35mhz above pierce crystal oscillator help!!

[xerxer]

i am a new comer for cystal osicllator .a 35mhz pierce oscillator need to be designed

and ac simulation result is shown the freqency on oscillation point is 3db.


i think the ac simulation recovered that the circuit can oscillate ,but the tran leads to stablity .i don't know what's wrong with the circuit :schematic or simulation method of tran .
the sp file is shown below:

.lib 'e:\lyk\spice_lib\mylib.lib' tt

vcc vcc 0 pwl 0 0 1n 5
.tran 15n 500u

* Main network description
RI8 N_11 N_7 10000K
RI15 N_6 N_5 18
RI25 out N_10 2K
LI7 N_5 acout 9MH
CI3 out gnd 40PF
CI4 acout gnd 20PF
CI19 N_10 N_7 22PF
CI5 out N_6 0.0020718PF
CI21 out acout 4PF
MI2 N_7 N_11 gnd gnd MN L=1U W=10U M=15
MI1 N_7 N_11 vcc vcc MP L=1U W=10U M=40

.end

 

[hung_wai_ming@hotmail.com]

Are u using Hspice?
There are at least some tricks for XOSC start-up
(1) accurate option
(2) Init current in C in model
(3) Init voltage in L in model
(4) Smaller time step <10ns

Why u have different loading cap in two XOSC legs?