JPH06140932A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To relax the effect of a conversion error of an A/D converter circuit and a D/A converter circuit built in the semiconductor integrated circuit and to reduce the man-hour and the component cost for the adjustment. CONSTITUTION:The circuit is provided with an A/D converter circuit 1 A/D- converting an input signal, a reference signal generating circuit 7 outputting an optional value, a difference output circuit 6 calculating a difference between outputs of the reference signal generating circuit 7 and the A/D converter circuit 1, a holding circuit 9 holding the difference output, an adder circuit 2 adding outputs of the A/D converter circuit 1 and the holding circuit 9, an arithmetic operation circuit 3 calculating the output of the adder circuit 2, a changeover circuit 4 selecting an output of the arithmetic operation circuit 3 or an output of the reference signal generating circuit 7, a D/A converter circuit 5 D/A- converting the output of the changeover circuit 4, and a changeover switch 8 selecting either its output or the input signal and inputting the selected signal to the A/D converter circuit 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit,
In particular, the present invention relates to a semiconductor integrated circuit having a function of converting an input analog signal into a digital signal once, performing processing, and then outputting the analog signal again.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor integrated circuit of this type, as shown in a block circuit diagram of FIG. 2, an analog signal 112 input to an input terminal 54 is converted into an n-bit digital signal 1.
A / D conversion circuit 10 for converting into 13; an arithmetic circuit 11 for performing an arithmetic operation of the converted digital signal such as addition, subtraction, multiplication, division, averaging, etc .; Output to the output terminal 55
/ A conversion circuit 12 and these are integrally formed in one semiconductor integrated circuit.

The operation of this circuit will be described with specific values, for example. At this time, the digital value and the analog value are represented by hexadecimal numbers converted into digital values. For example, when the arithmetic circuit 3 is composed of a 4-bit digital signal and the arithmetic circuit 3 is a double multiplier, when the analog signal “4” is input as the input signal 112, the A / D conversion circuit 10 outputs the digital signal. Is converted into a value of “4” and output as a converted signal 113 to the arithmetic circuit 11. As a result of performing twice the calculation in the calculation circuit 11, the output becomes the value of "8", and the calculation signal 1
14 is input to the D / A conversion circuit 12. The D / A conversion circuit 12 converts the value of “8” of the digital signal into the value of “8” of the analog signal and outputs it as the output signal 115 to the outside.

[0004]

In the semiconductor integrated circuit described above, the A / D conversion circuit 10 and the D / A conversion circuit 1 are provided.
When there is a conversion error in 2, there is a problem that the calculation result of the calculation circuit is significantly changed. For example, in the above example, the conversion error of the A / D conversion circuit 10 is −2, D / A
Regarding the case where the conversion error of the conversion circuit 12 is +1, when the value of the input signal 112 is “4”, the conversion signal 113 is “2” due to the conversion error of the A / D conversion circuit 10.
And the output of the arithmetic circuit 11 has a value of "4", and the output signal 115 has a value of "5" due to a conversion error of the D / A conversion circuit 12, and as a result, an accurate value cannot be obtained.

Therefore, in the past, A / D conversion circuits and D / D converters have been used.
In order to reduce the conversion error of the A conversion circuit, an external circuit for adjustment is required independently, which causes a problem of cost of parts and adjustment man-hours. An object of the present invention is to provide a semiconductor integrated circuit in which the internal circuit configuration of the semiconductor integrated circuit is used without using an external circuit and the change in the operation result due to the conversion error of the A / D conversion circuit or the D / A conversion circuit is suppressed. It is in.

