Hspice在跑tran時，time step的設定與影響？

doc

請問各位前輩...
一般hspice在跑 .tran時，大家會如何選取time step...
& M& L9 P* F7 I  Z, B& e% c會取電路操作頻率的百分之幾？

0 \& p. z+ K- Q* W! c小弟最近在模擬一個IO...
將time step設在0.1n以下，如0.05n或0.01n，模擬結果會產生震盪的現象...
& `1 u$ y; |. l+ joutput waveform會有一個高頻的小震幅上下抖動...
會導致這個模擬結果錯誤，LDO的輸出電壓飄到十幾伏(電壓源也才3.3V)，電流也飄掉...
試了一些option，結果還是一樣...

但把time step設成0.1n...結果就正常...
但又怕time step設不夠細...模擬結果不夠準確...
7 e) }2 o4 ^0 Q
不知道有沒有什麼設定可以避免這個震盪的現象...
/ e1 B: f4 C8 k如果電路操作在5G...time step只是0.1n夠嗎？

hyseresis

How does the value of TSTEP affect my transient simulation?
TSTEP is specified in the transient analysis netlist command.
.TRAN TSTEP1 TSTOP1 TSTEP2 TSTOP2 ... TSTEPN TSTOPN
0 k5 U, z3 p7 e; u% `The most common usage is a single TSTEP/TSTOP pair. For example:
.TRAN 0.1ps 100ns
; b( r+ q- V( f% N, n8 d1 \$ QTSTEP has a variety of effects on the operation of HSPICE.
1. When the RUNLVL algorithm is in use:
  - RUNLVL "in use" is defined as HSPICE version >= 2004.09 and OPTION RUNLVL > 0.
    For HSPICE version >= 2006.09, RUNLVL=3 by default.
- Z- }/ {% o& n  - The minimum timestep is determined by the RUNLVL algorithm. The RMIN option is ignored.
  - The maximum timestep has a "soft" limit of RMAX*TSTEP. The RUNLVL algorithm
" _& Y( r3 C7 c, y; Z% D& Y' ]9 s    allows the timestep to exceed RMAX*TSTEP as long as tighter Newton-Raphson
    tolerances are met (voltage, current, charge).The default value of RMAX is 5.
  - The DELMAX option can be used to override the RUNLVL algorithm's choice of
    maximum timestep. When DELMAX is used, TSTEP has no impact on simulation accuracy (except
' z8 W5 E. H8 L; |2 W4 t* w& B+ f    when used in conjunction with .OPTION INTERP, see #3 below).
2. When RUNLVL=0 (discouraged):
  - The minimum timestep is defined as TSTEP*RMIN. The default value of RMIN is 1e-9.
  - The maximum timestep is defined as TSTEP*RMAX. The default value of RMAX is 5.
  - These limits are "hard" limits.
0 v5 [" |2 @7 A* h2 q) T5 L  - If the simulation engine attempts to choose a timestep < TSTEP*RMIN, a
    Timestep Too Small Error will result.
; D# i+ Z: g: G- v% s0 X  - The simulation engine is never allowed to take a larger timestep than
    TSTEP*RMAX.
Summary
With the introduction of the RUNLVL algorithm, the impact of TSTEP has been
! [& E. V; E3 e$ g6 Pgreatly reduced to the point that it can be ignored except for niche applications
8 P0 i6 _: K  nlike INTERP. One should still be careful not to set TSTEP too small for long,
1 G, }2 b4 @5 Y, mlow frequency simulations in which the soft timestep upper limit of RMAX*TSTEP
& o, J. Q8 T, T  x# f1 Q9 L- ^9 W1 i, \may still force more timestep solutions than is necessary which will cause
3 e! a! B) p8 E' Xexcessive simulation time.

semico_ljj

step 可以是时钟频率的1/5~1/10，这样比较精确！