80C51便携式产品中的低功耗设计

C-DC变换器，可以实现单键开关机、自动关机、禁止关机、定时开机等功能。
　　
　　现在，越来越多的电池变换芯片具有SHUTDOWN引脚和电流与负载断开的功能。采用这一特性实现的电路，使用与图2类似的原理，关机电流也可以达到1μA以下。
　　
　　
　　
　　keateenagerthanatwelveyearold,yet,Stevewentunnoticed...untilMissWhite.MissWhitewasasmiling,young,beautifulredhead,andStevewasinlove!Forthefirsttimeinhisyounglife,hecouldn’ttakehiseyesoffhisteacher;yet,stillhefailed.Heneverdidhishomework,andhewasalwaysintroublewithMissWhite.Hisheartwouldbreakunderhersharpwords,andwhenhewaspunishedforfailingtoturninhishomework,hefeltjustmiserable!Still,hedidnotstudy.Inthemiddleofthefirstsemesterofschool,theentireseventhgradewastestedforbasicskills.Stevehurriedthroughhistests,andcontinuedtodreamofotherthings,asthedayworeon.Hisheartwasnotinschool,butinthewoods,whereheoftenescapedalone,tryingtoshutoutthesights,soundsandsmellsofhisalcoholichome.Noonecheckedonhimtoseeifhewassafe.Nooneknewhewasgone,becausenoonewassoberenoughtocare.Oddly,Stevenevermissedadayofschool.Oneday,MissWhite’simpatientvoicebrokeintohisdaydreams.“Steve!!”Startled,heturnedtolookather.“Payattention!”StevelockedhisgazeonMissWhitewithadolescentadoration,asshebegantogooverthetestresultsfortheseventhgrade.“Youalldidprettywell,”shetoldtheclass,“exceptforoneboy,anditbreaksmyhearttotellyouthis,but...”Shehesitated,pinningStevetohisseatwithasharpstare,hereyessearchinghisface.“...Thesmartestboyintheseventhgradeisfailingmyclass!”ShejuststaredatSteve,astheclassspunaroundforagoodlook.Stevedroppedhiseyesandcarefullyexaminedhisfingertips.Afterthat,i

《80C51便携式产品中的低功耗设计(第4页)》