What does ramp in IBIS file indicate?

[soodv03]

Hi

wat does ramp in IBIS file indicate. For eg .2621/.2597n watdoes it mean...y there r 2 values...plz help

 

[mmirmak]

Re: Ramp in IBIS file

Thanks for asking about IBIS! The [Ramp] keyword refers to the (given) amount of time a driver uses to transition through a (given) voltage range, into a defined load. The values of time and voltage are given explicitly, as a ratio of dV to dt. Separate ratios are given for rising and falling transitions.

For example,

[Ramp]
dV/dt_f 1.8V/0.5n NA NA
dV/dt_f 1.8V/0.6n NA NA
R_load =50

means that, for the typical corner, the buffer will transition through a range of 1.8 V in 0.5 ns for a rising edge driven into a 50 ohm load to ground. The buffer will cover the same voltage range on a falling edge in 0.6 ns for the same load connected to Vcc.

Note that the voltage is 20-80% of the total swing into the given load. In other words, if the example buffer buffer above has a Vcc of 5 V, and its 20-80% swing into the load is 1.8 V, its actual full swing into the load is 3 V or from 5 V down to 2 V. The Ramp voltage is always a 20-80% value.

More information can be found in the IBIS Cookbook: **broken link removed**

I hope this helps!

- Michael Mirmak
Intel Corp.
Chair, EIA IBIS Open Forum