Hi all,
Boring question I know, and probably not very important in any practical sense, but…
I was looking at the specs for Q1 (IRLML2246TRPbF p-channel mosfet) that is used for reverse polarity protection on the battery input of the April board, and it states the Vgs max is +/- 12V. So as I understand it, if Vbat > 12V, then Vgs >12 V and Q1 should fail, right?
The hardware page for the April board says: “April can operate from any DC voltage from 3.3 to 17 Volts, and tolerates voltages down to -12 Volts”.
Do I have this right, or is there some other consideration I am forgetting? I’ve been away from electronics for awhile and am having to relearn some things. If I am right, I guess this could be a problem if you were trying to run the imp on an April board using a 12V lead acid battery on a battery charger. Maybe…
Those are the parameters for the TPS62172 DCDC step down convertor, which would be the max for VIN or the USB port… but if the FET max is 12V, then you wouldn’t want to put more through the P+,P- pads.
Yep, this was an oversight on the original boards. I think the FET may have been changed on later boards (from adafruit, at least as they get stock from us) but one of the other guys might know for sure.
Thanks again for confirmation. I purchased my April board from Digikey. The markings on Q1 (the RP protection FET) say DMB and Z0 (rotated 90 deg ccw) as best as I can tell. I will try to check if that matches the IRL part number in the BoM.
EDIT: Well the marking does not seem to match the Int. Rectifier convention, so it is probably not a IR part, and definitely not the IRLML2246 specified in the BoM.
SECOND EDIT: Found it. Q1 on the April board is a Diodes Incorporated DMP3098L, which has Vds 30V max and Vgs 20V max, so it does satisfy the RP protection and Vin compatibility specs.
