eldo_user

Examples
Example 27—Monte Carlo Analysis Autostop
• .AC—AC analysis.
• .MC—Monte Carlo analysis.
• .EXTRACT—Extract characteristics from the simulator results.
• .PLOT—Plot simulator results.
Netlist Explanation
.ac dec 1000 1e6 100e6
The above lines indicate that an AC analysis should be performed on the circuit within the
frequency range 1MHz to 100MHz with 1000 steps per decade.
.mc 2000 all nbbins=50 autostop=std_max_conv
The Monte Carlo command specifies 2000 runs as a hard stop. Eldo will add samples until the
autostop condition std_max_conv is met or the 2000 samples limit is reached. Parameter
nbbins=50 is used to obtain better histograms.
.extract ac label=bandwidth 'crossing(vdb(out), -3) / 10e6'
.extract ac label=max_gain max(vm(out))
.extract dc label=ivdd i(vdd)
The above lines extraction the metrics of interest: maximum gain (at overshoot) and 3dB
bandwidth.
.param stdev_confidence=0.95
.param stdev_abs_accuracy=0.00
.param stdev_rel_accuracy=0.05
The above parameters are passed to the mcconv function. The requirement is 5% relative
accuracy, with 95% confidence level.
.extract MC label=std_max_conv
+ mcconv(bandwidth, STD, CONFIDENCE, 50,
+ stdev_confidence, stdev_abs_accuracy, stdev_rel_accuracy)
+ visible=no
This extract is referenced as the austop condition in the .MC command. We look for 5% relative
accuracy on the standard deviation of bandwidth, with 95% confidence level. 50 pilot runs are
used to feed the CONFIDENCE algorithm.
.extract MC label=meanv_bandwidth_MEAN_VALUE
.extract MC label=stdev_bandwidth_CI_95p_INF
+ '(1-stdev_rel_accuracy) * mcstd(bandwidth)'
.extract MC label=stdev_bandwidth_ESTIMATION
.extract MC label=stdev_bandwidth_CI_95p_SUP
+ '(1+stdev_rel_accuracy) * mcstd(bandwidth)'
'mcavg(bandwidth)'
'mcstd(bandwidth)'
Eldo® User's Manual, 15.3 1341