Hi,
I need to control the power supply of a couple of devices at about 400mA. I’ve been looking at what is done on the MCB2300 from Kiel:
http://www.keil.com/mcb2300/mcb2300-schematics.pdf (page 3)
They use a mosfet to control the supply of the SD card. However, they do not interface the mosfet directly to the microcontroller, they use a bipolar in between…
Anybody could explain why? Any way to interface directly with a mosfet? I really want to keep the part number down.
Thanks!
Jean
look into logic level mosfets.
SpinDrah:
look into logic level mosfets.
Hi,
Thank you for the answer. How would you interface a logic level mosfet to a microcontroller?
Pull up connected to the source, source directly connected to output of the microntroller?
Thnaks!
My best guess is that the bipolar is there to create an open-collector output so they can swing the P-MOSFET from GND to 3.3v. At such low voltage levels, getting good rail-to-rail voltage is important. However, I would have thought they could have eliminated the bipolar and just used software to create an open-collector output. Voltage-low for the 2378 is only 0.18V which seems plenty low for that MOSFET.
I am a big fan of hte load switches available from Fairchild