大佬能帮我看看为什么我的环形振荡器

jfk1997

为什么总是不收敛吗？这是我的代码

V1 (supply 0) vsource type=dc dc=VSUPPLY
V2 (gnd 0) vsource type=dc dc=0
V3 (ctrl 0) vsource type=pwl wave=[0 0 5p 0 10p VSUPPLY ]

//15-stage nand ring oscillator
X1    (out1  in1 ctrl supply gnd) nand
X2    (out2  out1  out1  supply gnd) nand
X3    (out3  out2  out2  supply gnd) nand
X4    (out4  out3  out3  supply gnd) nand
X5    (out5  out4  out4  supply gnd) nand
X6    (out6  out5  out5  supply gnd) nand
X7    (out7  out6  out6  supply gnd) nand
X8    (out8  out7  out7  supply gnd) nand
X9    (out9  out8  out8  supply gnd) nand
X10   (out10 out9  out9  supply gnd) nand
X11   (out11 out10 out10 supply gnd) nand
X12   (out12 out11 out11 supply gnd) nand
X13   (out13 out12 out12 supply gnd) nand
X14   (out14 out13 out13 supply gnd) nand
X15   (in1   out14 out14 supply gnd) nand

//sub-circuit nand, series resistance included
subckt nand out in1 in2 supply gnd
R1  (out out1         ) resistor r=RSeries/WMin
I1  (out1 in1 supply1 ) RFET type=p W=1*WMin
R2  (supply1 supply   ) resistor r=RSeries/WMin

R3  (out out2         ) resistor r=RSeries/WMin
I2  (out2 in2 supply2 ) RFET type=p W=1*WMin
R4  (supply2 supply   ) resistor r=RSeries/WMin

R5  (out out3         ) resistor r=RSeries/WMin
I3  (out3 in1 t11     ) RFET type=n W=1*WMin
R6  (t11 t1           ) resistor r=RSeries/WMin

R7  (t1 t12           ) resistor r=RSeries/WMin
I4  (t12  in2 gnd1    ) RFET type=n W=1*WMin
R8  (gnd1 gnd         ) resistor r=RSeries/WMin

CLoad11 (in1  0) capacitor c=CParasitic*WMin
ends

//initial condition
ic out1=VSUPPLY out2=0 out3=VSUPPLY out4=0 out5=VSUPPLY out6=0 out7=VSUPPLY out8=0 out9=VSUPPLY out10=0 out11=VSUPPLY out12=0 out13=VSUPPLY out14=0 in1=VSUPPLY

simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-8 temp=27 \
    tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 cmin=1e-18 \
    digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \
    checklimitdest=psf

//transient analysis
tran tran stop=10n write="spectre.ic" writefinal="spectre.fc" annotate=status maxiters=5 autostop=yes

jfk1997

up，新手求教