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？
% Z8 a2 ?' q0 K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
Board temperature ................ 20.0 degrees C
  Default IC model (used for quick analysis if IC model is missing)
+ E% W* l3 O/ K- W( m9 t, k    IC driver rise/fall time ..2.000 ns
    IC driver switching voltage range ..3.00 V
    IC driver output impedance 1.0 ohms
, A- O! i& X" [  k. C% }    IC input capacitance ..... 7.0 pF
. }) S" p6 V( o  f9 O串扰门限为
# ^% |) [7 t( y& I  t- Y% m3 IMaximum allowed crosstalk ........... 200 mv peak
特定看一个网络：
- [' h' H- t4 K% t  NET = SOFT_TCK
   ELECTRICALLY ASSOCIATED NETS --------------------------------------
     None
6 h2 c( n5 P( {/ N2 ~1 I   AGGRESSOR NETS (Estimated peak crosstalk)
     NetFPGA1S_B22 .................. 233 mv
! Y" L* M( a/ C! B     Total estimated crosstalk ....................... 233 mv
     ** Warning ** Estimate exceeds maximum allowed crosstalk!
3 h8 K. V+ q( \: n2 ]) n7 l' |而我分配模型之后，该网络的串扰增加了很多：
* o/ ~( P' P4 |. E  NET = SOFT_TCK
9 n' V- M% D1 d   ELECTRICALLY ASSOCIATED NETS --------------------------------------
4 C; v2 q1 a4 h& T3 E     None
   AGGRESSOR NETS (Estimated peak crosstalk)
     NetFPGA1S_B22 ..................1268 mv
" L& a$ K" g) N  \) \' i( A     NetFPGA1S_A21 ..................1053 mv
' y% r9 d5 a8 j2 U8 d' \- [- o     NetFPGA1S_A20 .................. 456 mv
1 F6 a' L6 c4 B/ e5 ]- C( s     SOFT_TDI ....................... 319 mv
9 X, r: r! F* ^% ]% k     DIG5_SEG2 ...................... 227 mv
+ M$ U- e  r/ T+ W; h& q  `     Sum of the two strongest aggressors .............2321 mv
! O+ O6 Z6 ^. q. W4 w5 y     ** 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；