* SPICE netlist
R1 TC 0 56.2K
V1 IN 0 48
C1 VC P001 4700p
C2 0 INTVCC 4.7
R2 Bct Rfb 243K
R3 0 N003 6.04K
L1 IN Act 60.8 Rpar=5K
L2 0 N001 3.8 Rpar=5K
C3 OUT 0 100
D1 N001 OUT 30BQ060
R4 P001 0 10K
C4 0 SS 1p
R5 IN N002 412K
R6 N002 0 15.4K
XU1 0 MP_01 MP_02 gate IN INTVCC N002 MP_03 MP_04 SS N004 VC Rfb N003 TC LT3748 ;pnba GND)))Gate)Vin)INTVcc)EN/UVLO)))SS)Sense)Vc)Rfb)Rref)TC
R7 N004 0 33m
M1 Act gate N004 N004 Si4490DY
E1 Act Bct A B 1
@1 A B delay=2.5m fstart=200 fend=6.4k oct=2 fcoarse=800 nmax=1 3 1k 3 1.01k 1 pp0=1 pp1=250m f0=400 f1=1.6K tavgmin=1m tsettle=500u
A1 N005 0 N007 0 0 0 N006 0 SAMPLEHOLD Vhigh=100 ref=8m
B1 N005 0 V=absdelay(V(Act,IN),100n)
B2 N007 0 V=V(IN,Rfb)
E2 A 0 N006 0 1
ILOAD OUT 0 PULSE(0 2 10u 500u 500u 1)
K1 L1 L2 1.
.fra
.options trtol=4
.ic V(OUT)=12.2 V(INTVCC)=7

* LTspice schematic (.asc)
Version 4
SHEET 1 1120 928
WIRE -400 -464 -512 -464
WIRE -208 -464 -400 -464
WIRE 224 -464 -208 -464
WIRE 352 -464 272 -464
WIRE 448 -464 416 -464
WIRE 560 -464 448 -464
WIRE 224 -448 224 -464
WIRE 272 -448 272 -464
WIRE 560 -448 560 -464
WIRE -512 -432 -512 -464
WIRE -400 -432 -400 -464
WIRE 448 -432 448 -464
WIRE -512 -336 -512 -352
WIRE 272 -336 272 -368
WIRE 448 -336 448 -368
WIRE 560 -336 560 -368
WIRE 112 -320 96 -320
WIRE 192 -320 176 -320
WIRE -208 -288 -208 -464
WIRE 96 -288 96 -320
WIRE 144 -288 96 -288
WIRE 144 -272 144 -288
WIRE 192 -272 192 -320
WIRE 224 -272 224 -368
WIRE -544 -224 -560 -224
WIRE -400 -224 -400 -352
WIRE -400 -224 -464 -224
WIRE -368 -224 -400 -224
WIRE -16 -224 -48 -224
WIRE 16 -224 -16 -224
WIRE 112 -224 96 -224
WIRE 128 -224 112 -224
WIRE 224 -224 224 -272
WIRE 224 -224 208 -224
WIRE -496 -144 -560 -144
WIRE -384 -144 -416 -144
WIRE -368 -144 -384 -144
WIRE 16 -144 -48 -144
WIRE 128 -144 96 -144
WIRE 224 -144 224 -224
WIRE -544 -64 -560 -64
WIRE -384 -64 -400 -64
WIRE -368 -64 -384 -64
WIRE 80 -64 -48 -64
WIRE 176 -64 80 -64
WIRE -496 16 -560 16
WIRE -416 16 -432 16
WIRE -368 16 -416 16
WIRE 224 16 224 -48
WIRE 224 16 -48 16
WIRE 224 32 224 16
WIRE -272 96 -272 80
WIRE -144 128 -144 80
WIRE 224 128 224 112
WIRE -144 160 -144 128
WIRE -432 288 -512 288
WIRE -224 288 -352 288
WIRE -224 320 -224 288
WIRE -192 320 -224 320
WIRE 96 352 96 320
WIRE 48 368 -16 368
WIRE -192 384 -224 384
WIRE -432 400 -512 400
WIRE -224 400 -224 384
WIRE -224 400 -352 400
WIRE 48 416 16 416
WIRE -192 464 -192 448
