* SPICE netlist
V1 0 VEE PWL(0 0 10u 48)
M1 OUT N017 N018 N018 PSMN4R8100BSE M=2
RS1 N018 VEE .5m
RD N015 OUT 100K
RDT N012 OUT 200K
RDB N012 VEE 5.11K
R6 N001 N008 100K
R7 N001 PGIO1 100K
RRT N002 0 200K
RRB VEE N002 5.11K
RIN 0 N001 4K
RUV3 0 N005 487K
RUV1 N005 N007 14.3K
CTMR N010 VEE 4.7n
CL 0 OUT 500
ROT N004 N006 1.4K
ROB N006 VEE 10K
S1 0 OUT N013 0 SSHORT
V2 N013 0 PWL(0 0 1.2 0 +10n 0 +20m 0 +10n 0)
CVCC VEE N003 1
CIN N001 VEE .1
XU1 VEE N005 N005 N007 N004 N006 MP_01 MP_02 MP_03 MP_04 VEE MP_05 MP_06 VEE N018 MP_07 MP_08 N014 MP_09 N015 N012 N002 N011 N010 MP_10 MP_11 MP_12 MP_13 PGIO1 N008 VEE N003 MP_14 MP_15 MP_16 MP_17 MP_18 MP_19 MP_20 MP_21 MP_22 N003 N001 N001 LTC4283 A6=0 A5=0 A4=1 A3=1 A2=0 B7=0 B6=0 B5=0 B4=0 B3=0 B2=0 B1=1 B0=1 D7=0 D6=0 D5=0 D4=1 D3=1 D2=1 D1=0 D0=0 E7=1 E6=1 E5=0 E4=0 E3=0 E2=0 E1=0 F7=0 ;pnba _EN)UVL)UVH)OV)Vref)Voutth)))))Vee)))Sense-)Sense+)))Gate))Drain)Drns)Rtns)Ramp)Tmr)))))PGIO1)PGIO2)PGIO3)PGIO4))))))))))IntVcc)Vin)Vz
RG2 N014 N016 470
CG2 N016 VEE 100n
RUV2 N007 VEE 10K
R1 N010 N009 18.2K
CTMR1 N009 VEE 68n
R2 N009 VEE 1.13Meg
RG1 N014 N017 10
B1 0 OUT I=if(V(PGIO1,VEE)<.5 & time > .1,MIN(Power/MAX(V(0,OUT),12),Imax),0)
.tran 1.6
.param Power=600
.param Imax=120

* LTspice schematic (.asc)
Version 4
SHEET 1 2816 1024
WIRE -144 -496 -144 -512
WIRE -384 -400 -1200 -400
WIRE -272 -400 -384 -400
WIRE -144 -400 -144 -416
WIRE -144 -400 -208 -400
WIRE -384 -368 -384 -400
WIRE 432 -368 400 -368
WIRE 544 -368 512 -368
WIRE 576 -368 544 -368
WIRE 1152 -368 656 -368
WIRE -1136 -304 -1136 -320
WIRE -144 -304 -144 -400
WIRE -48 -304 -144 -304
WIRE 976 -304 -48 -304
WIRE -384 -288 -384 -304
WIRE 704 -288 -384 -288
WIRE -384 -272 -384 -288
WIRE -144 -272 -144 -304
WIRE -48 -272 -48 -304
WIRE 544 -272 544 -368
WIRE 1040 -240 688 -240
WIRE 1040 -224 1040 -240
WIRE -1136 -208 -1136 -224
WIRE -496 -208 -1136 -208
WIRE 1008 -176 688 -176
WIRE -1136 -144 -1136 -208
WIRE -496 -144 -1136 -144
WIRE -1136 -128 -1136 -144
WIRE 1008 -128 1008 -176
WIRE 1040 -128 1040 -144
WIRE 1040 -128 1008 -128
WIRE 752 -112 688 -112
WIRE 864 -112 752 -112
WIRE 976 -112 976 -304
WIRE 976 -112 944 -112
WIRE 1040 -112 1040 -128
WIRE -496 -80 -992 -80
WIRE 800 -48 688 -48
WIRE 976 -48 976 -112
WIRE 976 -48 880 -48
WIRE -1136 -32 -1136 -48
WIRE -992 -32 -992 -80
WIRE -992 -32 -1136 -32
WIRE -816 -16 -960 -16
WIRE -768 -16 -816 -16
WIRE -656 -16 -688 -16
WIRE -496 -16 -656 -16
WIRE -1136 0 -1136 -32
WIRE -960 16 -960 -16
WIRE 1040 16 1040 -32
WIRE 1040 16 688 16
WIRE 1152 16 1152 -368
WIRE 1152 16 1040 16
WIRE -496 48 -528 48
WIRE -816 64 -816 -16
WIRE -656 64 -656 -16
WIRE 704 80 704 -288
WIRE 704 80 688 80
WIRE -496 112 -576 112
WIRE 1280 112 1280 80
WIRE 1344 128 1328 128
WIRE 800 144 688 144
WIRE 912 144 800 144
WIRE 1360 176 1328 176
WIRE 272 192 272 176
WIRE 272 192 112 192
WIRE 544 192 544 176
WIRE 1360 192 1360 176
WIRE -1200 208 -1200 -400
WIRE -1136 208 -1136 80
WIRE -1136 208 -1200 208
WIRE -960 208 -960 96
WIRE -960 208 -1136 208
WIRE -816 208 -816 128
WIRE -816 208 -960 208
WIRE -656 208 -656 128
WIRE -656 208 -816 208
WIRE -576 208 -576 112
WIRE -576 208 -656 208
WIRE -384 208 -384 176
WIRE -384 208 -576 208
