www.ti.com SNAS094D – APRIL 1995– REVISED MARCH 2013 ...

1 APRIL1995 REVISEDMARCH2013LM1972 Pot2-Channel78dBAudioAttenuatorwithMuteC heckforSamples:LM19721 FEATURESDESCRIPTIONTheLM1972isa digitallycontrolled2-channel78dB2 3-WireSerialInterfaceaudioattenuatorfabr icatedonaCMOS process. 104dBMuteAttenuation0dB , 78dB, PopandClickFreeAttenuationChangesattenua tioncurvecanbecustomizedthroughsoftwaret ofit Potisdemonstratedthrough AutomatedStudioMixingConsolesitsexcellen tSignal-to-NoiseRatio,extremelylow MusicReproductionSystems(THD+N), Pot SoundReinforcementSystemscontainsa mutefunctionthatdisconnectstheinputsigna lfromtheoutput,providingaminimum ElectronicMusic(MIDI) 's3-wireserialdigitalinterfaceisTTLKEYSP ECIFICATIONSandCMOS compatible;receivingdatathatselectsa TotalHarmonicDistortion+ (max)OutpinoftheLM1972allowsmultiple Potstobedaisy-chainedtogether,reducingth enumberof Frequencyresponse:100kHz( 3dB)(min)enableanddatalinestoberoutedfor agiven Attenuationrange( ):78dB(typ) Differentialattenuation: (max) Signal-to-noiseratio( Vrms):110dB(min) Channelseparation:100dB(min) TopViewCircuitSeeDWPackage1 Pleasebeawarethatanimportantnoticeconcer ningavailability,standardwarranty,anduse in 1995 2013, APRIL1995 (1)(2)(3)SupplyVoltage(VDD VSS)15 VVoltageatAnyPinVSS + (4)150mWESDS usceptabiIity(5)2000 VJunctionTemperature150 CSolderingInformationDWPackage(10sec.)

2 +260 CStorageTemperature 65 C to+150 C(1)AllvoltagesaremeasuredwithrespecttoG NDpins(1,3,5,6,14,16,19),unlessotherwise specified.(2) a goodindicationofdeviceperformance.(3)If Military/Aerospacespecifieddevicesarereq uired,pleasecontacttheTexasInstrumentsSa lesOffice/Distributorsforavailabilityand specifications.(4)Themaximumpowerdissipa tionmustbederatedatelevatedtemperaturesa ndis dictatedbyTJMAX, JA, andtheambienttemperatureTA. Themaximumallowablepowerdissipationis PD= (TJMAX TA)/ JAorthenumbergivenin theAbsoluteMaximumRatings,whicheveris ,TJMAX= +150 C,andthetypicaljunction-to-ambienttherma lresistance,whenboardmounted,is65 C/W.(5)Humanbodymodel,100pFdischargedthr ougha (1)(2)TMINTATMAXT emperatureRangeTMIN TA TMAX0 C TA +70 CSupplyVoltage(VDD VSS) (1)AllvoltagesaremeasuredwithrespecttoGN Dpins(1,3,5,6,14,16,19),unlessotherwises pecified.(2) a 1995 2013, APRIL1995 REVISEDMARCH2013 ElectricalCharacteristics(1)(2)Thefollow ingspecificationsapplyforallchannelswith VDD= +6V,VSS= 6V,VIN= ,andf = 1 kHz, 25 (Limits)Typical(3)Limit(4)ISSupplyCurren tInputsareACGrounded24mA(max)THD+NTotalH armonicDistortionplusNoiseVIN= @ 78dBSNRS ignal-to-NoiseRatioInputsareACGrounded@ 12dBAttenuation120110dB(min)A-WeightedAM MuteAttenuation10496dB(min)AttenuationSt epSizeError0dBto (max) 48dBto 78dB @ (min)Attenuation@ (min)Attenuation@ (min)Attenuation@ (min)Channel-to-ChannelAttenuationAttenu ation@0dB, 20dB, 40dB, 60dB (max)TrackingErrorAttenuation@ 78dB (max) (max)RINACI nputImpedancePins4,20,VIN= ,f = 1 kHz4020k (min)60k (max)IINI nputCurrent@Pins9,10,11@0V< VIN< (max)Data-OutLevels(Pin12)VDD=6V,VSS= (max) (min)(1)Allvoltagesaremeasuredwithrespec ttoGNDpins(1,3,5,6,14,16,19),unlessother wisespecified.

