* SPICE netlist
R1 IN N005 64.9K
R2 N005 N006 4.02K
C1 N010 0 33n
C2 0 N004 20n
R3 N002 N003 10
R4 N004 N003 100
R5 IN N001 20m
M1 N001 N002 OUT OUT SUD40N10-25
R6 OUT N007 36.5K
R7 N007 0 4.02K
C3 OUT 0 225 Rser=10m
V1 IN 0 PWL(0 0 20u 48 0.1 48 0.2 90 0.3 48)
R9 OUT 0 24
C4 N005 0 .1
XU1 N005 N006 MP_01 N008 N009 MP_02 0 0 N010 N007 MP_03 OUT N003 MP_04 N001 IN LT4256-3 ;pnba UV)OV))Open)PWRGD))Retry)GND)Timer)FB))Vout)Gate))Sense)Vcc
D1 OUT N002 BZX84C12L
R8 OUT N009 51K
R10 N006 0 4.02K
R11 N008 N011 10K
C5 N008 0 .01
V2 N011 0 3.3
.tran 0.4 startup

* LTspice schematic (.asc)
Version 4
SHEET 1 1728 672
WIRE -336 -336 -864 -336
WIRE 80 -336 -336 -336
WIRE 112 -336 80 -336
WIRE 208 -336 192 -336
WIRE 320 -336 208 -336
WIRE 704 -336 416 -336
WIRE 768 -336 704 -336
WIRE 864 -336 768 -336
WIRE -864 -320 -864 -336
WIRE 864 -320 864 -336
WIRE 768 -304 768 -336
WIRE -336 -272 -336 -336
WIRE 400 -256 400 -288
WIRE 560 -256 400 -256
WIRE 704 -256 704 -336
WIRE 704 -256 624 -256
WIRE 400 -240 400 -256
WIRE -864 -224 -864 -240
WIRE 768 -224 768 -240
WIRE 864 -224 864 -240
WIRE 80 -192 80 -336
WIRE 208 -192 208 -336
WIRE 400 -128 400 -160
WIRE 400 -128 304 -128
WIRE 448 -128 400 -128
WIRE 544 -128 528 -128
WIRE -336 -96 -336 -192
WIRE -336 -96 -448 -96
WIRE 0 -96 -336 -96
WIRE -448 -80 -448 -96
WIRE -336 -80 -336 -96
WIRE 704 -48 704 -256
WIRE 704 -48 304 -48
WIRE 0 -16 -240 -16
WIRE -448 16 -448 -16
WIRE -336 16 -336 0
WIRE -240 16 -240 -16
WIRE -240 16 -336 16
WIRE 528 32 304 32
WIRE 592 32 528 32
WIRE 704 32 704 -48
WIRE 704 32 672 32
WIRE -336 48 -336 16
WIRE 0 64 -176 64
WIRE 528 64 528 32
WIRE 704 64 704 32
WIRE 464 112 304 112
WIRE -336 160 -336 128
WIRE -80 160 -96 160
WIRE 0 160 -16 160
WIRE 528 160 528 144
WIRE -304 192 -368 192
WIRE -176 192 -176 64
WIRE -176 192 -224 192
WIRE 320 192 304 192
WIRE 464 208 464 112
WIRE 704 208 704 144
WIRE 704 208 464 208
WIRE -368 224 -368 192
WIRE -176 256 -176 192
WIRE 144 256 144 240
WIRE -368 336 -368 304
WIRE -176 336 -176 320
FLAG 608 -128 0
FLAG -96 160 0
FLAG 528 160 0
FLAG -864 -224 0
FLAG 864 -224 0
FLAG -448 16 0
FLAG 768 -224 0
FLAG 144 256 0
FLAG -336 160 0
FLAG -176 336 0
FLAG -368 336 0
FLAG -864 -336 IN
FLAG 864 -336 OUT
FLAG 320 192 0
SYMBOL res -352 -288 R0
SYMATTR InstName R1
SYMATTR Value 64.9K
SYMBOL res -352 -96 R0
SYMATTR InstName R2
SYMATTR Value 4.02K
SYMBOL cap -16 144 R90
SYMATTR InstName C1
SYMATTR Value 33n
SYMBOL cap 608 -144 R90
SYMATTR InstName C2
SYMATTR Value 20n
SYMBOL res 384 -256 R0
SYMATTR InstName R3
SYMATTR Value 10
SYMBOL res 544 -144 R90
SYMATTR InstName R4
SYMATTR Value 100
SYMBOL res 96 -320 R270
SYMATTR InstName R5
SYMATTR Value 20m
SYMBOL nmos 320 -288 R270
SYMATTR InstName M1
SYMATTR Value SUD40N10-25
SYMBOL res 688 16 R90
SYMATTR InstName R6
SYMATTR Value 36.5K
SYMBOL res 512 48 R0
SYMATTR InstName R7
SYMATTR Value 4.02K
SYMBOL cap 752 -304 R0
SYMATTR InstName C3
SYMATTR Value 225
SYMATTR SpiceLine Rser=10m
SYMBOL voltage -864 -336 R0
SYMATTR Value PWL(0 0 20u 48 0.1 48 0.2 90 0.3 48)
SYMATTR InstName V1
SYMBOL res 848 -336 R0
SYMATTR InstName R9
SYMATTR Value 24
SYMBOL cap -464 -80 R0
SYMATTR InstName C4
SYMATTR Value .1
SYMBOL LT4256-3 144 0 R0
SYMATTR InstName U1
SYMBOL zener 624 -272 R90
SYMATTR InstName D1
SYMATTR Value BZX84C12L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res 688 48 R0
SYMATTR InstName R8
SYMATTR Value 51K
SYMBOL res -352 32 R0
SYMATTR InstName R10
SYMATTR Value 4.02K
SYMBOL res -208 208 M270
SYMATTR InstName R11
SYMATTR Value 10K
SYMBOL cap -192 256 R0
SYMATTR InstName C5
SYMATTR Value .01
SYMBOL voltage -368 208 R0
SYMATTR InstName V2
SYMATTR Value 3.3