[0006]

The present invention provides an A / D conversion circuit for inputting an analog signal and converting it into an n-bit digital signal, and a reference generation circuit for generating an arbitrary value as an n-bit digital signal. A difference output circuit that takes in the digital output of the reference generation circuit and the digital output of the A / D conversion circuit to calculate the difference, a holding circuit that holds the output of the difference output circuit, and the A / D conversion An adder circuit for adding the output of the holding circuit to the digital output of the circuit to output an n-bit digital signal, an arithmetic circuit for taking an output signal of the adder circuit and performing an arbitrary arithmetic operation, an output of the arithmetic circuit and the reference A switching circuit that selects the output of the generation circuit, a D / A conversion circuit that converts the n-bit digital output of this switching circuit into an analog signal and outputs it as an output signal, and this output signal and the circuit A changeover switch for selecting any one of the input signals to be input to the A / D conversion circuit, and operating the changeover switch, the difference output circuit, the holding circuit, and the changeover circuit in synchronization with the control signal. To do.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block circuit diagram of a semiconductor integrated circuit according to an embodiment of the present invention. In the figure, an A / D conversion circuit 1 for inputting an analog signal 111 and converting it into an n-bit digital signal, an operation circuit 3 for taking an input signal 105 and performing an arbitrary operation, and an n-bit digital output 107 are shown. The D / A conversion circuit 5 for converting into the analog signal 102 is mainly configured, and the following circuits are attached to these circuits.

That is, a reference generating circuit 7 for generating an arbitrary value by an n-bit digital signal 109, a digital output 109 of the reference generating circuit 7 and a digital output of the A / D conversion circuit 1 are calculated and a difference is calculated. Difference output circuit 6 and a holding circuit 9 that holds the difference output circuit 6 by the control signal 103.
And an adder circuit 2 for adding the output of the holding circuit 9 to the digital output 104 of the A / D conversion circuit 1 to output an n-bit digital signal, an output of the arithmetic circuit 3 and an output of the reference generation circuit 7. The switching circuit 4 selected by the control signal 103, the input signal 101 and the output signal 102 of the D / A conversion circuit 5 are selected by the control signal 103, and the A / D is selected.
A changeover switch 8 for inputting to the converter 1 is provided. In addition, 51 is an input terminal, 52 is an output terminal, and 53 is a control terminal.

Next, the operation of this embodiment will be described. In normal operation, the control signal 103 is non-active, and the input signal 101 is switched to A / D via the changeover switch 8.
Input to the conversion circuit 1. The A / D conversion circuit 1 converts the input signal 101, which is an analog signal, into an n-bit digital signal and outputs it to the addition circuit 2 and the difference output circuit 6. The adder circuit 2 adds the output signal 110 of the holding circuit 9 to the output signal 104 of the A / D conversion circuit 1 and outputs it to the arithmetic circuit 3. The holding circuit 9 at this time outputs the output signal 110 according to the control signal 103.
Is being held. The arithmetic circuit 3 performs arbitrary arithmetic operations on the input data, such as addition, subtraction, multiplication, division, averaging, etc., and outputs the data to the switching circuit 4. The switching circuit 4 uses the control signal 103
Then, the output signal 106 of the arithmetic circuit 3 is selected and output. The D / A conversion circuit 5 inputs the n-bit digital signal 107 of the switching circuit 4 and converts it into an analog signal to obtain an output signal 102.

Here, the value of the holding circuit 9 is the control signal 1
It is obtained by activating 03, and the operation is as follows. The control circuit 103 causes the switching circuit 4 to generate an n-bit digital signal 109 generated from the reference generation circuit 7.
Is input and output to the D / A conversion circuit 5. The D / A conversion circuit 5 converts the digital signal 109 into an analog signal 102 and outputs it to the outside, and at the same time, is input to the changeover switch 8. With the control signal 103, the changeover switch 8 outputs the output signal 10
2 is selected and input to the A / D conversion circuit 1. The A / D conversion circuit 1 converts the output signal 102, which is an analog signal, into an n-bit digital signal and outputs it to the addition circuit 2 and the difference output circuit 6. The difference output circuit 6 is the output signal 1 of the A / D conversion circuit 1.
04 and the n-bit digital signal 109 of the reference generation circuit 7.
And the difference is output to the holding circuit 9. The holding circuit 9 inputs the output signal 108 of the difference output circuit 6 and outputs the held data when the control signal 103 becomes active.

In this circuit, the operation of inputting a specific value will be described in comparison with the conventional one. As in the case of FIG. 2, the digital value and the analog value are represented by hexadecimal numbers converted into digital values. Further, the conversion error of the A / D conversion circuit 1 is −
2, the conversion error of the D / A conversion circuit 5 is +1 and the arithmetic circuit 3 is a double multiplier.

