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COMMENT
The clip positioning function is very useful when devices are close together and when you
have many different size IC's to test. You can put one 20 way clip in the cable and use it on
all IC's up to this size any way around. Even if another supply or ground pin is straddled it will
still correctly orientate the device.
EXERCISE 10 : NO PIN CONNECTION INFORMATION
ACTION
Press STARTon the IC Tester. Observe that most of the pins on the IC have no connections
information showing.
DESCRIPTION
For pins that have no connections information it means that there was a valid logic level seen
on the pins.
COMMENTS
For carrying out the truth table tests it is important to remember that these pins can be
driven high and low by the tester as they are in a normal stable state.
EXERCISE 11 : TRUTH TABLE TEST
ACTION
Press SETUP and note the test types and modes selected. Close the window.
Press START on the IC Tester and observe the analysis window for the test results.
DESCRIPTION
The test Setup indicates that the Truth table test and Connections tests will be carried out.
The Truth Table will check the integrity of the IC giving a functional PASS/ FAIL result. The
circuit conditions will be taken into account prior to the test and the expected truth table
result will be modified accordingly.The test will be carried out in LOOP mode as this is the
best way to show the changing activity around the IC during testing. You will see from the
results that the IC's Truth Table result is a PASS given by the ACTUAL result in the Analysis
box. It is compared to the stored result of the MASTER or good IC test. This shows a good
comparison.
COMMENTS
The Truth Table test verifies the operation of the IC for how it sees it to be wired. It uses
the Connections information to automatically compensate for the circuit conditions giving you
a valid result each individual test in the Loop.
AUTOMATIC CIRCUIT COMPENSATION is a very important part of the IC tester. Its
usefulness can be seen in the next section of TestFLow steps.
Through backdriving, the tester effectively isolates the IC being tested from the influences of
surrounding components. It is important that the PCB be as stable as possible when testing
to reduce the effect of interference from external sources to the DUT. Please view
presentation titled, "ABI Test Methodology" and "Backdriving: The force behind the functional
test" for more detailed information on testing IC's.
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