Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2000-07-21
2003-03-18
Sherry, Michael (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S210000, C324S211000
Reexamination Certificate
active
06535011
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a testing device and a testing method for a semiconductor integrated circuit (e.g., a LCD driver IC, etc.) that incorporates a multiple number of D/A converters and outputs voltages from the D/A converters via the associated output terminals as well as a storage medium having the testing program stored therein. In particular, the present invention relates to a testing device, a testing method and a storage medium having the testing program stored therein, which enable very quick and highly precise test of the output voltages from the D/A converters.
(2) Description of the Prior Art
With the development of LCD panels into a high precision configuration, LCD driver LSIs incorporated in LCD panels have become developed to handle a greater number of outputs and a greater number of tones. For such tonal display, each output circuit in the LCD driver LSI incorporates an individual D/A converter to output a tonal voltage. For example, a 6 bit D/A converter can display 64 levels of tones while a 8 bit D/A converter can display 256 levels of tones.
Upon the test for such a LCD driver LSI, it is checked if all the tonal voltage levels output from individual D/A converters fall within respective correct (pass) ranges, as shown in FIG.
1
.
FIG. 2
is a conceptual view illustrating a conventional testing method by using a test example of a LCD driver LSI
51
incorporating ‘m’ outputs.
A semiconductor testing device (tester)
52
is used to supply an input signal to LCD driver LSI
51
so that each incorporated D/A converter (not shown) outputs a voltage level corresponding to the first tonal level. The voltage levels corresponding to the first tonal level are output from associated output terminals (output
1
, . . . , output m) of LCD driver LSI
51
and supplied to input terminals (V) of tester
52
. In tester
52
, matrix switches (not shown) are sequentially turned on and off so that the output voltages corresponding to the first tonal level are sequentially measured from the first output to the m-th output, one by one, using a high accuracy analog voltage measuring device (not shown) incorporated in the tester. The measured results are sequentially stored in an incorporated data memory (not shown). This process is repeated by the number of tonal levels until all pieces of data (m outputs) for all tonal levels (n levels) are stored into the memory. As a result, m×n pieces of data will be stored into the memory. The data stored in this memory is subjected to a series of logical and arithmetical operations through an unillustrated processing unit incorporated in tester
52
so as to check each tonal voltage of each output.
In such a test of a LCD driver LSI
51
, with the development towards a greater number of outputs and a greater number of tones, the amount of data to be picked up and the time required for data processing have increase, so that the testing time increases sharply. Further, increase of the tonal levels in number will make the potential difference between adjacent tonal voltage levels smaller, requiring a greater precision for measuring the voltages of all the tonal levels, which results in a further longer time for testing.
Since, with the thus development towards a greater number of outputs and a greater number of tones, the conventional testing method should handle an increased amount of data and perform very high-accurate voltage measurements for all the tonal output voltages, the testing time has become markedly longer and the test cost has increased sharply.
SUMMARY OF THE INVENTION
The present invention has been completed in view of the above prior art situation, and it is therefore an object of the present invention to provide a testing device, a testing method and a storage medium having the testing program stored therein, which enable very quick and highly precise test of semiconductor integrated circuits.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the first aspect of the present invention, a testing device for a semiconductor integrated circuit which incorporates a multiple number of D/A converters and outputs voltages from the D/A converters via associated output terminals, includes:
a voltage measuring means for measuring the special output voltage corresponding to each tonal level output from a special output terminal of a special D/A converter and computing the difference between the special output voltage and the associated expected voltage as a special differential voltage;
differential amplifying means which, for each tone, receives the special output voltage and output voltages from the output terminals other than the special output terminal and calculates differential voltages and outputs the amplified differential voltages; and
a comparing and determining means for determining whether the amplified differential voltages output from the differential amplifying means fall within a determination voltage range which is specified in accordance with the special differential voltage dependent on each tone.
In accordance with the second aspect of the present invention, the testing device for a semiconductor integrated circuit, having the above first feature is characterized in that the number of differential amplifying means is equal to the number of the output terminals other than the special output terminal, each of the differential amplifying means has an input for receiving a corresponding output voltage output from one of the output terminals other than the special output terminal and another input for receiving the special output voltage in common, and the comparing and determining means effects simultaneous judgement as to all the amplified differential voltages output from the differential amplifying means.
In accordance with the third aspect of the present invention, the testing device for a semiconductor integrated circuit, having the above first or second feature is characterized in that the upper and lower limit voltage values that specify the determination voltage range is set up by shifting the standard upper and lower limit voltage values which are given previously in conformity with the expected voltage value by a fixed value that corresponds to the special differential voltage value.
In accordance with the fourth aspect of the present invention, a testing method for a semiconductor integrated circuit which incorporates a multiple number of D/A converters and outputs voltages from the D/A converters via associated output terminals, includes the steps of:
measuring the special output voltage corresponding to each tonal level output from a special output terminal of a special D/A converter and computing the difference between the special output voltage and the associated expected voltage as a special differential voltage;
for each tone, receiving the special output voltage and output voltages from the output terminals other than the special output terminal, calculating differential voltages and outputting the amplified differential voltages; and
determining whether the amplified differential voltages output from the differential amplifying means fall within a determination voltage range which is specified in accordance with the special differential voltage dependent on each tone.
In accordance with the fifth aspect of the present invention, a testing method for a semiconductor integrated circuit which incorporates a multiple number of D/A converters and outputs voltages from the D/A converters via associated output terminals, includes the steps of:
measuring the special output voltage corresponding to each tonal level output from a special output terminal of a special D/A converter and computing the difference between the special output voltage and the associated expected voltage as a special differential voltage;
for each tone, receiving the special output voltage and output voltages from the output terminals other than the special output terminal, calculating differential voltages and o
Birch & Stewart Kolasch & Birch, LLP
Nguyen Trung
Sharp Kabushiki Kaisha
Sherry Michael
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