Hello,
I need to drive a 2A 5V module with an Arduino. The module is connected to a common ground and I can't change that part, so I only have the positive side.
I've seen old threads with logic-level MOSFETS but they're no longer available, there's one that's still sold but I'd rather invest in something that could be replaced down the line. It seems P-channel MOSFETS are quite rare, even more so for logic level.
So what would be my options here? Is there a way to use a normal MOSFET without access to more than 5V, say with a MOSFET driver (I don't know much about these)? Or if I use a step-up converter for example, can I still safely drive a 5V circuit with a 12V gate (and which MOSFET in that case)?
I could use a relay but there is not much space, I would have to modify the box so if I could do it with MOSFET or smaller it would be best. It's to control a entertainment system, which consumes around 1-1.5A, and I'm already using Arduino to control some functions, but I want to be able to cut the power off totally too. Due to the construction finding the ground cable would require too much modification. But it can be seen as a black box in this case I think.
It's not as small as a MOSFET, and even flatter solid state relays are very expensive. Is it really impossible with a MOSFET? I also wanted to learn about it in the process. But relay will have to do if it's impossible.
largin:
It seems P-channel MOSFETS are quite rare, even more so for logic level.
Not rare at all, there are thousands, but there are tens of thousands of n-channel power MOSFETs so they look
rare by comparison. For instance currently Farnell list 2858 lines of p-channel power MOSFET and
12385 lines of n-channel power MOSFET. For Mouser I see 2979 and 15485...
What you will find is that vast majority of the logic-level p-channel devices are surface mount,
since modern manufacturer avoids through-hole wherever possible due to the extra costs involved.
Another SOT-23 is the DMP1045U (12V) or DMP2045U (20V). And if you want a TO-220 package, there's the ever-popular NDP6020P. I think all of these will be available for a long time.
Will you be switching the 5V module supply from a 5V Arduino? If so, you can probably drive the mosfet gate directly from a GPIO pin, with a 100R resistor in series. If driving from a 3.3V Arduino, you'll need an intermediate little N-channel or NPN to shift the voltage. A drawing might let us see how you want to rig it up.
BTW you choose a MOSFET by its on-resistance rather than current maximum - you would never want to
be anyway even near the max current rating, since that assumes maximal heatsinking and maximum junction
temperature, both of which are well worth avoiding.
So if you want less than 0.25W dissipation for a 3A load, choose a MOSFET with on-resistance at
or below 0.25 / 3^2 = 27 milliohm.
P Channel Mosfets are not going obsolete. They are less common than N-channel because they require an extra layer of doping compared to an N-Channel. This is because silicon is intrinsically N material.
So they cost more, do not perform as well as N-Channel making them less attractive for most applications.
For a 4.3 amp load you need at least a 10A device. Not knowing your packaging constraints I would suggest you look at something like: IRF7420TRPBF
I found this at Digikey using their filtering capability (really great). I specified I needed:
P-Channel
Continuous drain current of 10A and above
Active part (ie not obsolete)
Be careful you have a thermal path from the Mosfet to the ambient air.
You can reduce the thermal load if you use a more capable Mosfet like SIS407DN-T1-GE3
Very Important
You can only put 5V on the MosFet gate (because you only have 5v. A gate voltage of 5V will not result in a resistance as quoted at the top of the data sheet. You will have to go to the graphs.
Another question: Is your load powered by 5V? If not there are likely more options.
