Re[4]: Ramp Def. ??

Text item:

Ahmed,

I see your point.

I guess, the question is what do you think is the final value. When we wrote
this, we were thinking about the final value under the given test conditions,
which was defined to be a 50 Ohm resistive load. Therefore, the final value is
not a rail-to-rail swing, because the resistor won't let that happen.

Consider a rising edge measurement (for a CMOS device). Before the pullup
begins to drive, the voltage on the output is at GND, because the load resistor
is also connected to GND, so there is no current flowing in the loop. So the
starting voltage of the swing is 0 V. When the pullup is done switching, you
get a voltage division across the pullup and the load resistor. This is your
final value after the transition. Considering the 0 V starting voltage, this
number is also equal to the swing.

I quess, this could have been written up a little more clearly, but we are
engineers, not lawyers. And so far I didn't hear that any one else was confused
by this.

I hope this helps,

Arpad Muranyi
Intel Corporation
================================================================================

Hello Arpad,

Look at the two phrases marked with ***<...>*** in the Usage Rules.
These are (a) and (b) in my original question.

| Usage Rules: The rise and fall time is defined as the time it takes the
| output to go from ***< 20% to 80% of its final value.>***
| The ramp rate is defined as:
|
| dV ***< 20% to 80% voltage swing >***
| -- = ----------------------------------------
| dt Time it takes to swing the above voltage
|

Regards, Ahmed.
|---------------------------------------+------------------------------------|
|Ahmed Omer | Advanced Interconnect Systems Labs |
|E-MAIL: omera@trailblazer.sps.mot.com | Semiconductor Products Sector |
| : R28450@email.sps.mot.com | M O T O R O L A, Inc. |
|Phone: 512-933-2247 | 3501 Ed Bluestein Blvd MDrop: F36
 |
|Fax: 512-933-5845 | Austin, TX 78721 |

|---------------------------------------+------------------------------------|

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Subject: Re: Re[2]: Ramp Def. ??
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