In this case, when the control signal 103 is activated, the reference generation circuit 7 outputs any value from "0" to "15", here "7", to the output signal 109, and the switching circuit 4 Outputs the value to the output signal 107. The D / A conversion circuit 5 adds “1” to the conversion error when converting the digital signal 107 into the analog signal 102, and is “8”.
Is input to the changeover switch 8. The analog signal 102 input to the A / D conversion circuit 1 via the changeover switch 8 is output as a value of “6” due to conversion error −2 when converted to a digital signal. A / D conversion circuit 1
The converted output 104 is input to the difference output circuit 6 and becomes “+1” when the difference from the output signal 109 of the reference generation circuit 7 is taken,
The output signal 108 is output to the holding circuit 9.

Next, the control signal 103 is made non-active to bring the holding circuit 9 into the holding state. Output signal 1 of holding circuit 9
10 inputs “+1” to the adder circuit 2. Control signal 10
Assuming that a value of "4" is input as the input signal 101 through the changeover switch 8 which is in the normal state by making 3 inactive, the output of the A / D conversion circuit 1 is converted by the conversion error -2. The value "2" is output. The conversion output 104 is the output signal 11 of the holding circuit 9 in the adder circuit 2.
It is added with +1 of 0 to become “3”, which is input to the arithmetic circuit 3, and the value of “6” is output by the doubling operation and is input to the D / A conversion circuit 5 via the switching circuit 4. The D / A conversion circuit 5 outputs the value "7" as the output signal 1 due to the conversion error +1.
It is output as 02. Therefore, in comparison with the conventional example in which the A / D conversion circuit and the D / A conversion circuit include the same conversion error, in the case of the same input signal, the original output value is "8", but "7" in this embodiment. Therefore, it is understood that the error of the calculation result is reduced as compared with the conventional output value "5" shown in FIG.

[0014]

As described above, the present invention is provided with the reference generation circuit, the difference output circuit, the holding circuit, the addition circuit, and the switching circuit, so that the A / D conversion circuit and the D / A conversion circuit are free from conversion errors. Even if it contains, it is possible to suppress the influence of the conversion error. Since these circuits are configured as internal circuits of the semiconductor integrated circuit, it is only necessary to supply a control signal from the outside, an external circuit is not required, cost is reduced, and adjustment man-hours are not required. There is an effect. Further, by activating the control signal when the power is turned on, the error is corrected each time the device is used, and the reliability is improved. Furthermore, D /
By adjusting only the A conversion circuit, more accurate results can be obtained.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an embodiment of a semiconductor integrated circuit of the present invention.

FIG. 2 is a block circuit diagram of an example of a conventional semiconductor integrated circuit.

[Explanation of symbols]

 1 A / D conversion circuit 2 Addition circuit 3 Operation circuit 4 Switching circuit 5 D / A conversion circuit 6 Difference output circuit 7 Reference generation circuit 8 Changeover switch 9 Holding circuit

Claims (1)

[Claims] 1. An A / D conversion circuit for inputting an analog signal and converting it into an n-bit digital signal, a reference generation circuit for generating an arbitrary value as an n-bit digital signal, and a digital output of this reference generation circuit. And a difference output circuit that takes in the digital output of the A / D conversion circuit and calculates the difference, a holding circuit that holds the output of the difference output circuit, and the A / D
An adding circuit for adding the output of the holding circuit to the digital output of the converting circuit to output an n-bit digital signal, an arithmetic circuit for taking an output signal of the adding circuit and performing an arbitrary arithmetic operation, an output of the arithmetic circuit and the above A switching circuit that selects the output of the reference generation circuit, a D / A conversion circuit that converts the n-bit digital output of this switching circuit into an analog signal and outputs it as an output signal, and this output signal and the input that is input to the circuit. A selector switch for selecting one of the signals and inputting it to the A / D conversion circuit, and operating the selector switch, the difference output circuit, the holding circuit, and the selector circuit in synchronization with a control signal. Integrated semiconductor circuit.