I understand from the datasheet that the switching clock can be controlled by applying a clock to the Mode (sync) input. I cannot confirm this with simulation in LTspice. The internal clock does not track the externally applied clock - nor does the clkout. Am I doing something wrong?
| Version 4 SHEET 1 1848 740 WIRE 64 -80 -32 -80 WIRE 208 -80 64 -80 WIRE 432 -80 208 -80 WIRE -32 -64 -32 -80 WIRE 208 -64 208 -80 WIRE 64 0 64 -80 WIRE 112 0 64 0 WIRE 432 0 432 -80 WIRE 432 0 400 0 WIRE 64 16 64 0 WIRE 432 16 432 0 WIRE -32 32 -32 16 WIRE 64 96 64 80 WIRE 112 96 64 96 WIRE 432 96 432 80 WIRE 432 96 400 96 WIRE 64 112 64 96 WIRE 432 112 432 96 WIRE 32 192 0 192 WIRE 112 192 96 192 WIRE 544 192 400 192 WIRE -96 288 -144 288 WIRE 112 288 -96 288 WIRE -144 352 -144 288 WIRE -16 384 -48 384 WIRE 112 384 64 384 WIRE 432 384 400 384 WIRE 544 384 544 192 WIRE 544 384 512 384 WIRE 656 384 544 384 WIRE 752 384 656 384 WIRE 848 384 752 384 WIRE 544 400 544 384 WIRE 656 400 656 384 WIRE 752 400 752 384 WIRE 848 400 848 384 WIRE -144 464 -144 432 WIRE 32 480 0 480 WIRE 112 480 96 480 WIRE 544 480 400 480 WIRE 656 480 656 464 WIRE 656 480 544 480 WIRE 544 496 544 480 WIRE 752 496 752 464 WIRE 848 496 848 480 WIRE 304 560 304 544 WIRE 208 592 208 544 WIRE 544 592 544 576 WIRE 208 608 208 592 FLAG 304 560 0 FLAG -48 384 0 FLAG -32 32 0 FLAG 0 192 0 FLAG 752 496 0 FLAG 544 592 0 FLAG 848 496 0 FLAG 848 384 OUT FLAG -32 -80 IN FLAG 64 112 0 FLAG 432 112 0 FLAG 0 480 0 FLAG -144 464 0 FLAG 208 592 clko FLAG -96 288 sync SYMBOL res 80 368 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 40k SYMBOL voltage -32 -80 R0 SYMATTR InstName V1 SYMATTR Value 24 SYMBOL cap 96 208 M270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName C2 SYMATTR Value 1µ SYMBOL ind 416 400 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L1 SYMATTR Value 3.3µ SYMATTR SpiceLine Rser=10m SYMBOL cap 736 400 R0 SYMATTR InstName C4 SYMATTR Value 47µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.002 Lser=0 mfg="TDK" pn="C4532X5ROJ47@M" type="X5R" SYMBOL res 528 384 R0 SYMATTR InstName R2 SYMATTR Value 1Meg SYMBOL res 528 480 R0 SYMATTR InstName R3 SYMATTR Value 243K SYMBOL cap 640 400 R0 SYMATTR InstName C5 SYMATTR Value 4.7p SYMBOL res 832 384 R0 SYMATTR InstName Rload SYMATTR Value 1 SYMBOL cap 48 16 R0 SYMATTR InstName C6 SYMATTR Value 1µ SYMBOL cap 416 16 R0 SYMATTR InstName C7 SYMATTR Value 1µ SYMBOL cap 96 496 M270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName C1 SYMATTR Value 1n SYMBOL PowerProducts\\LT8640S 256 240 R0 SYMATTR InstName U2 SYMBOL voltage -144 336 R0 WINDOW 3 -110 234 Left 2 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(0 3 0 1n 1n {1/(2*900k)} {1/(900k)}) SYMATTR InstName V2 TEXT 704 576 Left 2 !.tran 750u startup |
