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Reducing I/O Round-Trip Times 5 DUT Board Performance Considerations

System Reference, January 2001

123

Reducing I/O Round-Trip Times

For bidirectional pins, such as data bus pins, you have to

consider the total I/O round-trip time of the signal from

the I/O Board to the DUT pin and back. This is because at

high vector rates the signal direction changes so often so

that the signals being sent from the tester may collide with

data being sent by the DUT.

As a rule of thumb, you only need to consider the round-

trip time as a potential problem if the switching period of

the I/O pin is less than double the propagation delay of the

signal path (between the tester I/O channel and the DUT

pin).

If you require very fast vector rates in I/O mode, possible

techniques to employ are the use of dual transmission

lines, or the introduction of extra dummy cycles in your

test. You will need to modify your vector files when using

these techniques.

Measures Position/rotate the DUT in the Device Area so as to

shorten the tracks to bidirectional pins (if need be at the

expense of tracks to one-directional pins). This means the

device side where I/O pins are located should be close to

DUT board pogo pin pads. The extra length of tracks

needed for I or O pins will be compensated for by

adjusting pin attribute delay settings or by fixture calibra-

tion.

Specify the use of high-speed DUT board material to the

custom DUT board manufacturer. For instance, teflon is

faster than epoxy.

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AWG G3 PAD FOR PS3 Dokumentacja Strona 123