[SI-LIST] max. over/under shoot
- From: "martinos72" <martinos72@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 21 Sep 2012 16:09:02 -0000
Dear ALL,
according to the i.MX51 datasheet the Absolute Maximum Ratings for VI GPIO
voltage range has been defined as VDD+0.3 and -0.5V.
In the IBIS file the sub-parameter "S_overshoot_high" and "S_overshoot_low" are
equal to VDD and 0.
According to the IBIS SPECIFICATIONS (V5.1) the meaning of the two
sub-paramenter are as follow explained:
"The static overshoot subparameters provide the DC voltage values for which the
model is no longer guaranteed to function correctly. Often these voltages are
given as absolute maximum ratings. However, if any lower *_overshoot_high or
higher *_overshoot_low limit for functional specification compliance exists,
that limit should be used."
According with the above statement the max VI range should be VDD-0, with no
over/under shoot at all.
I have found that also keeping nets very short and slow slew-rates, it is very
difficult to keep over and under shoot = 0. And it is also very demanding
having a series termination resistor on every net (not present also in the
evaluation board.)
It'd be different instead having the chance to have a VDD+0.3 and -0.5V for
over/under shoot.
Could you please tell me your opinion about this?
Best Regards,
OSCAR M.
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