|
Tech
Scan
Let’s face signal integrity problems
head-on
Craig Overhage
We humans have an amazing capacity to avoid unpleasant
realities. We carry on in ignorant bliss, either truly
unenlightened about a coming disaster or, like the three
monkeys, pretending that nothing bad will happen if
we neither see, nor hear nor speak any evil.
We humans have an amazing capacity to avoid unpleasant
realities. We carry on in ignorant bliss, either truly
unenlightened about a coming disaster or, like the three
monkeys, pretending that nothing bad will happen if
we neither see, nor hear nor speak any evil.
Being human, we in the electronics industry are naturally
also affected by this deadly tendency to avoid the truth,
even when it’s staring us straight in the eyes.
If you’re looking for evidence, you need go no
further than the computer industry’s recent painful
lessons with signal integrity problems. As clock speeds
begin to outstrip the printed circuit board’s ability
to transmit signals in the bus, we have seen a growing
number of near misses and some outright flaming crashes,
including project delays, missed market windows and
even product recalls.
As painful as these experiences have been, it’s
shocking to see how many people outside the confines
of the computer industry continue to ignore the warning
signs. It’s time to wake up. Regardless of where
you find yourself in the electronics industry, if you’re
doing high-speed digital design, you’d better be
paying attention to signal integrity.
Signal integrity wasn’t always such an issue. Until
about 10 years ago, gates switched so slowly and stayed
settled for so long that for the most part digital signals
between ICs behaved like nice little ones and zeros.
Those days are long gone. With ever-faster logic edges
and shrinking bus cycle times combined with the underlying
interconnect technology in the PCB staying largely the
same, the result is signal integrity problems.
It will get worse, too. As system speeds continue to
increase, we are likely to see more problems like glitches,
cross talk, jitter, ground bounce and power supply noise
rearing their ugly heads more and more in the future.
(The author is Vice President and General Manager, Instrumentation
Business Unit, Tektronix)
|