WIRE 96 464 96 432
FLAG -560 16 0
FLAG -560 -64 0
FLAG -560 -144 0
FLAG -512 -336 0
FLAG -144 224 0
FLAG 128 -144 0
FLAG 448 -336 0
FLAG 272 -336 0
FLAG 560 -336 0
FLAG -512 -464 IN
FLAG 560 -464 OUT
FLAG -560 -224 0
FLAG -272 96 0
FLAG 224 128 0
FLAG -416 16 SS
FLAG 224 -272 Act
FLAG 112 -224 Bct
FLAG 80 -64 gate
FLAG -16 -224 Rfb
FLAG 96 320 A
FLAG -192 464 0
FLAG -512 288 0
FLAG -512 400 0
FLAG 16 416 0
FLAG 96 464 0
FLAG 192 -320 A
FLAG -384 -64 VC
FLAG -384 -144 TC
FLAG -144 128 INTVCC
FLAG 96 -320 B
SYMBOL res -400 -160 R90
SYMATTR InstName R1
SYMATTR Value 56.2K
SYMBOL voltage -512 -448 R0
SYMATTR InstName V1
SYMATTR Value 48
SYMBOL cap -400 -80 R90
SYMATTR InstName C1
SYMATTR Value 4700p
SYMBOL cap -160 224 M180
SYMATTR InstName C2
SYMATTR Value 4.7
SYMBOL res 112 -240 R90
SYMATTR InstName R2
SYMATTR Value 243K
SYMBOL res 112 -160 R90
SYMATTR InstName R3
SYMATTR Value 6.04K
SYMBOL ind2 208 -464 R0
SYMATTR InstName L1
SYMATTR Value 60.8
SYMATTR Type ind
SYMATTR SpiceLine Rpar=5K
SYMBOL ind2 288 -352 R180
SYMATTR InstName L2
SYMATTR Value 3.8
SYMATTR Type ind
SYMATTR SpiceLine Rpar=5K
SYMBOL cap 432 -432 R0
SYMATTR InstName C3
SYMATTR Value 100
SYMBOL schottky 352 -448 R270
SYMATTR InstName D1
SYMATTR Value 30BQ060
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res -448 -80 R90
SYMATTR InstName R4
SYMATTR Value 10K
SYMBOL cap -496 0 M90
SYMATTR InstName C4
SYMATTR Value 1p
SYMBOL res -416 -448 R0
SYMATTR InstName R5
SYMATTR Value 412K
SYMBOL res -448 -240 R90
SYMATTR InstName R6
SYMATTR Value 15.4K
SYMBOL PowerProducts\\LT3748 -208 -112 R0
SYMATTR InstName U1
SYMBOL res 208 16 R0
SYMATTR InstName R7
SYMATTR Value 33m
SYMBOL nmos 176 -144 R0
SYMATTR InstName M1
SYMATTR Value Si4490DY
SYMBOL e 224 -224 R90
SYMATTR InstName E1
SYMATTR Value 1
SYMBOL fra 112 -320 R90
SYMATTR InstName @1
SYMATTR SpiceLine delay=2.5m fstart=200 fend=6.4k oct=2 fcoarse=800 nmax=1 3 1k 3 1.01k 1 pp0=1 pp1=250m f0=400 f1=1.6K tavgmin=1m tsettle=500u
SYMBOL SpecialFunctions\\sample -112 352 R0
SYMATTR Value Vhigh=100
SYMATTR Value2 ref=8m
SYMATTR InstName A1
SYMBOL bv -336 288 R90
SYMATTR InstName B1
SYMATTR Value V=absdelay(V(Act,IN),100n)
SYMBOL bv -336 400 R90
SYMATTR InstName B2
SYMATTR Value V=V(IN,Rfb)
SYMBOL e 96 336 R0
SYMATTR InstName E2
SYMATTR Value 1
SYMBOL current 560 -448 R0
SYMATTR InstName ILOAD
SYMATTR Value PULSE(0 2 10u 500u 500u 1)