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I want to create a power switch (on/off) for a hot-swap plug-in module that connects to my (future) PCB.

Got a MCU on board and a single 3.3V supply, fed from AA batteries with through a DC/DC, this is the supply VCC I also want to switch to the plug-in module. I went with a P-channel MOSFET so I can do high-side switching ('cutting' the VCC instead of the return ground to the module).

Question is: which P-MOSFET I should choose that will allow working with such a low voltage on the Vgs side? and also - will I need a BJT for 'pushing' the gate or I can connect the gate of the PMOS directly to the MCU logic IO pins?

Notes: 1. I am on a budget since this card will be going to mass-production so I need the lowest component count possible + cheapest & smallest possible parts. 2. I won't be needing more than 200mA fed to the plug-in module.

Your help is much appreciated. Thanks

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There are many "logic Level" MOSFETs available, so you're in good stead if you choose one of those from someone like IR. SInce you are going into production you'd do better asking for spot pricing from your suppliers.

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  • \$\begingroup\$ OK, do you believe this will do the trick?ec.irf.com/v6/en/US/adirect/… (IRF IRLML2244TRPBF) I can connect it's gate directly to the MCU IO pin? \$\endgroup\$ – mindbomb Oct 28 '12 at 10:17
  • \$\begingroup\$ Rds(on) will be around 60 mOhm at Vgs = -3.3 @ 60 mA you get 2.4 mW dissipation in device. All looks good. \$\endgroup\$ – placeholder Oct 28 '12 at 15:05

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