* SPICE netlist
R1 IN+ N004 100K
R2 N001 IN+ 5m
R3 N002 N003 10
C1 0 N003 10n Rser=1K
R4 IN+ N007 20K
R5 IN+ N005 36.5K
V1 IN+ 0 PULSE(0 12 0 20u 1u 200m 250m)
C2 0 N010 10n
C3 N009 0 1
C4 N005 0 10n
R6 N005 0 4.99K
R7 0 N010 4.99K
R8 N010 IN- 36.5K
C5 N013 0 0.1
R9 N013 IN- 1
R10 N015 IN- 5m
R11 OUT+ N008 20K
R12 OUT+ N006 36.5K
R13 N011 OUT- 36.5K
R14 N006 0 4.99K
R15 0 N011 4.99K
C6 OUT- N012 10n Rser=1K
C7 N012 N015 100n
C8 OUT+ 0 33 Rser=25m
C9 0 OUT- 33 Rser=25m
R16 OUT+ 0 10
R17 0 OUT- 10
R18 N012 N014 10
MQ1 N001 N002 OUT+ OUT+ SUM85N03-06P
MQ2 OUT- N014 N015 N015 SUM85N03-06P
XU1 N013 IN- N015 N012 N011 N010 N004 N009 0 N008 N007 N005 N006 N003 N001 IN+ LT4220 ;pnba VEE)SENSEK)SENSE-)GATE-)FB-)ON-)TRACK)TIMER)GND)PWRGD)_FAULT)ON+)FB+)GATE+)SENSE+)Vcc
I1 OUT+ 0 PWL(0 0 60m 0 120m 10 200m 10 260m 0) load
V2 0 IN- PULSE(0 12 0 20u 1u 200m 250m)
I2 0 OUT- PWL(0 0 60m 0 120m 10 200m 10 260m 0) load
.tran 400m startup

* LTspice schematic (.asc)
Version 4
SHEET 1 2144 976
WIRE -608 -472 -1056 -472
WIRE -352 -472 -608 -472
WIRE -176 -472 -352 -472
WIRE -32 -472 -176 -472
WIRE 0 -472 -32 -472
WIRE 112 -472 80 -472
WIRE 176 -472 112 -472
WIRE 528 -472 272 -472
WIRE 656 -472 528 -472
WIRE 784 -472 656 -472
WIRE 928 -472 784 -472
WIRE 1072 -472 928 -472
WIRE -1056 -456 -1056 -472
WIRE 928 -440 928 -472
WIRE 1072 -440 1072 -472
WIRE 784 -424 784 -472
WIRE 256 -408 256 -424
WIRE -352 -376 -352 -472
WIRE -176 -376 -176 -472
WIRE -1056 -360 -1056 -376
WIRE 784 -328 784 -360
WIRE 928 -328 928 -360
WIRE 1072 -328 1072 -360
WIRE 256 -296 256 -328
WIRE 320 -296 256 -296
WIRE 432 -296 384 -296
WIRE -608 -280 -608 -472
WIRE 528 -280 528 -472
WIRE 656 -248 656 -472
WIRE -176 -216 -176 -296
WIRE -32 -216 -32 -472
WIRE 112 -216 112 -472
WIRE 256 -216 256 -296
WIRE -608 -168 -608 -200
WIRE -480 -168 -608 -168
WIRE -400 -168 -480 -168
WIRE -608 -152 -608 -168
WIRE -480 -152 -480 -168
WIRE 656 -152 656 -168
WIRE 656 -152 592 -152
WIRE 656 -136 656 -152
WIRE -352 -120 -352 -296
WIRE -304 -120 -352 -120
WIRE 528 -120 528 -200
WIRE 528 -120 368 -120
WIRE -608 -56 -608 -72
WIRE -480 -56 -480 -88
WIRE -400 -40 -400 -168
WIRE -304 -40 -400 -40
WIRE 592 -40 592 -152
WIRE 592 -40 368 -40
WIRE 656 -40 656 -56
WIRE -384 40 -400 40
WIRE -304 40 -320 40
WIRE 384 40 368 40
WIRE -304 120 -400 120
WIRE 592 120 368 120
WIRE -608 136 -608 120
WIRE -480 152 -480 120
WIRE 656 152 656 136
WIRE -608 232 -608 216
WIRE -480 232 -480 216
WIRE -480 232 -608 232
WIRE -400 232 -400 120
WIRE -400 232 -480 232
WIRE -608 248 -608 232
WIRE 592 248 592 120
WIRE 656 248 656 232
WIRE 656 248 592 248
WIRE 256 264 256 216
WIRE 256 264 176 264
WIRE 320 264 256 264
WIRE 432 264 384 264
WIRE 656 264 656 248
WIRE -288 280 -320 280
WIRE -176 280 -176 216
WIRE -176 280 -224 280
WIRE 256 312 256 264
WIRE -176 344 -176 280
WIRE 176 344 176 264
WIRE 784 376 784 344
WIRE 960 376 960 344
WIRE 1072 376 1072 344
WIRE -1072 392 -1072 376
WIRE 256 440 256 392
WIRE -1072 488 -1072 472
WIRE -608 488 -608 328
WIRE -608 488 -1072 488
WIRE -176 488 -176 424
WIRE -176 488 -608 488
WIRE -32 488 -32 216
