串扰问题？

lwenming

请问各位大虾，1、HyperLynx对PCB板做快速串扰分析时，需要加入器件IBIS模型吗？2、在加入IBIS模型之后，串扰的值一般是多大，不影响设计？
我在DXP下面找了个example,对其进行快速串扰分析时，不加如IBIS模型，采用默认的模型参数为
; m6 I, c4 {2 e% NBoard temperature ................ 20.0 degrees C
, X. [' C6 L* [1 I1 U/ ^  Default IC model (used for quick analysis if IC model is missing)
/ z1 U3 @* A2 q' M  e" T    IC driver rise/fall time ..2.000 ns
6 g( f6 ^* ~# N) V; Q+ T    IC driver switching voltage range ..3.00 V
+ K  g" I. Z' o+ M( y    IC driver output impedance 1.0 ohms
    IC input capacitance ..... 7.0 pF
串扰门限为
! {& }" M- }7 o+ O0 GMaximum allowed crosstalk ........... 200 mv peak
) Q* B% }: r2 m- ^4 G, E7 L9 b特定看一个网络：
2 {4 h" `% A* l- t  NET = SOFT_TCK
( A* ~) x  g5 t: C) ?   ELECTRICALLY ASSOCIATED NETS --------------------------------------
     None
( j& k6 E4 R% |( F2 z9 K9 }   AGGRESSOR NETS (Estimated peak crosstalk)
# |& Y* `6 v8 ?1 [1 b  B     NetFPGA1S_B22 .................. 233 mv
& @! Y9 Q% S# U4 c5 l; D     Total estimated crosstalk ....................... 233 mv
     ** Warning ** Estimate exceeds maximum allowed crosstalk!
而我分配模型之后，该网络的串扰增加了很多：
  NET = SOFT_TCK
' l8 D2 c  c) Q; h   ELECTRICALLY ASSOCIATED NETS --------------------------------------
     None
* q* _6 H0 O- V7 n+ i% k$ I   AGGRESSOR NETS (Estimated peak crosstalk)
     NetFPGA1S_B22 ..................1268 mv
     NetFPGA1S_A21 ..................1053 mv
4 ~2 N3 h7 ~* P- N% t. k' A: i     NetFPGA1S_A20 .................. 456 mv
     SOFT_TDI ....................... 319 mv
     DIG5_SEG2 ...................... 227 mv
  |) {- i0 l; s/ B- X  F     Sum of the two strongest aggressors .............2321 mv
     ** Warning ** Estimate exceeds maximum allowed crosstalk!

kiddguan

需要加入模型，阈值一般可以通过简单计算得到.不同的电平，阈值是不同的，5v的10%=500mv,考虑串扰是500mv的30%=150mv；