* SPICE netlist
R1 N003 IN2 4m
MQ1 N003 N006 OUT2 OUT2 IRF7413
R2 OUT2 N004 14.3K
R3 N004 0 5.11K
R4 OUT2 N007 10K
C1 N011 0 100n
C3 OUT2 0 100
Rload OUT2 0 .5
C2 N012 0 1n
MQ2 N001 N005 OUT1 OUT1 IRF7413
R5 N001 IN1 4m
V3 IN1 0 PWL(0 0 100u 3.3)
R6 OUT2 N010 20K
R7 N010 0 5.11K
R8 OUT2 N009 10K
C4 OUT1 0 100
Rload1 OUT1 0 .66
S2 0 OUT1 N002 0 Sload
V4 N002 0 PULSE(0 1 200m 10n 10n 10m 5)
V5 ON1 0 PWL(0 0 10m 0 +100n 3.3 + 300m 3.3 +100n .2 +20u .2 +100n 3.3)
XU1 ON1 IN1 N001 N005 N010 N009 N008 N012 N011 0 N007 N004 N006 N003 IN2 ON2 LTC4221 ;pnba On1)Vcc1)Sense1)Gate1)Fb1)Pwrgd1)_Fault)Filter)Timer)Gnd)Pwrgd2)Fb2)Gate2)Sense2)Vcc2)On2
V1 IN2 0 PWL(0 0 100u 2.5)
V6 ON2 0 PWL(0 0 10m 0 +100n 3.3)
.tran 500m

* LTspice schematic (.asc)
Version 4
SHEET 1 2576 864
WIRE -280 -416 -1288 -416
WIRE -264 -416 -280 -416
WIRE -168 -416 -184 -416
WIRE -136 -416 -168 -416
WIRE 904 -416 -40 -416
WIRE 1000 -416 904 -416
WIRE 1144 -416 1000 -416
WIRE -1288 -400 -1288 -416
WIRE 904 -400 904 -416
WIRE 1000 -400 1000 -416
WIRE 1144 -400 1144 -416
WIRE 1288 -384 1192 -384
WIRE 1288 -368 1288 -384
WIRE 1208 -336 1192 -336
WIRE -1288 -304 -1288 -320
WIRE 904 -304 904 -336
WIRE 1000 -304 1000 -320
WIRE 1144 -304 1144 -320
WIRE 1288 -256 1288 -288
WIRE 72 -208 -1288 -208
WIRE 88 -208 72 -208
WIRE 184 -208 168 -208
WIRE 216 -208 184 -208
WIRE 504 -208 312 -208
WIRE 632 -208 504 -208
WIRE 712 -208 632 -208
WIRE 792 -208 712 -208
WIRE 904 -208 792 -208
WIRE 1000 -208 904 -208
WIRE -1288 -192 -1288 -208
WIRE 904 -192 904 -208
WIRE 1000 -192 1000 -208
WIRE 504 -176 504 -208
WIRE 632 -112 632 -208
WIRE 792 -112 792 -208
WIRE -1288 -96 -1288 -112
WIRE 904 -96 904 -128
WIRE 1000 -96 1000 -112
WIRE 504 -80 504 -96
WIRE 504 -80 456 -80
WIRE -280 -64 -280 -416
WIRE -168 -64 -168 -416
WIRE -56 -64 -56 -368
WIRE 72 -64 72 -208
WIRE 184 -64 184 -208
WIRE 296 -64 296 -160
WIRE 504 -48 504 -80
WIRE -392 16 -1288 16
WIRE 456 16 456 -80
WIRE 456 16 408 16
WIRE -1288 32 -1288 16
WIRE 504 48 504 32
WIRE 712 48 712 -208
WIRE -392 96 -872 96
WIRE 632 96 632 -32
WIRE 632 96 408 96
WIRE -872 112 -872 96
WIRE -1288 128 -1288 112
WIRE -392 176 -424 176
WIRE 792 176 792 -32
WIRE 792 176 408 176
WIRE -872 208 -872 192
WIRE -392 256 -424 256
WIRE 712 256 712 128
WIRE 712 256 408 256
WIRE 712 272 712 256
WIRE -168 352 -168 336
WIRE 184 352 184 336
WIRE 712 368 712 352
WIRE -168 432 -168 416
WIRE 184 432 184 416
FLAG 504 48 0
FLAG -168 432 0
FLAG -1288 -96 0
FLAG 904 -96 0
FLAG 1000 -96 0
FLAG 184 432 0
FLAG -424 256 0
FLAG -1288 -304 0
FLAG 712 368 0
FLAG 904 -304 0
FLAG 1000 -304 0
FLAG 1144 -304 0
FLAG 1208 -336 0
FLAG 1288 -256 0
FLAG -1288 128 0
FLAG -872 208 0
FLAG 1000 -416 OUT1
FLAG 1000 -208 OUT2
FLAG -1288 -416 IN1
FLAG -1288 -208 IN2
FLAG -1288 16 ON1
FLAG -872 96 ON2
SYMBOL res 184 -224 R90
SYMATTR InstName R1
SYMATTR Value 4m
SYMBOL nmos 216 -160 R270
SYMATTR InstName Q1
SYMATTR Value IRF7413
SYMBOL res 488 -192 R0
SYMATTR InstName R2
SYMATTR Value 14.3K
SYMBOL res 488 -64 R0
SYMATTR InstName R3
SYMATTR Value 5.11K
SYMBOL res 616 -128 R0
SYMATTR InstName R4
SYMATTR Value 10K
SYMBOL cap -184 352 R0
SYMATTR Value 100n
SYMATTR InstName C1
SYMBOL cap 888 -192 R0
SYMATTR InstName C3
SYMATTR Value 100
SYMBOL res 984 -208 R0
SYMATTR InstName Rload
SYMATTR Value .5
SYMBOL cap 168 352 R0
SYMATTR Value 1n
SYMATTR InstName C2
SYMBOL nmos -136 -368 R270
SYMATTR InstName Q2
SYMATTR Value IRF7413
SYMBOL res -168 -432 R90
SYMATTR InstName R5
SYMATTR Value 4m
SYMBOL voltage -1288 -416 R0
SYMATTR InstName V3
SYMATTR Value PWL(0 0 100u 3.3)
SYMBOL res 696 32 R0
SYMATTR InstName R6
SYMATTR Value 20K
SYMBOL res 696 256 R0
SYMATTR InstName R7
SYMATTR Value 5.11K
SYMBOL res 776 -128 R0
SYMATTR InstName R8
SYMATTR Value 10K
SYMBOL cap 888 -400 R0
SYMATTR InstName C4
SYMATTR Value 100
SYMBOL res 984 -416 R0
SYMATTR InstName Rload1
SYMATTR Value .66
SYMBOL sw 1144 -304 R180
SYMATTR InstName S2
SYMATTR Value Sload
SYMBOL voltage 1288 -384 R0
SYMATTR InstName V4
SYMATTR Value PULSE(0 1 200m 10n 10n 10m 5)
SYMBOL voltage -1288 16 R0
SYMATTR Value2 + 300m 3.3 +100n .2
SYMATTR SpiceLine +20u .2 +100n 3.3)
SYMATTR InstName V5
SYMATTR Value PWL(0 0 10m 0 +100n 3.3
SYMBOL LTC4221 8 112 R0
SYMATTR InstName U1
SYMBOL voltage -1288 -208 R0
SYMATTR InstName V1
SYMATTR Value PWL(0 0 100u 2.5)
SYMBOL voltage -872 96 R0
SYMATTR InstName V6
SYMATTR Value PWL(0 0 10m 0 +100n 3.3)