WIRE -32 488 -176 488
WIRE 0 488 -32 488
WIRE 112 488 112 216
WIRE 112 488 80 488
WIRE 176 488 176 408
WIRE 176 488 112 488
WIRE 240 488 176 488
WIRE 432 488 432 264
WIRE 432 488 336 488
WIRE 656 488 656 344
WIRE 656 488 432 488
WIRE 784 488 784 440
WIRE 784 488 656 488
WIRE 960 488 960 456
WIRE 960 488 784 488
WIRE 1072 488 1072 456
WIRE 1072 488 960 488
FLAG -1056 -360 0
FLAG 432 -296 0
FLAG -1072 376 0
FLAG -608 120 0
FLAG -320 280 0
FLAG 384 40 0
FLAG 1072 -472 OUT+
FLAG 1072 488 OUT-
FLAG -608 -472 IN+
FLAG -608 488 IN-
FLAG -480 -56 0
FLAG -608 -56 0
FLAG -400 40 0
FLAG -480 120 0
FLAG 1072 -328 0
FLAG 1072 344 0
FLAG 960 344 0
FLAG 928 -328 0
FLAG 784 -328 0
FLAG 784 344 0
FLAG 656 -40 0
FLAG 656 136 0
SYMBOL res -192 -392 R0
SYMATTR InstName R1
SYMATTR Value 100K
SYMBOL res 96 -488 R90
SYMATTR InstName R2
SYMATTR Value 5m
SYMBOL res 240 -424 R0
SYMATTR InstName R3
SYMATTR Value 10
SYMBOL cap 384 -312 R90
SYMATTR InstName C1
SYMATTR Value 10n
SYMATTR SpiceLine Rser=1K
SYMBOL res -368 -392 R0
SYMATTR InstName R4
SYMATTR Value 20K
SYMBOL res -624 -296 R0
SYMATTR InstName R5
SYMATTR Value 36.5K
SYMBOL voltage -1056 -472 R0
SYMATTR InstName V1
SYMATTR Value PULSE(0 12 0 20u 1u 200m 250m)
SYMBOL cap -496 152 R0
SYMATTR InstName C2
SYMATTR Value 10n
SYMBOL cap -320 24 R90
SYMATTR InstName C3
SYMATTR Value 1
SYMBOL cap -496 -152 R0
SYMATTR InstName C4
SYMATTR Value 10n
SYMBOL res -624 -168 R0
SYMATTR InstName R6
SYMATTR Value 4.99K
SYMBOL res -624 120 R0
SYMATTR InstName R7
SYMATTR Value 4.99K
SYMBOL res -624 232 R0
SYMATTR InstName R8
SYMATTR Value 36.5K
SYMBOL cap -224 264 R90
SYMATTR InstName C5
SYMATTR Value 0.1
SYMBOL res -192 328 R0
SYMATTR InstName R9
SYMATTR Value 1
SYMBOL res 96 472 R90
SYMATTR InstName R10
SYMATTR Value 5m
SYMBOL res 512 -296 R0
SYMATTR InstName R11
SYMATTR Value 20K
SYMBOL res 640 -264 R0
SYMATTR InstName R12
SYMATTR Value 36.5K
SYMBOL res 640 248 R0
SYMATTR InstName R13
SYMATTR Value 36.5K
SYMBOL res 640 -152 R0
SYMATTR InstName R14
SYMATTR Value 4.99K
SYMBOL res 640 136 R0
SYMATTR InstName R15
SYMATTR Value 4.99K
SYMBOL cap 384 248 R90
SYMATTR InstName C6
SYMATTR Value 10n
SYMATTR SpiceLine Rser=1K
SYMBOL cap 160 344 R0
SYMATTR InstName C7
SYMATTR Value 100n
SYMBOL cap 768 -424 R0
SYMATTR Value 33
SYMATTR SpiceLine Rser=25m
SYMATTR InstName C8
SYMBOL cap 768 376 R0
SYMATTR Value 33
SYMATTR SpiceLine Rser=25m
SYMATTR InstName C9
SYMBOL res 912 -456 R0
SYMATTR InstName R16
SYMATTR Value 10
SYMBOL res 944 360 R0
SYMATTR InstName R17
SYMATTR Value 10
SYMBOL res 240 296 R0
SYMATTR InstName R18
SYMATTR Value 10
SYMBOL nmos 176 -424 R270
SYMATTR InstName Q1
SYMATTR Value SUM85N03-06P
SYMBOL nmos 336 440 R90
SYMATTR InstName Q2
SYMATTR Value SUM85N03-06P
SYMBOL LT4220 32 -24 R0
SYMATTR InstName U1
SYMBOL current 1072 -440 R0
SYMATTR Value2 load
SYMATTR Value PWL(0 0 60m 0 120m 10 200m 10 260m 0)
SYMATTR InstName I1
SYMBOL voltage -1072 376 R0
SYMATTR InstName V2
SYMATTR Value PULSE(0 12 0 20u 1u 200m 250m)
SYMBOL current 1072 376 R0
SYMATTR Value2 load
SYMATTR Value PWL(0 0 60m 0 120m 10 200m 10 260m 0)
SYMATTR InstName I2