JPH05167448A - A/d converter - Google Patents

Abstract

PURPOSE:To allow the A/D converter to cope with a case that the conversion speed takes precedence over the resolution and the conversion processing is desired to be executed at a high speed or a case that the resolution takes precedence over the conversion speed and the conversion accuracy is enhanced by making the resolution for A/D conversion variable. CONSTITUTION:A control circuit 2 controls a ladder resistor 5 and a switch tree 4 based on data of a resolution register 1 representing the designated resolution. A reference voltage representing a change number of times in response to the resolution designated by a comparator 6 is given and compared with a voltage of an input analog signal and the result of comparison is stored in a register 3 as a converted digital signal. When the resolution is high, number of times of change in the reference voltage is large and the conversion accuracy is enhanced. When the resolution is low, number of times of change in the reference voltage is less, the conversion accuracy is low but the conversion processing time is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog-to-digital converter incorporated in a microcomputer or the like and converting an input analog signal into a digital signal, and more particularly to control of resolution of analog-to-digital conversion.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a configuration of a conventional analog-digital conversion device. In FIG. 2, 6 is a comparator for comparing the magnitude of an analog signal input from an input port (not shown) and the reference voltage, 3 is a register for storing the comparison result of the comparator 6 as a digital signal, and 5 is a supply voltage ( A ladder resistor (division resistor) 4 for dividing a voltage due to the potential difference between the power supply voltage and the reference voltage into a predetermined voltage gives a divided voltage divided by the ladder resistor 5 as a reference voltage to the comparator 6 according to the output of the register 3. Switch tree (reference voltage supply means),
A control circuit 2 controls the register 3 and the comparator 6. The power supply voltage is 0V when grounded.

Next, the operation will be described. The voltage of the analog signal input from the input port or the like is compared in magnitude with the reference voltage in the comparator 6, and the comparison result is stored in the register 3 as a digital signal. Since the reference voltage successively compares the voltage of the input analog signal,
The voltage level changes constantly. The ladder resistor 5 divides the supply voltage into a predetermined voltage, and this divided voltage is applied to the register 3
Is selected by a switch tree 4 controlled by the output of the comparator and applied to a comparator 6 as a reference voltage. The supply voltage is divided into 256 according to the number of bits of a predetermined resolution (the number of bits based on the conversion value of the present analog-digital conversion device), for example, in the case of 8 bits, and the voltage value of the input analog signal is divided into 256 (reference voltage). Is a voltage for comparing with and converting to a digital value. The analog signal input to the comparator 6, which is compared using such a reference voltage, is converted into a digital signal.

[0004]

In the conventional analog-digital converter, the supply voltage is, for example, 25 as described above.
Since it is divided into 6 and given to the comparator as a reference voltage, and the voltage of the input analog signal is compared and converted into a digital signal, the resolution of analog-digital conversion is constant and the analog-digital conversion time requires a certain time. Therefore, there is a problem that it cannot be dealt with when it is desired to prioritize the conversion speed over the resolution of the analog-digital conversion to execute the conversion process at a high speed, or to prioritize the resolution over the conversion speed to improve the conversion accuracy. It was

The present invention has been made to solve the above problems, and an object of the present invention is to provide an analog-digital conversion device capable of varying the resolution of analog-digital conversion.

[0006]

An analog-to-digital converter according to the present invention includes a resolution register 1 for storing data indicating a specified resolution of analog-to-digital conversion, and a dividing resistor (based on the data in the resolution register 1 ( The control circuit 2 controls the ladder resistance 5) and the reference voltage supply means (switch tree 4) to change the reference voltage to the comparator 6.

[0007]

The control circuit 2 controls the dividing resistor (ladder resistor 5) and the reference voltage supply means (switch tree 4) based on the data of the resolution register 1 indicating the designated resolution. As a result, the reference voltage having the number of changes according to the designated resolution is applied to the comparator 6. That is, if the resolution is high, the number of changes in the reference voltage is large and the digital conversion accuracy of the input analog signal is high, and if the resolution is low, the number of changes in the reference voltage is small and the analog-digital conversion accuracy is low. However, the conversion processing time becomes short.

