I've got some issues making a 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)

The project is powered from DC\DC converter (Converts to 5V from batteries) and SIM800L directly without the mosfet. The SIM800L will power up nicely and connects itself to the network with 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: https://www.infineon.com/dgdl/irf540n.pdf?fileId=5546d462533600a4015355e396cb199f

  • 2
    \$\begingroup\$ Can you draw a schematic of how this stuff is hooked up? \$\endgroup\$ – ThreePhaseEel Aug 8 '17 at 1:42
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    \$\begingroup\$ Mind this part of the datasheet: "The power supply range of SIM800L is from 3.4 V to 4.4 V.Recommended voltage is 4.0 V." \$\endgroup\$ – Bence Kaulics Aug 8 '17 at 16:37
  • \$\begingroup\$ Can you use a scope to record the voltage/current when powering on with MOSFET? As @BenceKaulics noted, your voltage is probably too high. \$\endgroup\$ – LShaver Aug 8 '17 at 19:33

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