LM2576 Enable with ESP32 IO pin

[htekin42]

Hi everybody,

I am working on a project and I need to control a LM2576 voltage converter with ESP32 IO pin.
I made a design with optocoupler which is connected to enable pin of LM2576.
I am asking this question because I have never experienced this situation before.
We always connected the enable pin to ground because it is always enabled.
But we need enable and disable the LM2576 according to code running on ESP32.

Here is the schematic of my design.

Is it work or not?
what is your suggestions?

Thanks

 

[danadakk]

What is part number optocoupler ?

Should work fine, output of opto must meet -

Keep in mind the opto coupler inverts the logic, ESP32 pin high, lm2576 shutdown.


Regards, Dana.

 

[htekin42]

What is part number optocoupler ?

Should work fine, output of opto must meet -

View attachment 180553

Keep in mind the opto coupler inverts the logic, ESP32 pin high, lm2576 shutdown.


Regards, Dana.

Optocoupler is LTV-817-S, inverting logic what we want. In esp program, in a situation, it outputs high on one of pin and want to enable LM2576.

 

[danadakk]

I do not see a current drive to OpTo led R limiter......20 mA recommended.

Regards, Dana.

 

[KlausST]

Hi,

An optocoupler is a device for galvanic isolation. Since your circuit is not galvanically isolated you don´t need an optocoupler at all. If you need an external switching device then any BJT, digital transistor, or logic level MOSFET will do.

But indeed I don´t see the need of an external switching device.
Thus simply connect the ESP output to the ON/OFF input. Done.

Klaus

 

[danadakk]

You might investigate the ESP32 GPIO pin state during boot/power up. There may be
some considerations there about how to handle LM2576 to make sure its only on
under program control, if thats of concern.

This also may be indicative of need for opto coupler, eg. power sequencing, pullups or pull downs,
etc..


Regards, Dana.