JPH04297129A - Digital/analog conversion circuit - Google Patents

Abstract

PURPOSE:To easily perform operation tests on a board of the D/A conversion circuit incorporating D/A converter on a semiconductor substrate. CONSTITUTION:On the semiconductor substrate of an D/A converter 2, a storage means 4 storing test digital signals corresponding to a reference analog signal, a means 5 outputting test digital signals from the storage means synchronizing with the operation of the D/A converter, and a means 102 selecting the input of the D/A converter, are provided. The output of the D/A converter when the test data is inputted from the storage means is compared and collated with the reference signal.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is a digital-to-analog (digital-to-analog) device that converts digital signals into analog signals on a semiconductor substrate.
Regarding a D/A conversion circuit device equipped with a D/A) converter,
In particular, it relates to the configuration related to the operation test.

0002

[Prior Art] Fig. 3 shows a conventional LS
(Nikkei Electronics 1983)
(June 20th issue, p. 125). In the figure, 301 is a circuit under test (LSI), 302 is a memory for storing test vectors, 303 is a determination circuit, and 304 is a logic (failure) simulator. For testing, a test vector specific to the circuit under test and a corresponding response vector are created in advance using a logic simulator or by hand, and the prepared test vector is input into the circuit to see if the correct response vector comes out. This is done by determining whether the circuit is good or bad. Similarly, in the case of D/A converters, circuit evaluations such as operation tests have been performed by inputting digital signals using a tester or the like.

0003

However, in a D/A converter that includes an analog circuit in its circuit, variations in the individual elements constituting the analog circuit tend to have a large effect on the performance of the circuit. In particular, this trend is becoming more pronounced due to improvements in the performance of D/A conversion circuits and higher speeds due to the adoption of oversampling circuits as a result of recent improvements in semiconductor integration technology. In addition, the test results are often influenced by the test environment such as the wiring of the measurement system and the performance of external elements, or by test equipment such as testers and test jigs. As the performance of circuits improves, even basic operational tests and other evaluations are becoming difficult to perform.

[0004] An object of the present invention is to provide a D/A conversion circuit device that allows operation tests to be easily performed on a board.

[0005]

[Means for Solving the Problems] The present invention provides a memory means for storing a test digital signal corresponding to a reference analog signal on a semiconductor substrate on which a D/A converter is mounted, and a D/A converter. A means for outputting a test digital signal from the storage means in synchronization with the operation of the converter, and a selection of whether to input an external digital signal or a digital signal from the storage means as an input to the D/A converter. It is equipped with a means to do so.

[0006]

[Operation] A reference digital signal for testing is stored, and the digital signal is read out from a storage means such as a ROM in synchronization with the operating clock of a D/A converter, for example.
The signal is input to a D/A converter and converted into an analog signal. By comparing the analog signal output at this time with a predetermined reference signal, evaluations such as basic operation tests can be easily performed. As the number of wiring and external elements in the measurement system is reduced, it is less susceptible to external influences such as the test environment, test equipment, and test jigs.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a D/A conversion circuit device showing an embodiment of the present invention. In the figure, 1 is a D/A conversion circuit device configured on one semiconductor substrate, 2 is a D/A converter that converts a digital signal into an analog signal,
3 is a filter, 4 is a data ROM that stores a reference digital signal for testing, 5 is an address section that generates an address for the data ROM 4, 6 is a digital data bus, 7 is a clock signal line, and 8 is a D/ROM. A converter output line, 9 is an address bus, 101 is an external digital data input terminal, 102 is a digital data input selection terminal, 103 is an analog signal output terminal, 104 is a reset signal input terminal, and 105 is a clock input terminal. .

Next, the test method will be explained. The D/A conversion circuit device 1 of this embodiment has an input selection terminal 102
The digital data input to the D/A converter 2 can be switched by the signal from the D/A converter 2. To select a digital signal stored in the built-in ROM 4, this input selection terminal 102 is set to high level (H). When the reset is released in this state, the ROM 4 stores the digital data in the area designated by the address signals sequentially output from the address generation circuit 5 in synchronization with the operation clock from the terminal 105 until it is reset again. /A converter 2
continues to output. Therefore, the terminal 10 is
Based on the analog output obtained in step 3, it is possible to evaluate whether or not normal operation is being performed.

Note that the ROM 4 and the address generating section 5 have a function to test themselves from the outside, although not described in detail here.

Next, in order to input a digital signal from the outside using a tester or the like, the input selection terminal 102 is set to a low level (
L).

Another embodiment of the invention is shown in FIG. Figure 1
The same reference numerals indicate the same or corresponding parts, but in this embodiment, by adding the clock generation circuit 10, a unique clock signal is created and used based on the clock signal from the original clock input terminal 107. be able to. 10
8 is an original operating clock input terminal corresponding to the terminal 105 in FIG.

In this embodiment, an output terminal 106 is also provided so that the output of the D/A converter 2 can be directly output. As a result, D/A converter 2 and filter 3
It is possible to test both.

[0013]

[Effects of the Invention] As described above, according to the present invention, the D/A
On the same semiconductor substrate as the converter, there is a storage means that stores a test digital signal corresponding to a reference analog signal, and a test digital signal is stored from the storage means in synchronization with the operation of the D/A converter. The digital data from the storage means can be used by providing a means for outputting the data and a means for selecting whether to input a digital signal from the outside or a digital signal from the storage means as an input to the D/A converter. Unlike when inputting a digital signal from an external source, there is no need to perform separate operations to synchronize with the signal input, and D/A can be performed on the board without using a tester.
The basic operation test of the conversion circuit can be easily performed and the efficiency of the operation test can be improved. In addition, during testing, it is only necessary to add a power supply, clock, etc. from the outside, which reduces the number of wiring and external elements in the measurement system, and makes it less susceptible to external influences such as the test environment, test equipment, and test jigs. Accurate performance evaluation becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a D/A conversion circuit device showing one embodiment of the present invention.

FIG. 2 is a block diagram of a D/A conversion circuit device showing another embodiment of the invention.

FIG. 3 is a block diagram showing a conventional LSI testing method.

[Explanation of symbols]

1 D/A conversion circuit device 2 D/A converter 4 Data ROM 5 Address generation circuit 10 Clock generation circuit

Claims (1)

[Claims] Claim 1: A digital-to-analog conversion circuit device equipped with a digital-to-analog converter for converting an externally input digital signal into an analog signal on a semiconductor substrate, in which a reference analog signal is supported on the same semiconductor substrate. a storage means that stores a test digital signal, a means for outputting a test digital signal from the storage means in synchronization with the operation of the digital-to-analog converter, and a means for outputting a test digital signal from the outside as an input to the digital-to-analog converter. or means for selecting which of the digital signals from the storage means is input.