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Topic: P-channel MOSFET for 5v circuit (Read 245 times) previous topic - next topic

largin

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)?

Thanks

larryd

#1
Jan 20, 2021, 03:15 am Last Edit: Jan 20, 2021, 03:17 am by larryd
" I need to drive a 2A 5V module with an Arduino."

What module ?

Why can't you can use a relay ?

Be more descriptive about the project.



Show us a good schematic of your circuit. 
Give links to components.
Posting images: 
https://forum.arduino.cc/index.php?topic=519037.0



No technical PMs.
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largin

" I need to drive a 2A 5V module with an Arduino."

What module ?

Why can't you can use a relay ?

Be more descriptive about the project.




Show us a good schematic of your circuit.  
Give links to components.
Posting images:  
https://forum.arduino.cc/index.php?topic=519037.0




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.

larryd

#3
Jan 20, 2021, 04:11 am Last Edit: Jan 20, 2021, 04:13 am by larryd
Lots of small DPDT 5v relays.








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largin

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.

larryd

#5
Jan 20, 2021, 05:30 am Last Edit: Jan 20, 2021, 05:34 am by larryd
No, it's not impossible, just think you should keep relays in mind.




We need to see more information on what you are 'exactly' trying to do.

Draw a schematic of what you are wanting.



Here are some examples showing how to control loads:






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MarkT

#6
Jan 20, 2021, 02:40 pm Last Edit: Jan 20, 2021, 02:40 pm by MarkT
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.
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

raschemmel

Quote
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...
Finally something to kill time during the shutdowns...

wvmarle

The IRLML6401 works for me. Hard to find something that's even smaller than that (SOT-23 package). Rated up to 4.3A.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

ShermanP

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.

MarkT

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.
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

largin

SMD parts had not even crossed my mind! That will work perfectly of course! Thanks guys and for the part numbers since there are so many to find!

larryd

#12
Jan 21, 2021, 01:45 am Last Edit: Jan 21, 2021, 01:48 am by larryd
No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

JohnRob

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.


Please do not PM me with thread based messages.  If your thoughts are worth responding,  the group should benefit from your insight.

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