Raghunathan R wrote:
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"Since those 8.5V peaks / dive to 3V and then to 5v happened within 3.5ns, I dont think your SmartCard would not have come to any grief, even if you had left it at that."

Well, I'm not too sure about that. There are smartcards out there that are susceptible to this kind of thing, to the extent that very short (nanosecond), high voltage pulses are used in security attacks.

"OK having seen that with the sampling scope, could you manage to knock out the swing and dive from the clock pulse ?"

Oh yes, that was quite simple. A 47Ω resistor in series with the output did the trick.

"The issue of a "CLEAN" clock pulse is inversely proportional to the sophistication level of intrumentation deployed to monitor it. Higher the level, lesser the CLEAN !"

Absolutely :o)

The point is, though, that todays high-speed logic IC's can take you by surprise. I had never imagined that a 3 cm. PCB trace could have such a dramatic effect!


Rob.