UIC option in SPICE?

[billcalley]

I have read all I could find about the Use Initial Conditions (UIC)
option in SPICE, but I still don't fully understand it. The reason I
am confused is this: When I run a DC transient analysis with UIC
enabled on a simple RLC tank circuit (with all passives having an IC of
'0'), shouldn't these results be the same as a DC transient
simulation with *no* UIC, since they should both have a initial
starting condition of 0V/0A? Yet with the simulation with no UIC
enabled, the circuit reaches steady state instantly; while with the UIC
option enabled it takes a finite time to reach its voltage level, then
over/undershoots a few time (rings) -- as it should. What am I missing
here?

Thank You,

-Bill

 

[billcalley]

Thanks very much for the clear answer Jonathan! Very much appreciated.

Best Regards,

-Bill