Issues powering SIM800L though a mosfet (IRF540N)

Thread Starter

Roy Niels

Joined Aug 7, 2017
Hey everybody I've got som issues making my SIM800L module to power up correctly through a mosfet.


- 2x LifePO4 batteries in serie (6.4V 1800mAh)
- 1x LM2596 DC Converter (Converts to 5V and able to peak at 3A)
- 1x SIM800L (Might has peaks of 2A)
- 1x IRF540N Mosfet (N-channel enhancement)

See upload for the setup.

Whenever I use these batteries, converter (Converts to 5V) and SIM800L directly without the mosfet it will power up nicely and connects itself to the network. I am able to do communication as expected.

But when I am adding the mosfet (which I wanna use to completely turn off the SIM800L) it stops working accordingly. I get power issues. Quick blinking of the LED and never connecting to the network.

I expect that the SIM800 is not drawing enough current to startup the way it is supposed to be. But according to the datasheet of the IRF540N it should be able to draw 10A at 5V. So I am a little bit puzzled why it is not working.

I added a cap. (10uF, Vcc to GND) right next to the SIM800L but that didn't make any difference.

Am I using the wrong mosfet for this kind of setup, or do I miss some theoretical knowledge and parts that inhibit this setup from working? Is the given continuous drain current not as straight away as I think it is?

Datasheet mosfet:

Other question:

I have a cheap bench power supply (CK3005DK, no specs online :S) that can supply 5A / 30V. But running at 5V it can only draw a limited amount of current (.7A if I was not mistaken). I was under the impression that a power supply could be limited to the voltage and draw more current if needed, but I guess I can't get it higher then a certain amperage with a voltage limit of 5V. Is this correct?

Which power supply would be a good alternative to get something that can adjust both voltage and current without being related to each other so I can test 5V and let it draw 2A when needed. I don't want to depend on my batteries for testing my prototype.

Kind regards,