Version 4.1
SHEET 1 968 680
WIRE -1344 -240 -1392 -240
WIRE -1152 -240 -1344 -240
WIRE -992 -224 -1088 -224
WIRE -832 -224 -992 -224
WIRE -1152 -208 -1232 -208
WIRE -1392 -176 -1392 -240
WIRE -992 -160 -992 -224
WIRE -1392 -32 -1392 -96
WIRE -1232 -16 -1232 -208
WIRE -1056 -16 -1232 -16
WIRE -992 -16 -992 -80
WIRE -992 -16 -1056 -16
WIRE -800 -16 -992 -16
WIRE -640 -16 -720 -16
WIRE -608 -16 -640 -16
WIRE -608 48 -608 -16
WIRE -992 64 -992 -16
WIRE -608 192 -608 128
WIRE -992 208 -992 144
FLAG -1392 -32 0
FLAG -992 208 0
FLAG -832 -224 Vout
FLAG -1056 -16 Vfb
FLAG -1344 -240 Vref
FLAG -608 192 0
FLAG -640 -16 Vdac
SYMBOL res -976 160 R180
WINDOW 0 -46 85 Left 2
WINDOW 3 -72 57 Left 2
SYMATTR InstName R1
SYMATTR Value 68.1k
SYMBOL res -1008 -176 R0
WINDOW 0 43 45 Left 2
WINDOW 3 43 73 Left 2
SYMATTR InstName R2
SYMATTR Value 620k
SYMBOL voltage -1392 -192 R0
WINDOW 0 43 41 Left 2
WINDOW 3 44 72 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName Vref
SYMATTR Value 0.8V
SYMBOL OpAmps\\opamp -1120 -160 M180
WINDOW 0 -3 111 Left 2
WINDOW 38 -2 31 Left 2
SYMATTR InstName U1
SYMATTR SpiceModel opamp1
SYMATTR Value opamp1
SYMBOL voltage -608 32 R0
WINDOW 0 43 41 Left 2
WINDOW 3 212 88 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName Vdac
SYMATTR Value {vdac}
SYMBOL res -704 -32 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 71 50 VBottom 2
SYMATTR InstName R3
SYMATTR Value 520k
TEXT -1264 -600 Left 2 ;SMPS - external DAC adjust
TEXT -1232 -552 Left 2 !.tran 20us
TEXT -1976 352 Left 2 !*  pin order      in- in+ out\n.SUBCKT OPAMP1      1  2   3\nEGAIN     3 0   2 1     1000K\n.ENDS
TEXT -1408 -312 Left 2 ;Power Supply
TEXT -992 -552 Left 2 !.step param Vo 9V 3V -1V
TEXT -992 -512 Left 2 !.param m=-1.216 b=9.056
TEXT -992 -472 Left 2 !.param vdac = (Vo - b ) / m
TEXT -1400 40 Left 2 ;Control Loop maintains Vfb = Vref
TEXT -792 -80 Left 2 ;External DAC adjustment
RECTANGLE Normal -864 256 -1472 -288 1