Version 4 SHEET 1 1680 680 WIRE 416 -128 272 -128 WIRE 544 -128 464 -128 WIRE 608 -128 544 -128 WIRE 720 -128 688 -128 WIRE 768 -128 720 -128 WIRE 864 -128 768 -128 WIRE 416 -112 416 -128 WIRE 464 -112 464 -128 WIRE 544 -112 544 -128 WIRE 768 -112 768 -128 WIRE 864 -112 864 -128 WIRE -640 -16 -832 -16 WIRE -48 -16 -640 -16 WIRE 416 -16 416 -32 WIRE 416 -16 -48 -16 WIRE 464 -16 464 -32 WIRE 544 -16 464 -16 WIRE 608 -16 544 -16 WIRE 720 -16 720 -128 WIRE 720 -16 688 -16 WIRE 768 -16 768 -48 WIRE 864 -16 864 -32 WIRE -832 0 -832 -16 WIRE -640 0 -640 -16 WIRE 416 0 416 -16 WIRE 544 0 544 -16 WIRE -48 32 -48 -16 WIRE -16 32 -48 32 WIRE 144 32 48 32 WIRE 272 32 272 -128 WIRE -48 64 -48 32 WIRE 144 80 144 32 WIRE -832 96 -832 80 WIRE 416 96 416 80 WIRE -640 112 -640 80 WIRE -640 112 -752 112 WIRE -224 112 -640 112 WIRE 224 112 112 112 WIRE -752 144 -752 112 WIRE -640 144 -640 112 WIRE 720 144 720 -16 WIRE -528 176 -560 176 WIRE -416 176 -448 176 WIRE -224 176 -416 176 WIRE 368 176 112 176 WIRE -976 224 -1008 224 WIRE -832 224 -896 224 WIRE -800 224 -832 224 WIRE -560 240 -560 176 WIRE -224 240 -560 240 WIRE 176 240 112 240 WIRE 272 240 272 128 WIRE 272 240 256 240 WIRE 416 240 416 192 WIRE 416 240 272 240 WIRE 432 240 416 240 WIRE 528 240 512 240 WIRE -832 256 -832 224 WIRE -416 256 -416 176 WIRE -752 272 -752 240 WIRE -640 272 -640 224 WIRE -640 272 -752 272 WIRE -1008 288 -1008 224 WIRE -320 304 -336 304 WIRE -224 304 -240 304 WIRE 128 304 112 304 WIRE 224 304 208 304 WIRE -640 320 -640 272 WIRE -416 336 -416 320 WIRE -832 352 -832 336 WIRE -224 368 -288 368 WIRE 224 368 112 368 WIRE 720 368 720 224 WIRE 720 368 224 368 WIRE -288 384 -288 368 WIRE 720 384 720 368 WIRE -1008 400 -1008 368 WIRE -144 432 -144 416 WIRE -48 432 -48 416 WIRE 48 432 48 416 WIRE -288 464 -288 448 WIRE 720 480 720 464 FLAG 528 240 0 FLAG -144 496 0 FLAG -48 432 0 FLAG 48 432 0 FLAG -336 304 0 FLAG -288 464 0 FLAG -832 96 0 FLAG 544 64 0 FLAG 544 -48 0 FLAG 720 480 0 FLAG 864 -16 0 FLAG 768 -16 0 FLAG 864 -128 OUT FLAG -832 -16 IN FLAG -416 336 0 FLAG 144 80 0 FLAG -640 320 0 FLAG -832 352 0 FLAG -1008 400 0 SYMBOL LTC3721-1 -48 240 R0 SYMATTR InstName U1 SYMBOL nmos 224 32 R0 WINDOW 0 52 26 Left 2 WINDOW 3 51 55 Left 2 SYMATTR InstName Q1 SYMATTR Value IRF7201 SYMBOL nmos 368 96 R0 WINDOW 3 55 65 Left 2 SYMATTR Value IRF7201 SYMATTR InstName Q2 SYMBOL res 416 256 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R1 SYMATTR Value 75m SYMBOL res 272 224 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 100 SYMBOL cap -160 432 R0 WINDOW 3 30 52 Left 2 SYMATTR Value 270p SYMATTR InstName C1 SYMBOL res -432 160 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 100K SYMBOL res -224 288 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 100K SYMBOL cap -304 384 R0 WINDOW 3 30 52 Left 2 SYMATTR Value .1µ SYMATTR InstName C2 SYMBOL voltage -832 -16 R0 WINDOW 3 26 92 Left 2 SYMATTR Value 12 SYMATTR InstName V1 SYMBOL ind2 400 -128 R0 WINDOW 0 -5 37 Right 2 WINDOW 3 -4 74 Right 2 SYMATTR InstName L1 SYMATTR Value 1µ SYMATTR Type ind SYMBOL ind2 400 -16 R0 WINDOW 0 -2 36 Right 2 WINDOW 3 -7 75 Right 2 SYMATTR InstName L2 SYMATTR Value 1µ SYMATTR Type ind SYMBOL ind2 480 -128 M0 WINDOW 0 -4 38 Right 2 WINDOW 3 -4 71 Right 2 SYMATTR InstName L3 SYMATTR Value 4µ SYMATTR Type ind SYMBOL ind 592 -112 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L4 SYMATTR Value 20µ SYMBOL ind 592 0 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L5 SYMATTR Value 20µ SYMBOL schottky 528 -48 M180 WINDOW 0 34 61 Left 2 WINDOW 3 35 16 Left 2 SYMATTR InstName D1 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 528 64 M180 WINDOW 0 34 53 Left 2 WINDOW 3 38 13 Left 2 SYMATTR InstName D2 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 704 128 R0 SYMATTR InstName R5 SYMATTR Value 15.8K SYMBOL res 704 368 R0 SYMATTR InstName R6 SYMATTR Value 5K SYMBOL cap 208 368 M180 WINDOW 0 24 64 Left 2 WINDOW 3 27 14 Left 2 SYMATTR InstName C3 SYMATTR Value .001µ SYMBOL res 224 288 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 50K SYMBOL cap 752 -112 R0 SYMATTR InstName C4 SYMATTR Value 100µ SYMBOL res 848 -128 R0 SYMATTR InstName Rload SYMATTR Value 10 SYMBOL cap -432 256 R0 WINDOW 3 30 52 Left 2 SYMATTR Value 1µ SYMATTR InstName C5 SYMBOL cap 48 16 R90 WINDOW 3 -1 -14 VBottom 2 WINDOW 0 0 35 VBottom 2 SYMATTR Value 1µ SYMATTR InstName C6 SYMBOL res -656 -16 R0 SYMATTR InstName R8 SYMATTR Value 10k SYMBOL res -656 128 R0 SYMATTR InstName R9 SYMATTR Value 10k SYMBOL nmos -800 144 R0 SYMATTR InstName M1 SYMATTR Value BSS123 SYMBOL res -880 208 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R10 SYMATTR Value 100 SYMBOL res -816 352 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R11 SYMATTR Value 100k SYMBOL voltage -1008 272 R0 WINDOW 3 26 92 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR Value 0 SYMATTR InstName V2 TEXT 368 -160 Left 2 !K1 L1 L2 L3 1 TEXT 400 424 Left 2 !.tran 15m startup TEXT 744 360 Left 2 ;Feedback PD=1.2V max TEXT -1048 448 Left 2 ;Control via uC, High to turn OFF TEXT -264 544 Left 2 ;Frequency @Ct ~250kHz\nTherefore switching F ~125kHz