Current-Control Oscillator problem

Current-Control Oscillator problem

I am designing a Current-Control Oscillator .
But it can not work in hspice,
when I set the initial value of n1, n2 in hspice:
.IC V(n1)= vcc V(n2)= 0

then it can work.
Without the initial value, it can not work.
I also find the reason why it can not work with hspice:
without the initial value, the n1 = n2 = 1 (high)
then the output of A24 or A25 will be low ( another will
be high).
So, if A24 output 0 (low) , C1 been charged by M4,
A25 must be output 1, C2 been discharged by M7.

But in hspice, if A24 output 0 (low) , C1 can not charge over Vref,
so the n1 always keep high, and the Oscillator can not work.
Though I find the reason, but I do not know why it happy,
Is the simulation software( hspice) problem or the
circuit problem ?
May I need a start-up circuit ?

BTW: When it work with the initial value,
C1, C2 charged current is: 176uA
discharged current is: 13.1uA
Frequency = 6.17M
Vdd= 3.3V Vref = 1.25V

**broken link removed**

1.in my opinion, if u want the oscaillator to start oscallte, the phase dealy after the loop back should be 180°, and gain >=1. usually in ring oscillator, odd stage (180°) is used. if even stage (360°) is used, u should take more care in the phase delay after loop back.
2.in ur case, 8 stage is used.
and there exist a stable state when n1=n2=0,
cause in this case, the output of A13 & A14 is 1 ===> output of A24 & A25 are 0
===> C1top & C2top are high > Vref ===> n1=n2=0.
3. maybe insert a inverter to form 9 stage
4. in simulation, we usually skip initial condition, by using ramping VCC, try this.
5. At most of time, simulator is usually right if u provide it a correct model, and input stimulus.

modified the A13 and A14 for a more better structre.
such as added pull up Res for initial state

If OSC is simulated only,I think you can add the initial state. Once you connect osc with other. perhaps the initial state is not needed and osc can work.

Thanks for all !
I will try and paste the result.