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I've got a circuit board with a D2PAK NMOS pad that I need to find a mosfet that will work with a raspberry pi's 3.3V GPIO. This is the current one I'm using and it isn't working well. https://www.digikey.ca/product-detail/en/infineon-technologies/IRLZ34NSTRLPBF/IRLZ34NSTRLPBFCT-ND/2441092

Trying to find one on digikey with a drive voltage of 2.5V is almost impossible (unless I'm doing something wrong)

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  • \$\begingroup\$ If you're driving it with a 3.3V GPIO, why do you need a drive voltage of 2.5V? \$\endgroup\$
    – TimWescott
    Commented Feb 10, 2019 at 23:31
  • \$\begingroup\$ Because of Stackexchange rules, someone's going to come along and say this question isn't suitable because you're asking for specific product recommendations. I suggest you change your question to "what parameters would an N-channel FET need to do this job?" \$\endgroup\$
    – TimWescott
    Commented Feb 10, 2019 at 23:32
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    \$\begingroup\$ The MOSFET you linked has a threshold voltage of 2.0V or less and is specified for Vgs as low as 2.5V. So, this transistor will work with a 3.3V logic signal. You need to show us a schematic of your actual circuit, describe what you want the circuit to do, and describe what the circuit is actually doing. \$\endgroup\$ Commented Feb 10, 2019 at 23:40
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    \$\begingroup\$ What does not working well mean? \$\endgroup\$
    – sstobbe
    Commented Feb 10, 2019 at 23:48
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    \$\begingroup\$ That's because the "Drive Voltage" in the Digikey terms is not what you should be looking at. Look at Vgs(th) max; then you'll find a lot of options! The Drive voltage is the voltage at which the manufacturer tested its part, it doesn't necessarly means that it won't work if not tested exactly at the wanted value. \$\endgroup\$ Commented Feb 11, 2019 at 2:03

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This isn't a shopping question, it is a question about using the digikey search and reading FET datasheets, so it shouldn't be closed IMO.

Usually a MOSFET datasheet will specify its guaranteed max RdsON at a specified Vgs or over a range of Vgs. This is from the one in your question:

enter image description here

Max RdsON is specified over a range of Vgs. This is important, when you drive a FET with a specific Vgs you must pick a part with a RdsON spec at this Vgs (or lower Vgs).

VgsTH spec is not useful for switching applications. At Vgs=VgsTH the FET only begins to conduct, but if you want it to be fully turned on you will need a higher Vgs... but the VgsTH spec does not say how much. If you pick a FET with VgsTH below 3V3 then it will turn on at Vgs=3V3 but you don't know what RdsON it will have at that drive voltage. It may turn on fully, or just a little. This is probably the reason why your FET does not work well.

On the other hand, you can be absolutely sure this FET will switch fine with 3V3 gate drive, because its max RdsON is specified at Vgs=2.5V.

enter image description here

The "drive voltage" field in DigiKey search engine specs "Drive Voltage (Max Rds On, Min Rds On)" which means this is the voltage range for which RdsON is guaranteed in the datasheet.

So I checked every "drive voltage" between 0.9 and 3V (use shift key to select a range) and got lots of choices. You'll want to refine that, select packages you want, sort by price or RdsON, etc.

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    \$\begingroup\$ +1 Vgs(th) is typically specified at 250uA, which isn't turned on very much at all. \$\endgroup\$ Commented Dec 21, 2019 at 23:08
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    \$\begingroup\$ Yeah, VgsTH is useful for making MOSFET audio amps. Not for switching. \$\endgroup\$
    – bobflux
    Commented Dec 21, 2019 at 23:14
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You may want to at this similar part from Vishay/Siliconix: SIHL630STRL-GE3

You can find this part at Mouser at $1.32 each. The part data sheet shows the following typical output characteristics on the left below. As compared to the your current part on the right it is apparent that Vishay is willing to show the characteristics for lower gate drive voltage.

enter image description here

An even more interesting part is this ROHM part also at Mouser: RSJ301N10FRA

At a price over $2.00 each it is more pricey that the other but it shows significantly more current at saturation with a 2.5V gate drive. It may be a better choice for your application but make sure to review the data sheet to make sure other parameters are suitable.

enter image description here

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  • \$\begingroup\$ I don't see that your suggested part is any better than the original. Note that the y-axis range is different on the two graphs, and the step size for the Vgs curves is different. It appears to me that both devices saturate at about 5A with a Vgs of 3V. \$\endgroup\$ Commented Feb 11, 2019 at 0:36
  • \$\begingroup\$ I'll agree that the parts are very similar with higher gate drives. On the other hand the Vishay/Siliconix part is willing to show curves for 2.25V at a drain current of 300mA which is what the OP says is his load. \$\endgroup\$ Commented Feb 11, 2019 at 0:44
  • \$\begingroup\$ @ElliotAlderson - I added a second part that shows significantly higher current capability at the 2.5V gate drive. This may be better for the OP. \$\endgroup\$ Commented Feb 11, 2019 at 0:58

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