eldo_user

Notes
Eldo Netlist Setup
Arithmetic Functions
• Where VAL is defined in the previous tables, it normally means a numeric value, but in
certain cases, the functions may also be applied to waves.
• The MAX and MIN functions are automatically converted into DMAX and DMIN
functions when necessary, for example: R1 1 2 {min(2,1,5)} is equivalent to: R1 1 2
{dmin(2,1,5)} which is also equivalent to: R1 1 2 1
There is no limit to the number of arguments that can be used in MAX, MIN, DMAX
and DMIN arguments.
• If three arguments are specified for MIN (that is, MIN(a,b,c)), this represents the MIN of
waveform a in the time window [b,c]. Use DMIN to return the minimum of a, b and c as
computed at each time step.
• The MIN/MAX/ABS/SGN/SIGN functions, when used in bias-dependent expression
(such as in R(V)), can cause non-convergence due to these operators making the
function non-derivable. Use option MMSMOOTH to make them derivable, to avoid
such problems. Alternatively use the SMMIN, SMMAX, SMABS, SMSGN and
SMSIGN operators.
• DDT(VAL) and IDT(VAL) can only be used on E & G elements, see the corresponding
descriptions for the Voltage Controlled Voltage Source and Voltage Controlled Current
Source. Expressions associated with R/L/C devices do not support DDT/IDT
operators.The DDT operator differs from the DERIV operator in the sense that DDT
utilizes the integration scheme used by Eldo, while the DERIV operator exclusively uses
the Backward-Euler algorithm.
• There can be differences between the DERIV operator of Eldo and the equivalent
operator (DRV) of EZwave. The formula used for the Eldo DERIV operator is
Backward-Euler (that is, deriv(f(t)) = (f(t) - f(t-h))/h) with t being the current time and h
being the time step, however the DRV operator of EZwave uses a more complex
formula based on f(t), f(t-h) and f(t+h). Eldo cannot use the EZwave “post-processor”
formulation, because it requires to know the value at t+h, which is not possible when the
simulator is running (Eldo at time t cannot know the value at t+h), but post-processor
formulation is usually smoother, hence both formulations are used.
• Nested COMPLEX() statements are forbidden, as well as using complex quantities for
the real or imaginary part. Corresponding errors are:
ERROR 3040: Nested complex(,) functions is not allowed.
ERROR 3041: Complex quantities can not be used inside complex(,)
function.
• If CEIL, ROUND, FLOOR cause convergence problems, Eldo will generate a warning
and invite the user to specify option NOLTEDISC to bypass LTE checks.
Eldo® User's Manual, 15.3 113