voltage source from 0 to 5

[Dummyeng]

hi
i built one circuit with lt3080
page 18 https://www.analog.com/media/en/technical-documentation/data-sheets/lt3080.pdf

but it doesnt work

i put 150 ohm load and test it
when i put second pot to zero it goes to 2v and i should turn first one until it goes to zero

but it is totally wrong because first one is for current

second question
is about lm2576 i like to have negative voltage https://e2e.ti.com/support/power-ma...negative-voltage-from-positive-buck-converter
but the output is only -1.2voltage for more info i put tomorrow schematic


in the end any idea for 0 to 5 volt 0.5A(zero is important)

 

[barry]

Maybe you have an assembly error?

 

[FvM]

You are talking about page 18 "lab supply" circuit? I presume it can work well.

Regarding inverting LM2576 operation, I've often used this configuration. -1.2 V output sounds like you have LM2576-ADJ version with 1.2 V reference voltage. You can add a reference voltage divider to get higher negative output. I don't know how the question is related to 0 to 5 V regulation problem?

What's your specification, just 0 to 5 V or also current regulation? How much output current?

 

[Dummyeng]

i connect lt3080 set pin to gnd but vout is 2V but it is opamp how it is possible

about lm 2576 with lm317 i get 0 voltage i try two structure i think one of them must be correct cause i was in hurry

 

[D.A.(Tony)Stewart]

The Diode looks backwards on your schematic to get -0.7V , but for preload to work to 0V Vo needs a load current below this. Use 1k to -10V.

 

[Easy peasy]

you need a delayed start circuit for this topology - and a source that cab supply about 3A for at least 10mS:

second question
is about lm2576 i like to have negative voltage
but the output is only -1.2voltage for more info i put tomorrow schematic

--- Updated Monday at 4:40 AM ---