What kind of mosfet can i use as a switch for a solenoid....with MSP430

Elo,

Try searching for a "logic level mosfet".  I have used some of these in the past (but unfortunately don't remember part numbers).  It is easy to find mosfets with thresholds in the 1.8 to 2.5 volt range that can handle way more current than you need.  The ones I used were around 50 to 60 amps.

Another option is to use a BJT transistor as a level shifter to control the gate on the mosfet if you use something with a higher threshold voltage.

Mike

Use BT136 TRIAC. It has a capability to hold 600V both A.C. and D. C.

It holds upto 4 Amp. of current. It can drive your solenoid easily. It is controlled by gate voltage.

Learn before use. It is on using gate voltage but get off only if supply off. It is slightly tricky.

You can use GTO(Gate Turn Off Thyristor) which can be turned off by gate voltage

-1 on the TRIAC idea.. they latch on and can only be turned off by removing power through them.

Go with a good logic-level MOSFET. Don't forget a reverse-biased diode across the coil though, otherwise turning off the solenoid will blow out the MOSFET from back-EMF in the coil inductance.

elo

Try FDC637BNZ

http://www.digikey.ca/product-search/en?x=26&y=17&lang=en&site=ca&KeyWords=FDC637BNZ

FDC637BNZ
N-Channel 2.5V Specified PowerTrench® MOSFET
20V, 6.2A, 24mΩ
Features
Max rDS(on) = 24mΩ at VGS = 4.5V, ID = 6.2A
Max rDS(on) = 32mΩ at VGS = 2.5V, ID = 5.2A

And don't forget to use 1N4001 for inductive clamp.

Peter

Brian Boorman said:

-1 on the TRIAC idea.. they latch on and can only be turned off by removing power through them.

SOme of them can be cleared. And since DC was mentioned, I guess the BT is one of them. However, IIRC it requires a negative voltage on the gate.

ST MIcros Alternistor and "snubberless" tree-quadrant TRIACs are specifically made for driving solenoids.

Brian Boorman said:

Go with a good logic-level MOSFET. Don't forget a reverse-biased diode across the coil though,

MOSFETs have an internal reverse-biased diode.

Jens-Michael Gross said:

MOSFETs have an internal reverse-biased diode.

Yes there are some MOSFETs that have diodes built-in, mostly used for speeding up the synchronous low-side switch in DC-DC converter applications. However, outside of those specific types of parts, the body diodes exist because of a PN junction between the substrate and the doped well the channel sits in. These junctions aren't designed to handle current and shouldn't be used for that.

Regardless, you are still putting the diode in the wrong place. The best place to put it is right across the two leads of the coil. This shunts the back-EMF voltage during coil turn-off to the Vf of the shunt diode and keeps the current in a small loop. If the product needs to meet EMI/EMC specs, this is the way to go.

As Power issue is considered if You don't want to use TRIAC than use High power

You Can use Any of these MOSFET:

TC4420 - 18Vmax, 6A output current,     by  Microchip

IRFP250 - 200V, 33Amp     by Fairchild

FDSS2407 - 62V 3.3Amp    by  Fairchild

vikas dabas said:

You Can use Any of these MOSFET:

TC4420 - 18Vmax, 6A output current,     by  Microchip

IRFP250 - 200V, 33Amp     by Fairchild

FDSS2407 - 62V 3.3Amp    by  Fairchild

Vikas, I have to disagree with your suggestions as none of the above parts are suitable.

TC4420 is a gate driver.

IRFP250 will typically only conduct 0.25mA at 3V gate

FDSS2407 is only guaranteed  to conduct 0.25mA at 3V gate.

Peter

Agreed.

As i personally use BT136 as told before and use relay which don't need all such knowledge.

Thanks for corrections.

Brian Boorman said:

These junctions aren't designed to handle current and shouldn't be used for that.

On all MOSFETs I've used so far, this (additional or implicite) reverse diode is present and capable of handling exactly the same current as the MOSFET will handle in forward direction. (in one case, it was 70A rated and 380A peak current).
Other FETS, like J-FETs, are different.

Brian Boorman said:

The best place to put it is right across the two leads of the coil.

Definitely. But we were talking about protecting the MOSFET, not about making best EM design.