eldo_user

Figure 17-3. Output Buffer Model Building Blocks
IBIS Models Support in Eldo
Buffers
IBIS provides two ways for defining the switching characteristics:
• If the output switching (V-T) waveform of a buffer can be approximated by a linear
ramp then the V-T data may be reported as a rising and falling ramp rate (dV/dt) by
using the [Ramp] keyword.
• Using the [Rising Waveform] and [Falling Waveform] keywords if the output switching
waveform of the buffer is significantly non-linear.
In both cases the transient current is considered to be a factor from the DC (steady state) current
and this factor is calculated from the provided switching data. There are two factors; k_pullup
and k_pulldown. These factors range from 0, representing a switched off pull-up/pull-down
network, to 1, representing a fully switched on network. The switching starts when d_drive
crosses 0.5 V and according to the buffer polarity, inverting or non-inverting, the appropriate
network is switched on or off.
Output_ECL buffer differs from Output buffer in that the a_pdref is internally connected to the
a_puref; that is, pull-up and pull-down share the same power reference. Output and
Output_ECL buffers also differ in the conventions related to the [Pulldown], [Temperature
Range], [Pin Mapping] keywords and the measuring conditions of the switching characteristics.
Eldo® User's Manual, 15.3 737