I am using an LM2596 module with my project because it has a good efficiency and a stable output voltage.

My question is about the potentiometer found in the module.

  • Does it select the output voltage value what ever the input is, or does it just select the output related to input?
  • So if I set the output to 5v with 12v input will it change if I give 9v input with resetting the potentiometer?

closed as off-topic by Wesley Lee, Edgar Brown, RoyC, Bimpelrekkie, Finbarr Feb 18 at 15:01

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  • 1
    \$\begingroup\$ It should be absolute. That's the point of a regulator. \$\endgroup\$ – Unimportant Feb 7 at 17:06
  • \$\begingroup\$ i've seen a cheap one that did vary quite a bit with different input voltages, but most are fixed. \$\endgroup\$ – dandavis Feb 7 at 18:34

Short answer, the output voltage will not change.

  • I have quite a few of the LM2596 modules and upon testing them with different volatge ranges I found out that the input voltage must be at lest 1V to 1.5V greater than the output voltage.
  • If the above is not true (i.e. the input voltage is not large enough) the module's output will be almost equal to the input just a little bit less.
  • Also, I found out that on increasing the input voltage quite a lot the output seems to increase by about 0.1V. For example, If while setting the ouput of the module, the input is 12V and output is adjusted to 5V then if you will power the module afterwards with 20V than the output will be 5.1V.
  • So, it is better to adjust the output voltage when it is connected to the actual power supply.

The potentiometer sets the output voltage. It is measured against a fixed reference generated inside the LM2596 IC.

The output voltage should not change when you change the input voltage

There are limits, of course.

If you put 379Vdc on the input, then your "output" will most likely be a "bang" and a "RUD" (rapid unscheduled disassembly.)

If the input voltage is too low, then the output won't be at its set voltage, either.

The output voltage in most buck regulators needs to be a little higher than the output. I can't find a minimum difference in the datasheet, but all of the charts show at least 1V between input and output voltage (as far as I can see from the drawings.)

Its absolute maximum input is given as 40V.

So, if your input stays between about 6V and 40V, then your output will stay at the 5V level you set.


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