Process parameters

Hello all,

          I have a doubt regarding the method for obtaining the curves
by simulation as outlined in IBIS COOKBOOK. The cookbook says ( under
the section 3.3.1 : "OBTAINING CURVES BY SIMULATION - Simulation
Specifics" ) that :

       "For both the rise/fall time and I-V curve measurements,
        use "typical" process parameters."

        "For CMOS:
        min = min VCC, max temperature, typ process parameters
                                        ---
        max = max VCC, min temperature, typ process parameters"
                                        ---

Later it says that " To account for process variation, decrease the
current values taken at min conditions, increase the current values
taken at max, and derate the rise and fall time values by the
appropriate percentages. "

        This seems to be a roundabout way of doing it. Why can't we
directly use "typ" , "min" , and "max" process parameters, as
appropriate, directly in the simulations ? For example, if SPICE is
used for simulation, we can have three different SPICE models for
transistors, corresponding to the process-variation corners. Why
should "typical" be used in each case ?

Regards,
Vipul K. Singhal
Texas Instruments

 
Received on Wed Jul 16 01:48:48 1997