3 (2) a goodindicationofdeviceperformance.(3)Typ icalsaremeasuredat25 C andrepresenttheparametricnorm.(4)Limitsa respecifiedtoTexasInstrument's AOQL(AverageOutputQualityLevel).Copyrigh t 1995 2013,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback3 ProductFolderLinks:LM1972LM1972 SNAS094D APRIL1995 (3,19):Eachinputhasitsownindependentgrou nd, (4,20):Thereare2 independentsignalinputs, (2,17):Thereare2 independentsignaloutputs, (13,15):Positivevoltagesupplypins, (7,18):Negativevoltagesupplypins,VSS1and VSS2. Tobetiedtogroundin a (1,5,6,14,16):Thesefivepinsarenotphysica llyconnectedtothediein anyway( ,Nobondwires). , (8):Digitalsignalgroundfortheinterfaceli nes;CLOCK,LOAD/SHIFT, (9):Theclockinputacceptsa (10):Theload/shiftinputacceptsa theenablepinofthedevice,allowingdatatobe clockedin whilethisinputis low(0V).Data-In(11):Thedata-ininputaccep tsa usedtoacceptserialdatafroma microcontrollerthatwillbelatchedanddecod edtochangea channel' (12):Thispinis usedin daisy-chainmodewheremorethanone Potis clockedintothechainfromthe C,theprecedingdatain theshiftregisteris shiftedouttheDATA-OUTpintothenext Potin thechainortogroundif it is thelast Potin 1995 2013, APRIL1995 REVISEDMARCH2013 ConnectionDiagramCopyright 1995 2013,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback5 ProductFolderLinks:LM1972LM1972 SNAS094D APRIL1995 VSS= KHzbyFFTVDD VSS= 1995 2013, APRIL1995 REVISEDMARCH2013 TypicalPerformanceCharacteristics(contin ued)THD+ N vsFrequencyandAmplitudeFFTof1 + + NTHD+ 1995 2013,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback7 ProductFolderLinks:LM1972LM1972 SNAS094D APRIL1995 PotisshowninFigure16.

4 Thisattenuationstepscheme,however, constantlogarithmicattenuationschemeof1d Bstepsfora panningfunctionasshowninFigure17. Theonlyrestrictiontothecustomizationofat tenuationschemesarethegivenattenuationle velsandtheircorrespondingdatabitsshownin Table1. ,theattenuationlevelwillbechangedcorresp ondingtothedatabitsshowninTable1. AsshowninFigure19, anLM1972canbeconfiguredasa ( ) 1995 2013, APRIL1995 REVISEDMARCH2013LM1972 ChannelAttenuationvsDigitalStepValue( ) Potis constantata nominal40k . ToeliminateanyunwantedDCcomponentsfrompr opagatingthroughthedeviceit is commontouse1 F notnecessary,however, , Potvariestypicallybetween25k and35k Potismadeupofa resistorladdernetworkwitha logarithmicattenuation, ,a Potcannotbeconsideredasalinearpotentiome ter,butcanbeconsideredonlyasa shouldbenotedthatthelinearityofa Potcannotbemeasureddirectlywithouta bufferbecausetheinputimpedanceofmostmeas urementsystemsis ,theoutputofthe ,a Potis Potis itsabilitytomutetheinputsignaltoanattenu ationlevelof104dBasshowninFigure16.