[0008]

1 is a block diagram showing the configuration of an analog-to-digital converter according to an embodiment of the present invention. In FIG. 1, components corresponding to those shown in FIG. 2 are designated by the same reference numerals, and their description will be omitted. In FIG. 1, reference numeral 1 is a resolution register for storing data indicating the designated resolution of analog-digital conversion. The control circuit 2 of this embodiment uses the data of the resolution register 1 (specified resolution).
According to the above, the switch tree 4 and the ladder resistor 5 are controlled to change the reference voltage to the comparator 6. Further, the switch tree 4 and the ladder resistor 5 in this embodiment are a variable switch tree and a variable ladder resistor having a configuration in which the number of changes of the reference voltage can be changed with the change of the resolution.

Next, the operation will be described. First, the resolution is specified for the resolution register 1 and the data is stored. The voltage of the analog signal input from an input port or the like (not shown) is compared with the reference voltage in the comparator 6, and the reference voltage is set by the control of the control circuit 2. That is, the control circuit 2 controls the switch tree 4 and the ladder resistor 5 according to the data of the resolution register 1 indicating the designated resolution, and controls the voltage supplied to the ladder resistor 5 (the voltage due to the potential difference between the power supply voltage and the reference voltage). The voltage is divided, and this divided voltage is given to the comparator 6 as a reference voltage for the comparator 6.

Here, when it is desired to prioritize the conversion speed over the resolution of the analog-digital conversion and execute the conversion processing at a high speed, a low resolution that does not adversely affect the processing is set in the resolution register 1 and at this time. The control circuit 2 is operated according to the resolution and a reference voltage is given to the comparator 6. The comparator 6 compares the input analog signal voltage with the reference voltage and stores the comparison result in the register 3 as a converted digital signal. Therefore, in this case, the number of changes in the reference voltage is small and the resolution of the analog-digital conversion is inferior, but the conversion speed is high and the conversion processing can be executed at high speed.

On the other hand, when it is desired to prioritize the resolution over the conversion speed to improve the conversion accuracy, a high resolution is set in the resolution register 1, the control circuit 2 is operated by the resolution at this time, and the reference voltage is given to the comparator 6. , Converts input analog signal to digital signal. Therefore, in this case, the conversion speed is slow, but the number of changes in the reference voltage is large and the resolution is high, so that a highly accurate digital signal can be obtained.

By the way, according to the above embodiment, the resolution of the analog-digital conversion can be arbitrarily designated, and depending on the application, when it is desired to lower the resolution and increase the conversion speed, the number of changes in the reference voltage is small, so that the control The number is reduced, and unnecessary processing can be omitted when creating software for controlling.

[0013]

As described above, according to the present invention, the resolution register for storing the data indicating the specified resolution of the analog-digital conversion and the dividing resistor and the reference voltage supply means are controlled based on the data of the resolution register. Since it is configured with a control circuit that changes the reference voltage to the comparator, it is possible to freely set the resolution of analog-digital conversion, which gives priority to analog-digital conversion speed over resolution and conversion processing. It is also possible to deal with the case where it is desired to execute at high speed or when it is desired to prioritize the resolution over the analog-digital conversion speed to improve the analog-digital conversion accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an analog-digital conversion device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional analog-digital conversion device.

[Explanation of symbols]

 1 resolution register 2 control circuit 3 register 4 switch tree (reference voltage supply means) 5 ladder resistance (division resistance) 6 comparator

Claims (1)

[Claims] 1. A comparator for comparing the magnitude of a voltage of an input analog signal and a reference voltage, a register for storing the comparison result of this comparator as a digital signal, and a dividing resistor for dividing a supply voltage into a predetermined voltage. An analog-to-digital conversion device for converting the input analog signal into a digital signal, comprising a reference voltage supply means for applying a divided voltage divided by the dividing resistor as a reference voltage to the comparator according to the output of the register. , A resolution register for storing data indicating a specified resolution of analog-to-digital conversion, and a control circuit for controlling the dividing resistor and the reference voltage supply means based on the data of the resolution register to change the reference voltage to the comparator. An analog-to-digital conversion device characterized in that and are provided.