JPH0244817A - Sequential comparison analog/digital converter - Google Patents

Abstract

PURPOSE:To facilitate the estimation of a fault part by switching a data output terminal in such e way that it functions as an input terminal by means of a signal inputted from an external control terminal, converting an external test signal inputted from the data output terminal into the output of a sequential comparison register and supplying it to a D/A converter. CONSTITUTION:When a check mode is switched by the external control terminal 5, a check mode switching control circuit 7 causes a data output pin 8 which has been an output pin till that time to function as an input pin, and the external test signal can be inputted. Consequently, the check mode switching control circuit 7 converts the external test signal into the output of the sequential comparison register 3, and supplies the external test signal inputted from the data output pin 8 to the D/A converter. With optionally inputting the external test signal, a D/A monitor output terminal 6 removes and checks an objective voltage. Thus, the fault can easily be analyzed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a successive approximation analog-to-digital converter.

[Conventional technology]

FIG. 2 shows a configuration diagram of a conventional successive approximation analog-to-digital converter (hereinafter analog-to-digital is referred to as D/A).

In FIG. 2, 9 is a comparator that compares the output of the D/A converter 12 and the analog input voltage, 10 is a control circuit that controls the successive approximation register 11 based on the judgment of the comparator 9, and 11 is a control circuit that controls the D/A converter. 12 is a D/A converter that receives the instruction of the successive approximation register and generates a reference comparison voltage.

When an analog input voltage is input, a reference voltage for this is output from the D/A converter 12 and the comparator 9
are compared. In response to the determination, the control circuit 10
The successive approximation register 11 is controlled so that the next comparison voltage of the A converter 12 can be generated. Successive approximation register 11 receives instructions from control circuit 10 and controls D/A converter 12 . These series of operations are repeated to determine the A/D value in order from the most significant bits.

[Problem to be solved by the invention]

The conventional A/D converter described above includes the D/A converter 12.
Since it is not possible to check the fault, it takes a lot of time during failure analysis, it is difficult to estimate the failure location, and there are few means for investigating from the outside.

An object of the present invention is to provide an A/D converter that can solve the above-mentioned drawbacks, shorten analysis time, and increase the means for external investigation to facilitate estimation of failure locations. It is in.

[Means to solve the problem]

The successive approximation analog-to-digital converter of the present invention includes a D/A converter that generates an internal reference voltage, a comparator that compares an external analog input signal and the output of the D/A converter, and a determination result of the comparator. A successive approximation register that controls the D/A converter based on the data output terminal, an external control terminal, and a signal input from the external control terminal, switches the data output terminal to function as an input terminal, and inputs from the data output terminal. The D/A converts the external test signal into the output of the successive approximation register.
The present invention is characterized by having a check mode switching control circuit that supplies power to the converter.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

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

In FIG. 1, 1 is a comparator that compares the analog input voltage and the output of the D/A converter 4, 2 is a control circuit that controls the successive approximation register 3 based on the judgment of the comparator 1, and 3 is the D/A converter 4. 4 is a D/A converter that receives the command of successive approximation register 3 and generates a reference comparison voltage, 5 is an external control terminal that enables check mode switching, and 6 is the output of the D/A converter. 7 is a check mode switching control circuit that receives commands input from the external control terminal 5 to switch the check mode, and 8 is an A/D monitor output terminal for monitoring the A/D.
This is a data output pin that outputs the converted value.

The A/D conversion operation itself is the same as that in the conventional A/D converter described above, but when the check mode is switched by the external control terminal 5, the check mode switching control circuit 17 changes the output pin that was previously used. The data output pin 8 now functions as an input pin, allowing input of an external test signal. As a result, the check mode switching control circuit 7 supplies the external test signal input from the data output pin 8 to the D/A converter 4 instead of the output of the successive approximation register 3 during normal operation.

Next, by inputting an external test signal arbitrarily, the D/
A desired voltage can be taken out and checked using the A monitor output terminal. By doing so, it becomes possible to facilitate failure analysis without spending much time during failure analysis, and to increase the number of external investigation means.

〔Effect of the invention〕

As is clear from the above description, according to the A/D converter of the present invention, the output of the internal D/A converter can be controlled from the outside and taken out to the outside through the monitor terminal, and the output of the internal D/A
This not only makes it easier to check the A converter, but also reduces the analysis time during failure analysis, makes it easier to estimate the failure location, and increases the number of external investigation means.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention, and FIG. 2 is a conventional circuit configuration diagram. 1.9... Comparator, 2,10... Control circuit,
2.11...Successive approximation register, 4,12...D/
A converter, 5...external control terminal, 6...D/A
Monitor output terminal, 7... Check mode switching control circuit, 8... Data output pin.

Claims (1)

[Claims] A D/A converter that generates an internal reference voltage, a comparator that compares an external analog input signal with the output of the D/A converter, and a sequential controller that controls the D/A converter based on the determination result of the comparator. A data output terminal is switched to function as an input terminal by a comparison register, an external control terminal, and a signal input from the external control terminal, and an external test signal input from the data output terminal is outputted from the successive approximation register. Instead, the above D
1. A successive approximation analog-to-digital converter comprising a check mode switching control circuit for supplying a signal to an A/A converter.