PWM to Analog converter circuit

Soldato
OP
Joined
13 Jul 2009
Posts
7,168
Location
Llanelli
Good thinking....checks email.

FQP27P06.

P-Channel QFET® MOSFET -60V, -27A, 70mΩ

This P-Channel enhancement mode power MOSFET is produced using Fairchild Semiconductor’s proprietary planar stripe and DMOS technology. This advanced MOSFET technology has been especially tailored to reduce on-state resistance, and to provide superior switching performance and high avalanche energy strength. These devices are suitable for switched mode power supplies, audio amplifier, DC motor control, and variable switching power applications.

They are about 90p each and so are much more expensive than the B772.

I would like to point out that I picked this one only because of low RDS(on) and logic level and was just an experiment. If I'd spent longer researching I may have found a better component for the job.

As an aside the later versions of the Phanteks PWM hub use a D1M1425 P-ch Mosfet which is also logic level and has an even lower RDS(on) of 14mΩ.

I was trying to minimise voltage drop across the transistor and have less heat. A lot of the specifications of components are beyond my comprehension having never really studied electronics design properly. ;)
 
Last edited:
Associate
Joined
28 Jan 2015
Posts
12
Good thinking....checks email.

FQP27P06.



They are about 90p each and so are much more expensive than the B772.

Well, if I can drive double amount of fans with a single circuit, and therefore save on the other components and also save space, those are 90p well spent ;)

I would like to point out that I picked this one only because of low RDS(on) and logic level and was just an experiment. If I'd spent longer researching I may have found a better component for the job.

As an aside the later versions of the Phanteks PWM hub use a D1M1425 P-ch Mosfet which is also logic level and has an even lower RDS(on) of 14mΩ.

I was trying to minimise voltage drop across the transistor and have less heat. A lot of the specifications of components are beyond my comprehension having never really studied electronics design properly. ;)

I will probably buy some similar MOSFETs in the next future and try to do some tests. I still need to make a PWM generator as I don't want to test directly on a PC. A way to read the RPMs would also be nice. Perhaps an "Arduino fan tester" can be a nice project for my next holidays.

PS: I also want to search for a variable resistor in other format, but I think last time I looked I didn't find anything rated 1/2W or more in another format.

PPS: can't find ANYTHING about D1M1425 ...
 
Soldato
OP
Joined
13 Jul 2009
Posts
7,168
Location
Llanelli
Sorry it is actually DTM4425. My eyesight isn't what it used to be.

Ooh that's a nice idea for an Arduino project. Might make one for myself. I have a great display for rpm and duty cycle.

There are rheostats out there and will cover several watts but they are a lot more expensive. It's generally better to use low power potentiometers and amplify using transistors.
 
Last edited:
Associate
Joined
28 Jan 2015
Posts
12
That DTM4425 have good RDS value but is terrible at disipating heat, it makes pretty clear why all my Phanteks hubs have died.

For what I see, and if I'm not misunderstanding anything, seems our best bets without breaking the 1 poound barrier, are the FQP27P06 and the IRF4905PBF, or AOI403 if we can lose some power for the best RDS value.

If price is not a problem, seems like SUP90P06-09L-E3 is a wonderful part for this project and could handle cooling for a small nuclear plant. Also , the older version of this ones can be found in China much cheaper than standard mouser /digikey / ... prices, I think only difference is not leadfree pins.

PS: I totally forgot about what you said about the potentiometers. Yeah, I see I need no more watt handling on the trimmer now, dunno why I was convinced I needed more in the past...
 
Last edited:
Back
Top Bottom