芯片英文简介

74LS161DatasheetGeneralDescriptionThesesynchronous,presettablecountersfeatureaninternalcarrylook-aheadforapplicationinhigh-speedcountingdesigns.TheDM74LS161Aare4-bitbinarycounters.ThecarryoutputisdecodedbymeansofaNORgate,thuspreventingspikesduringthenormalcountingmodeofoperation.Synchronousoperationisprovidedbyhavingallflip-flopsclockedsimultaneouslysothattheoutputschangecoincidentwitheachotherwhensoinstructedbythecount-enableinputsandinternalgating.Thismodeofoperationeliminatestheoutputcountingspikeswhicharenormallyassociatedwithasynchronous(rippleclock)counters.Abufferedclockinputtriggersthefourflip-flopsontherising(positive-going)edgeoftheclockinputwaveform.Thesecountersarefullyprogrammable;thatis,theoutputsmaybepresettoeitherlevel.Aspresettingissynchronous,settingupalowlevelattheloadinputdisablesthecounterandcausestheoutputstoagreewiththesetupdataafterthenextclockpulse,regardlessofthelevelsoftheenableinput.TheclearfunctionfortheDM74LS161Aisasynchronous;andalowlevelattheclearinputsetsallfouroftheflip-flopoutputsLOW,regardlessofthelevelsofclock,load,orenableinputs.(这些同步,预置表计数器为应用在高速计数功能内部携带有预见性的设计。DM74LS161A4比特二进制计数器。套利或非门的输出是通过解码,从而防止在正常峰值计数的操作模式。同步操作是由所有人字拖时钟同步,以便输出变化互相重合时,指示count-enable输入和内部控制。这种模式的操作消除了输出计数峰值通常与异步计数器(波纹时钟)。一个缓冲时钟输入触发四人字拖(正向的)边缘的时钟输入波形上升。这些计数器是完全可编程;也就是说,输出可以被预设的水平。作为预设定是同步的,建立一个低水平的负载输入禁用计数器,使输出后同意设置数据在下一个时钟脉冲，无论使输入的水平。DM74LS161A的明确的函数是异步的,明确的输入和低水平集的所有四个触发器输出低,无论级别的时钟,负载,或使输入。)OrderingCodeOrderNumberPackageNumberPackageDescriptionDM74LS161AMM16A16-LeadSmallOutlineIntegratedCircuit(SOIC),JEDECMS-012,0.150NarrowDM74LS161ANN16E16-LeadPlasticDual-In-LinePackage(PDIP),JEDECMS-001,0.300WideFunctionTable

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RecommendedOperatingConditionsSymbolParameterDM54LS161DM74LS161UnitsMiM\NomMaxMin\NomMaxVCCSupplyVoltage4555547555.25VVIHHighLevelInputVoltage22VVILLowLevelInputVoltage0.70.8VIOHHighLevelOutputCurrent-0.4mAIOLLowLevelOutputCurrent48mAfCLKClockFrequency(Note025025MHzClockFrequency(Note020020MHztWPulseWidth(Note1)Clock206206nsClear209209PulseWidth(Note2)Clock2525nsClear2525tSUSetupTime(Note1)Data208208nsEnableP25172517Load25152515SetupTime(Note2)Data2020nsEnableP3030Load3030tHHoldTime(Note1)Data0b30b3nsOthers0b30b3HoldTime(Note2)Data55nsOthers55tRELClearReleaseTime(Note2020nsClearReleaseTime(Note2)2525nsTAFreeAirOperatingTemperatureb55125070CSwitchingCharacteristicsSymbolParameterFrom(Input)To(Output)RL=2kUnitsSymbolParameterFrom(Input)To(Output)CL=15pFCL=50pFUnits

SymbolParameterFrom(Input)To(Output)MinMaxMinMaxUnitsfMAXMaximumClockFrequency2520MHztPLHPropagationDelayTimeLowtoHighLevelOutputClocktoRippleCarry2530nstPHLPropagationDelayTimeHightoLowLevelOutputClocktoRippleCarry3038nstPLHPropagationDelayTimeLowtoHighLevelOutputClockto加(LoadHigh)2227nstPHLPropagationDelayTimeHightoLowLevelOutputClockto曲(LoadHigh)2738nsPhysical