No spam said:
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?
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)
