Version 4 SHEET 1 1944 840 WIRE 336 -80 240 -80 WIRE 432 -80 336 -80 WIRE 528 -80 432 -80 WIRE 688 -80 528 -80 WIRE 1104 -80 688 -80 WIRE 240 -64 240 -80 WIRE 336 -64 336 -80 WIRE 432 -64 432 -80 WIRE 528 -64 528 -80 WIRE 736 -32 720 -32 WIRE 816 -32 800 -32 WIRE 976 -32 816 -32 WIRE 1312 -32 976 -32 WIRE 1536 -32 1376 -32 WIRE 976 0 976 -32 WIRE 240 32 240 16 WIRE 336 32 336 0 WIRE 432 32 432 0 WIRE 688 64 688 -80 WIRE 816 64 816 -32 WIRE 416 112 400 112 WIRE 528 112 528 16 WIRE 528 112 496 112 WIRE 560 112 528 112 WIRE 976 112 976 64 WIRE 976 112 944 112 WIRE 1104 112 1104 -80 WIRE 464 192 448 192 WIRE 560 192 528 192 WIRE 1056 192 944 192 WIRE 560 272 544 272 WIRE 976 272 976 176 WIRE 976 272 944 272 WIRE 1104 272 1104 208 WIRE 1104 272 976 272 WIRE 1264 272 1104 272 WIRE 1312 272 1264 272 WIRE 1424 272 1392 272 WIRE 1440 272 1424 272 WIRE 1536 272 1536 -32 WIRE 1536 272 1520 272 WIRE 1584 272 1536 272 WIRE 1680 272 1584 272 WIRE 1584 288 1584 272 WIRE 1680 288 1680 272 WIRE 1264 304 1264 272 WIRE 464 352 448 352 WIRE 560 352 544 352 WIRE 1056 352 944 352 WIRE 1104 384 1104 368 WIRE 1264 384 1264 368 WIRE 1584 384 1584 352 WIRE 1680 384 1680 368 WIRE 352 432 272 432 WIRE 464 432 432 432 WIRE 560 432 464 432 WIRE 1424 432 1424 272 WIRE 1424 432 944 432 WIRE 272 448 272 432 WIRE 464 448 464 432 WIRE 560 512 544 512 WIRE 1536 512 1536 272 WIRE 1536 512 944 512 WIRE 272 528 272 512 WIRE 464 528 464 512 WIRE 1536 528 1536 512 WIRE 688 576 688 560 WIRE 816 576 816 560 WIRE 544 624 544 512 WIRE 1536 624 1536 608 WIRE 1536 624 544 624 WIRE 1632 624 1536 624 WIRE 1728 624 1712 624 FLAG 1104 384 0 FLAG 272 528 0 FLAG 816 576 0 FLAG 1584 384 0 FLAG 1680 384 0 FLAG 240 32 0 FLAG 1680 272 OUT FLAG 240 -80 IN FLAG 1264 384 0 FLAG 688 576 0 FLAG 448 192 0 FLAG 544 272 0 FLAG 448 352 0 FLAG 1728 624 0 FLAG 720 -32 0 FLAG 400 112 0 FLAG 336 32 0 FLAG 432 32 0 FLAG 464 528 0 SYMBOL nmos 1056 112 R0 SYMATTR InstName Q1 SYMATTR Value Si7370DP SYMBOL nmos 1056 272 R0 WINDOW 0 91 32 Right 2 WINDOW 3 172 66 Right 2 SYMATTR InstName Q2 SYMATTR Value Si7370DP SYMBOL schottky 960 0 R0 SYMATTR InstName D1 SYMATTR Value MBRS140 SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 960 112 R0 SYMATTR InstName C1 SYMATTR Value .1µ SYMBOL res 512 -80 R0 SYMATTR InstName R1 SYMATTR Value 1Meg SYMBOL res 448 416 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 20K SYMBOL cap 256 448 R0 SYMATTR InstName C2 SYMATTR Value 2200p SYMBOL schottky 1248 368 M180 WINDOW 0 24 72 Left 2 WINDOW 3 20 1 Left 2 SYMATTR InstName D2 SYMATTR Value MBRS1100 SYMATTR Description Diode SYMATTR Type diode SYMBOL ind 1296 288 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L1 SYMATTR Value 15µ SYMATTR SpiceLine Rpar=2K SYMBOL res 1424 288 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R3 SYMATTR Value 10m SYMBOL res 560 336 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 49.9K SYMBOL cap 528 176 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value .002µ SYMBOL cap 1568 288 R0 WINDOW 3 36 33 Left 2 WINDOW 123 26 60 Left 2 SYMATTR Value 33µ SYMATTR Value2 x3 SYMATTR InstName C4 SYMBOL voltage 240 -80 R0 WINDOW 3 25 101 Left 2 SYMATTR Value 36 SYMATTR InstName V1 SYMBOL diode 1376 -48 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D3 SYMATTR Value 1N4148 SYMBOL PowerProducts\\LT3845 752 304 R0 SYMATTR InstName U1 SYMBOL res 1520 624 M180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R5 SYMATTR Value 143K SYMBOL res 1728 608 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 16.2K SYMBOL cap 800 -48 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C5 SYMATTR Value 1µ SYMBOL res 512 96 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 82.5K SYMBOL res 1664 272 R0 SYMATTR InstName Rload SYMATTR Value 1.92 SYMBOL cap 320 -64 R0 SYMATTR InstName C6 SYMATTR Value 47µ SYMBOL cap 416 -64 R0 SYMATTR InstName C7 SYMATTR Value 2.2µ SYMBOL cap 448 448 R0 SYMATTR InstName C8 SYMATTR Value 100p TEXT 1592 464 Left 2 !.tran 2m startup TEXT 920 -96 Bottom 2 ;LT3845 - High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency\nHigh Voltage Telecom Step-Down Regulator\nInput: 20V to 55V Output: 12V @ 6.25A TEXT 248 640 Left 2 ;Note:\n A smaller value Css capacitor is used to reduce simulation time. Typical value should be 1500pF.\n If the simulation model is not found please update with the "Sync Release" command from the "Tools" menu.\n It remains the customer’s responsibility to verify proper and reliable operation in the actual application.\n Component substitution and printed circuit board layout may significantly affect circuit performance or reliability.\n Contact your local sales representative for assistance. This circuit is distributed to customers only for use with LTC parts.\n Copyright © 2012 Linear Technology Inc. All rights reserved.