 22 is A
A / D conversion circuit, 23 is a first input terminal, and 24 is a second input terminal.

In the conventional A / D converter, the resistance value of the first resistor 16 is R1, and the resistance value of the second resistor 17 is R.
2, when the resistance value of the third resistor 18 is R3 and a signal is input to the first input terminal 23, the gain of the input buffer circuit 15 is R1 / (R2 + R3), and the signal is input to the second input terminal 24. When is input, the gain of the input buffer circuit 15 becomes R1 / R3.

The input voltage range to the second input terminal 23 is
Assuming A to A, the input voltage range to the first input terminal 24 is -A * R3 / (R2 + R3) to A * R3 / (R2 + R).
3). In this way, the input voltage range is switched by switching the input terminal and switching the gain of the input buffer circuit.

[0005]

In the above A / D converter, the input voltage range can be switched, but the input signal can handle only one input signal with reference to the ground. The present invention relates to an A / D converter whose input voltage range is switched and which is switched between one that uses one input signal with respect to ground as an input signal and one that uses the difference between two input signals as an input signal. Further, it is an object of the present invention to obtain an A / D converter capable of simultaneously A / D converting the input signal and eight or less signals having different input voltage ranges.

[0006]

The A / D converter according to the present invention is provided with an input buffer circuit whose gain and amplifier circuits can be switched externally.

Further, this input buffer circuit, eight S & H circuits, a multiplexer circuit for switching signals, and a register for storing eight converted signals are provided.

[0008]

The input voltage range is switched by externally switching the gain of the input buffer circuit, and the input signal is switched by externally switching the amplifier circuit of the input buffer circuit.

Further, by providing an input buffer circuit, eight S & H circuits, and a multiplexer circuit, eight or less signals having different input voltage ranges and input signals can be A / S simultaneously.
D-convert.

[0010]

EXAMPLES Example 1. FIG. 1 shows a block diagram of an embodiment according to the present invention. In the figure, 1 is an input buffer circuit, 2
Is a first resistor, 3 is a second resistor, 4 is a third resistor, 5 is a fourth resistor, 6 is a fifth resistor and all resistance values are R, 7 is an operational amplifier, 8 Is an S & H circuit, 9 is an A / D conversion circuit, 10 is a first terminal, 11 is a second input terminal, 1
2 is a third terminal, 13 is a fourth terminal, and 14 is a fifth terminal.

In FIG. 1, when the second terminal 11 and the third terminal 12 are externally connected, the input buffer circuit 1 becomes an inverting amplifier circuit by the operational amplifier 7, and the fourth terminal 13 and the fifth terminal 14 are connected. The gain of the input buffer circuit 1 changes depending on whether it is released or not. When the fourth terminal 13 and the fifth terminal 14 are separated, the gain of the input buffer circuit 1 is 1, and when the fourth terminal 13 and the fifth terminal 14 are connected, the gain of the input buffer circuit 1 is 2 Becomes

When the input voltage range to the input terminal 10 when the fourth terminal 13 and the fifth terminal 14 are separated is -A to A, when the fourth terminal 13 and the fifth terminal 14 are connected to each other. The input voltage range of is -2 × A to 2 × A.

When the second terminal 11 and the third terminal 12 are separated and the fourth terminal 13 and the fifth terminal 14 are externally connected, the input buffer circuit 1 is an operational amplifier circuit by the operational amplifier 7 and the gain is 1. , Which is obtained by subtracting the input signal to the second terminal 11 from the input signal to the first terminal 10 is A /
It becomes the input signal of the D converter. By connecting the terminals externally as described above, the input voltage range and the input signal can be switched.

Example 2. FIG. 3 is a diagram in which the number of the input buffers 1 in FIG. 1 is increased. 25 is an input buffer circuit, 26 is an S & H circuit, 27 is a multiplexer, 28 is an A / D converter, and 29 registers.

In FIG. 3, eight signals having different voltage ranges and input signals pass through the input buffer circuit 25 and the S & H circuit 2
Enter 6 The S & H circuit 26 simultaneously samples and holds all input signals. This output is input to the multiplexer 27 and output in a time division manner for A / D conversion. The register stores and outputs the eight converted output data.
By providing eight input buffer circuits as described above, eight or less signals having different input voltage ranges and input signals are simultaneously A / D converted.

[0016]

As described above, according to the present invention, the input buffer circuit is provided with the terminals, and the input voltage range can be selected from two types.
(EN) An A / D conversion device capable of selecting an input signal using one input signal and one using a difference between two input signals.

Further, by providing eight input buffer circuits and eight S & H circuits and a register, an A / D converter capable of simultaneously A / D converting eight or less signals having different input voltage ranges and input methods is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 A / A that can change the conventional input voltage range
It is the figure which showed the structure of the D converter.

FIG. 3 is a diagram showing a configuration of a second embodiment of the present invention.

[Explanation of symbols]

 1 Input buffer circuit 2 1st resistor 3 2nd resistor 4 3rd resistor 5 4th resistor 6 5th resistor 8 S & H circuit 9 A / D conversion circuit 10 1st terminal 11 1st 2 terminal 12 3rd terminal 13 4th terminal 14 5th terminal 26 multiplexer 28 register

Claims (2)

[Claims] 1. A first terminal for receiving an input signal,
A first resistor for receiving a signal in the subsequent stage, a second terminal for inputting a signal for taking the difference between the signal input from the first terminal, and a second terminal for receiving the signal in the subsequent stage Resistor, a third terminal for determining the ground of signals from the first terminal and the second terminal, and a third terminal for eliminating the offset voltage between the second terminal and the third terminal. A third resistor provided between the terminal and the second resistor, and a third resistor provided after the first resistor for amplifying signals from the first terminal and the second terminal. The fourth resistor and the fifth resistor, the fourth terminal which is output to the outside after the fourth resistor to determine the amplification degree, and the amplification degree are determined in the same manner as the fourth terminal. An input buffer circuit having a fifth terminal for outputting to the outside after the fifth resistor, and its output S to perform the sampling and hold &
An A / D conversion device having an H (Sample & Hold) circuit and an A / D conversion circuit. 2. The eight input buffer circuits for receiving up to eight signals having different input voltage ranges and input signals,
S & for simultaneous A / D conversion of 8 or less signals
The A / D conversion device according to claim 1, comprising eight H circuits, a multiplexer circuit, and a register for storing conversion data.