Data Sheet

Li+PIN
ThispinisinternallyconnectedtothepositiveterminaloftheLiPoconnector.Youcanconnecta
singlecellLiPo/LithiumIonoraDCsupplysourcetothispinforpoweringtheBoron.Remember
thattheinputvoltagerangeonthispinis3.6to4.2VDC.
FortheBoron2G/3Gversion,makesurethattheexternalDCsupplyisabletosupport2Apeak
currentrequirements.
3V3PIN
Thispinistheoutputoftheonboard3.3Vstep-downswitchingregulator(TorexXC9258A).The
regulatorisratedat1000mAmax.Whenusingthispintopowerotherdevicesorperipherals
remembertobudgetinthecurrentrequirementoftheBoronfirst.UnlikethePhoton,thispin
CANNOTbeusedtopowertheBoron.
ENPIN
TheENpinisnotapowerpin,perse,butitcontrolsthe3V3andcellularmodempowerviaaload
switch(XC8107,U2).TheENpinispulledhighbya100KresistortoPMIC_SYS(3.8V),whichis
poweredbyVUSB,themicroUSBconnector,ortheLiPobattery.Becausethepull-upcanresultin
voltagesabove3.3VyoushouldneverdirectlyconnectENtoa3.3VGPIOpin.Instead,youshould
onlypullENlow,suchasbyusinganN-channelMOSFETorotheropen-collectortransistor.
TheENpincanforcethedeviceintoadeeppower-downstatewhereitusesverylittlepower.It
alsocanusedtoassurethatthedeviceiscompletelyreset,similartounpluggingit,withone
caveat:
IfusingtheENpintodeeplyresetthedevice,youmustbecarefulnottoallowleakagecurrent
backintothenRF52MCUbyGPIOorbypull-upsto3V3.Ifyouonlypowerexternaldevicesby3V3
youwon'trunintothis,as3V3isde-poweredwhenENislow.
However,ifyouhavecircuitrythatispoweredbyaseparate,externalpowersupply,youmustbe
careful.AnexternallypoweredcircuitthatdrivesanRF52GPIOhighwhenENislowcanprovide
enoughcurrenttokeepthenRF52frompoweringdownandresetting.Likewise,apull-uptoan
externalpowersupplycandothesamething.Besurethatinnocircumstancescanpowerby
suppliedtothenRF52when3V3isde-powered.
Seethepowersupplyschematic,below,formoreinformation.