PIC18 USB微控制器采用纳瓦技术的电源管理

Reducingpowerconsumptionisalwaysdesirablein

systemswhereresourcesmaybelimited.Thisis

particularlytrueinUSBsystems,wheredesignersmust

notonlyunderstandtherulesimposedbytheUSB

specification,butknowwhenandhowtousewhichof

theavailablepower-savingfeatures.

Thisapplicationnotediscusseswaystomanagepower

onthemembersofthePIC18familyofmicrocontrollers

withnanoWatttechnologyinUSBapplications.Inthis

document,wewillpresentasummaryoftheUSB

specificationinregardstopowermanagementanddis-

tributionandtodescribewhenandhowtouse

power-savingfeaturesinresponsetodifferentUSB

events.Wewillalsodiscusshowtheadvanced

power-savingfeaturesofenhancedPIC18deviceswith

nanoWatttechnologycanbeusedtomeetthesegoals.

OurfocusinthisdocumentisonPIC18devices

withtheUSBperipheralandusesthe

PIC18F2455/2550/4455/4550familyofmicro-

controllersasanexample.Allreferencestothedevice

datasheetinthisdocumentrefertothedatasheetfor

thisfamily(DS39632).AN950PowerManagementforPIC18USBMicrocontrollerswithnanoWattTechnologyAuthor:RawinRojvanitThisdiscussionislimitedtoUSBdevicesonlyandisnotintendedforaUSBhost.TheauthorassumesthattheMicrochipTechnologyInc.readershavesomebasicknowledgeabouttheUSBstandard.AllreferencestotheUSBspecificationinthisINTRODUCTIONdocumentreferto“USBSpecification