User`s guide

6 Conver

ence and “Time Step Too Small Errors”

STEPGMIN

An alterative algorithm is GMIN stepping. This is not obtained

by default, and is enabled by specifying the circuit analysis

option STEPGMIN (either using .OPTION STEPGMIN in the

netlist, or by making the appropriate choice from the Analysis/

Setup/Options menu). When enabled, the GMIN stepping

algorithm is applied after the circuit fails to converge with the

power supplies at 100 percent, and if GMIN stepping also fails,

the supplies are then cut back to almost zero.

GMIN stepping attempts to find a solution by starting the

repeating cycle with a large value of GMIN, initially 1.0e10

times the nominal value. If a solution is found at this setting it

then reduces GMIN by a factor of 10, and tries again. This

continues until either GMIN is back to the nominal value, or a

repeating cycle fails to converge. In the latter case, GMIN is

restored to the nominal value and the power supplies are

stepped.