eldo_user

Post-Layout Simulation
Eldo Reduction
Eldo Reduction
The Eldo Reduction capabilities enable Eldo to cope with the parasitic networks constraint by
substituting such networks on the fly with approximately equivalent but smaller-sized networks
computed by the TICER reduction engine.
Note
See the TICER reduction engine references [1, 2, 3].
The quality of the approximation is controlled by setting a cut-off frequency and/or an accuracy
tuning parameter. Additionally a maximum delay error and/or a maximum noise error and/or a
cut-off frequency may be used as explained in this chapter.
Not only backannotated circuits can benefit from the savings in computer resources allowed by
the Eldo Reduction, but also some specific circuits. For instance, this is the case for power
distribution networks having large portions of purely resistive networks.
The reduction methods available in Eldo are also, primarily, available in the xCalibre extraction
tool, and it is strongly recommended to activate the reduction of parasitics while performing
extraction with Calibre ® xRC /xL.
Nevertheless, even when the reduction of parasitic networks is performed in the extraction tool
there may be some benefit in performing reduction in Eldo. This is clearly the case when the
parasitics were generated to be valid over a frequency range that far exceeds the signal
frequencies involved in the simulations to be performed. Using its reduction capabilities enables
Eldo to take full benefit of reduction for each simulation individually, while using parasitic
networks valid over a possibly larger range of frequencies. Although this provides a convenient
capability, it remains preferable (and it is recommended) to use different sets of extracted
parasitics corresponding to the various frequency ranges of the simulations to be performed.
The primary advantages of reduction are:
• Results in smaller circuits, thus faster simulations.
• Requires less memory resources (uses less RAM and reduces swap space allocations).
Basic Reduction
The easiest way of activating Eldo Reduction is by using the generic .REDUCE command:
.REDUCE [FREQUENCY=value] [TUNING=FAST|MODERATE|STANDARD|ACCURATE|VHIGH]
The TUNING=FAST setting is more targeted to digital-like circuits. These refer to circuits with
square signals and for which the accuracy on the signals’ amplitude and delay are less stringent
than for pure analog circuits. Other settings should be suitable for simulating circuits with
higher accuracy requirements. You may optionally specify a maximum delay error, noise error,
Eldo® User's Manual, 15.3 403