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LT3465 model problems in LT SWcadiii

Discussion in 'CAD' started by No spam, Nov 22, 2005.

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  1. No spam

    No spam Guest

    I am having trouble shutting off the device using the CTRL pin.

    I used the LT3465 model in the SWcadiii program and accompanying circuitry
    based on the app note for the part, i.e. 22uH inductor, etc. On the output,
    I use one LED with 4.3 ohms resistance to ground. When ground is applied to
    the CTRL pin, should I expect the part to shut off? The data sheet implies
    this, but I do not see what I think I should. I would expect very low input
    current to the part (probably u-amps) and negligible voltage/current to the
    output LED. Instead, the output appears on. I use a 5V input. In CAD, I
    have ramping the CTRL pin from 0 to supply voltage and at no point does the
    part appear to shut off.

    I am seeing similar behavior on the bench. Am I missing something or doing
    something wrong? Is supply voltage an issue?
     

  2. Hello John,

    The LT3465(A) works as promised in the datasheet.
    I don't know your circuit but a correct one like my example
    performs very well. The output current can be controlled from
    0mA to about .2V/Rsense with a control voltage from 0 to 1V.
    Above 1V the current stays at .2V/Rsense.

    Copy the text attached at the end of this message into a file
    named with a postfix ".asc", e.g. test.asc

    This schematic file can be then opened with LTspice.
    Then press RUN , walk to the coffee machine to get a
    hopefully free coffee and when you come back the simulation is done.

    Best regards,
    Helmut
    Moderator of the LTspice Yahoo group
    http://groups.yahoo.com/group/LTspice




    The LTspice schematic file test.asc .



    Version 4
    SHEET 1 880 680
    WIRE -304 144 -304 80
    WIRE -304 496 -304 224
    WIRE -304 528 -304 496
    WIRE -160 80 -304 80
    WIRE -160 208 -160 80
    WIRE -160 240 -160 208
    WIRE -160 496 -304 496
    WIRE -160 496 -160 304
    WIRE -96 368 -96 336
    WIRE -96 496 -160 496
    WIRE -96 496 -96 448
    WIRE -64 80 -160 80
    WIRE -64 336 -96 336
    WIRE 0 208 -160 208
    WIRE 0 336 -64 336
    WIRE 64 80 16 80
    WIRE 64 128 64 80
    WIRE 144 496 -96 496
    WIRE 144 496 144 416
    WIRE 224 128 224 80
    WIRE 304 80 224 80
    WIRE 336 80 304 80
    WIRE 336 160 336 80
    WIRE 352 336 288 336
    WIRE 352 336 352 288
    WIRE 352 384 352 336
    WIRE 352 496 144 496
    WIRE 352 496 352 464
    WIRE 368 160 336 160
    WIRE 368 288 352 288
    WIRE 464 160 432 160
    WIRE 464 288 432 288
    WIRE 560 160 528 160
    WIRE 560 288 528 288
    WIRE 560 288 560 160
    WIRE 656 80 336 80
    WIRE 656 208 656 80
    WIRE 656 496 352 496
    WIRE 656 496 656 272
    FLAG -304 528 0
    FLAG -64 336 ctrl
    FLAG 304 80 out
    SYMBOL ind -80 96 R270
    WINDOW 0 32 56 VTop 0
    WINDOW 3 5 56 VBottom 0
    SYMATTR InstName L1
    SYMATTR Value 22µ
    SYMBOL voltage -304 128 R0
    SYMATTR InstName V1
    SYMATTR Value 5
    SYMBOL diode 368 176 R270
    WINDOW 0 32 32 VTop 0
    WINDOW 3 0 32 VBottom 0
    SYMATTR InstName D1
    SYMATTR Value LED
    SYMBOL diode 464 176 R270
    WINDOW 0 32 32 VTop 0
    WINDOW 3 0 32 VBottom 0
    SYMATTR InstName D2
    SYMATTR Value LED
    SYMBOL diode 432 304 M270
    WINDOW 0 32 32 VTop 0
    WINDOW 3 0 32 VBottom 0
    SYMATTR InstName D4
    SYMATTR Value LED
    SYMBOL diode 528 304 M270
    WINDOW 0 32 32 VTop 0
    WINDOW 3 0 32 VBottom 0
    SYMATTR InstName D5
    SYMATTR Value LED
    SYMBOL res 336 368 R0
    SYMATTR InstName R1
    SYMATTR Value 10
    SYMBOL cap 640 208 R0
    SYMATTR InstName C1
    SYMATTR Value 0.22µ
    SYMBOL cap -176 240 R0
    SYMATTR InstName C2
    SYMATTR Value 1µ
    SYMBOL voltage -96 352 R0
    WINDOW 3 -37 170 Left 0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V2
    SYMATTR Value PWL(0 1.5 .1m 1.5 .85m 0 1.25m 0 2m 1.5 )
    SYMBOL PowerProducts\\LT3465A 144 272 R0
    SYMATTR InstName U1
    TEXT -328 -48 Left 0 !.model LED D(Is=1e-24 N=2 Rs=5)
    TEXT -328 -16 Left 0 !.tran 2m
    TEXT 112 -48 Left 0 ;Watch I(LED) and V(ctrl)
     
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