WIRE 112 208 112 192
WIRE 800 224 800 144
WIRE 912 224 912 144
WIRE 272 240 272 192
WIRE -1408 288 -1408 256
WIRE 112 304 112 288
WIRE 1360 304 1360 272
WIRE 272 352 272 320
WIRE -1408 400 -1408 368
WIRE -384 400 -384 208
WIRE -384 400 -1408 400
WIRE -192 400 -192 176
WIRE -192 400 -384 400
WIRE -176 400 -192 400
WIRE -80 400 -80 176
WIRE -80 400 -96 400
WIRE 256 400 -80 400
WIRE 544 400 544 272
WIRE 544 400 352 400
WIRE 1168 400 1168 368
WIRE 1408 400 1408 368
WIRE -384 480 -384 400
WIRE 112 480 112 368
WIRE 112 480 -384 480
WIRE 912 480 912 304
WIRE 912 480 112 480
WIRE 1040 480 1040 16
WIRE 1040 480 912 480
WIRE 544 512 544 400
WIRE 800 512 800 304
WIRE 800 512 544 512
WIRE 1168 512 1168 464
WIRE 1168 512 800 512
WIRE 1280 512 1280 192
WIRE 1280 512 1168 512
WIRE 1408 512 1408 480
WIRE 1408 512 1280 512
FLAG -1408 256 0
FLAG 400 -368 0
FLAG -144 -512 0
FLAG -1136 -320 0
FLAG 1168 368 0
FLAG 1280 80 0
FLAG 1360 304 0
FLAG 1344 128 0
FLAG -1408 400 VEE
FLAG 1408 512 OUT
FLAG 752 -112 PGIO1
FLAG 1408 368 0
SYMBOL voltage -1408 272 R0
SYMATTR InstName V1
SYMATTR Value PWL(0 0 10u 48)
SYMBOL nmos 352 352 R90
SYMATTR InstName M1
SYMATTR Value PSMN4R8100BSE
SYMATTR Value2 M=2
SYMBOL res -80 384 R90
SYMATTR InstName RS1
SYMATTR Value .5m
SYMBOL res 528 176 R0
SYMATTR InstName RD
SYMATTR Value 100K
SYMBOL res 784 208 R0
SYMATTR InstName RDT
SYMATTR Value 200K
SYMBOL res 896 208 R0
SYMATTR InstName RDB
SYMATTR Value 5.11K
SYMBOL res 896 -64 R90
SYMATTR InstName R6
SYMATTR Value 100K
SYMBOL res 960 -128 R90
SYMATTR InstName R7
SYMATTR Value 100K
SYMBOL res 528 -384 R90
SYMATTR InstName RRT
SYMATTR Value 200K
SYMBOL res 672 -384 R90
SYMATTR InstName RRB
SYMATTR Value 5.11K
SYMBOL res -160 -512 R0
SYMATTR InstName RIN
SYMATTR Value 4K
SYMBOL res -1152 -320 R0
SYMATTR InstName RUV3
SYMATTR Value 487K
SYMBOL res -1152 -144 R0
SYMATTR InstName RUV1
SYMATTR Value 14.3K
SYMBOL cap -672 64 R0
SYMATTR InstName CTMR
SYMATTR Value 4.7n
SYMBOL cap 1152 400 R0
SYMATTR InstName CL
SYMATTR Value 500
SYMBOL res 1024 -240 R0
SYMATTR InstName ROT
SYMATTR Value 1.4K
SYMBOL res 1024 -128 R0
SYMATTR InstName ROB
SYMATTR Value 10K
SYMBOL sw 1280 96 M0
SYMATTR InstName S1
SYMATTR Value SSHORT
SYMBOL voltage 1360 176 R0
SYMATTR InstName V2
SYMATTR Value PWL(0 0 1.2 0 +10n 0 +20m 0 +10n 0)
SYMBOL cap -400 -368 R0
SYMATTR InstName CVCC
SYMATTR Value 1
SYMBOL cap -208 -416 R90
SYMATTR InstName CIN
SYMATTR Value .1
SYMBOL LTC4283 96 -48 R0
SYMATTR InstName U1
SYMATTR SpiceLine D7=0 D6=0 D5=0 D4=1 D3=1 D2=1 D1=0 D0=0
SYMATTR Value2 A6=0 A5=0 A4=1 A3=1 A2=0 B7=0 B6=0 B5=0 B4=0 B3=0 B2=0 B1=1 B0=1
SYMBOL res 96 192 R0
SYMATTR InstName RG2
SYMATTR Value 470
SYMBOL cap 96 304 R0
SYMATTR InstName CG2
SYMATTR Value 100n
SYMBOL res -1152 -16 R0
SYMATTR InstName RUV2
SYMATTR Value 10K
SYMBOL res -672 -32 R90
SYMATTR InstName R1
SYMATTR Value 18.2K
SYMBOL cap -832 64 R0
SYMATTR InstName CTMR1
SYMATTR Value 68n
SYMBOL res -976 0 R0
SYMATTR InstName R2
SYMATTR Value 1.13Meg
SYMBOL res 256 224 R0
SYMATTR InstName RG1
SYMATTR Value 10
SYMBOL bi 1408 400 R0
SYMATTR InstName B1
SYMATTR Value I=if(V(PGIO1,VEE)<.5 & time > .1,MIN(Power/MAX(V(0,OUT),12),Imax),0)