I'm trying to rebuild parts of the Microchip PICDEM FS USB board schematic partly as an experiment but mostly as a learning experience. There's a part of the circuit that appears to allow the device to auto-select between USB bus power and wall-brick power, that looks sort of like this:
NDS352P 1N5817 [VBUS>---+--+--[S G D]---->|--+-[+5V>
| | | | | | | | [VREG>---|--|-----|------->|--+ \ | \ 1N5817 100k / =.1uF / 33k \ | \ | | | +--+-----+--| GND
From what I read, NDS352P is a P-channel MOSFET. I also can't seem to locate this part on Allied, and didn't have any better luck with a couple of cross-references.
I'm thinking that this is an opportunity for me to learn about MOSFETs since I've never used one before. I only recently really learned about BJTs, and can only really keep it straight because, in general, only a small selection of the figures are relevant: hFE (the current gain Ib to Ic), which isn't crucial when used as a switch instead of an analog amplifier, Vce (voltage drop collector to emitter, i.e., how much less than Vcc is dropped across the output load), and max Ic (how much current can be passed through the load).
What are the important (analogous?) figures for a MOSFET? What features should I be looking for in a replacement for NDS352P?
Thanks PSM