5 Thisis accomplishedinternallybyphysicallyisolat ingtheoutputfromtheinputwhilealsogroundi ngtheoutputpinthroughapproximately2 k .Copyright 1995 2013,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback9 ProductFolderLinks:LM1972LM1972 SNAS094D APRIL1995 (to11111111) mutebuttonontohissystemwhichcouldcausea microcontrollertosendtheappropriatedatat oa ,thedesignerhasa Potwasdesignedtobeusedasanattenuatorfors ignalswithintheaudiospectrum, bufferattheoutputofthe Pot, shouldalsoberememberedthattheoutputbuffe r'ssupplyvoltagedoesnothavetobethesameas the Pot' 3-wireserialcommunicationformatthatis easilycontrolledbya ,comprisedofDATA-IN,CLOCK,andLOAD/SHIFTi s showninFigure3. Figure3, theLOAD/SHIFT lineis bitsforchannelselectionand8 ,theMSBis sentfirstandthe8 bitsofaddressdataaretobesentbeforethe8 :LSBA ddressRegister(Byte0)00000000 Channel100000001 Channel200000010 Channel3 DataRegister(Byte1) : : : : :: : : : : :: : : : : :: :10 SubmitDocumentationFeedbackCopyright 1995 2013, APRIL1995 (continued) ( mute ) ( mute ): : : : :: ( mute ) ( mute ) PotSYSTEMARCHITECTUREThe Pot'sdigitalinterfaceisessentiallya shiftregister,whereserialdataisshiftedin ,latched, shiftedintotheDATA-INpin,thepreviouslyla tcheddatais ,theLOAD/SHIFT linegoeshigh, continuedeachandeverytimeanattenuationch angeis updated,only,whenthatchannelis selectedforanattenuatorchangeorthesystem is Potis poweredup,eachchannelis placedintothemutedmode.

6 PotLADDERARCHITECTUREE achchannelofa , theladderconsistsofmultipleR1 Table1. It canbeseeninFigure21thattheinputimpedance forthechannelis a constantvalueregardlessofwhichtapswitchi s selected, PotLadderArchitectureDIGITALLINECOMPATIB ILITYThe Pot'sdigitalinterfacesectionis compatiblewitheitherTTLorCMOS logicduetotheshiftregisterinputsactingup ona thresholdvoltageof2 1995 2013,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback11 ProductFolderLinks:LM1972LM1972 SNAS094D APRIL1995 availablefordaisy-chainsystemconfigurati onswheremultiple , ,theDATA-OUTpinshouldbeterminatedthrough a 2 k resistorif ,however, PotSystemArchitectureDAISY-CHAINCAPABILI TYS incethe Pot'sdigitalinterfaceisessentiallya shiftregister,multiple Figure24, forann- Potdaisy-chain, Potsasit isforone ,thenthedataisclockedinsequentiallywhile theprecedingdataineach PotisshiftedouttheDATA-OUTpintothenext Potinthechainortogroundif it is thelast.

7 Latchingthedataintoeachoftheircorrespond ing (channelselection)andtheappropriatetapsw itchcontrollingtheattenuationlevelis Potasshownin theTypicalPerformanceCharacteristicswaso btainedbyplacinga is importanttobesurethatthesignallevelbeing measuredisofthesamefrequencysuchthata ,toensureanaccuratemeasurement,themeasur edchannel'sinputshouldbeACgroundedthroug ha 1 F 1995 2013, APRIL1995 REVISEDMARCH2013 CLICKSANDPOPSSo,whyisthatoutputbuffernee dedanyway?Therearethreeanswerstothisques tion,allofwhichareimportantfroma buffer/amplifierattheoutputofa Potis toensurethattherearenoaudibleclicksorpop sduetoattenuationstepchangesin anon-boardbipolaropamphadbeenusedfortheo utputstage,itsrequirementofa finiteamountofDCbiascurrentforoperationw ouldcausea DCvoltage pop whentheoutputimpedanceofthe ,thisphenomenonis duetothefactthattheoutputimpedanceofthe Potis changingwithstepchangesanda bipolaramplifierrequiresa ,sodoestheDCbiascurrentandthusthereis a DCvoltage pop.

8 Secondly,the Pothasnodrivecapability,soanydesiredgain needstobeaccomplishedthrougha ,theoutputofa Potneedstoseea JFET inputbufferprovidesa highinputimpedancetotheoutputofthe lownoisefloorandlowTHD+ Potis capableofbeingusedin thefeedbackloopofanamplifier,however,ass tatedpreviously,theoutputofthe Potneedstoseea highimpedancein , , a Potusedinthefeedbackloopcreatesa , ,however,becauseofthe Pot'sversatilitythegaincanbecontrolledth roughprogrammingsuchthattheclippinglevel ofthesystemis thatwheninmutemodetheinputis ,thusresultingin ,a PotDaisy-ChainedCircuitCopyright 1995 2013,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback13 ProductFolderLinks:LM1972LM1972 SNAS094D APRIL1995 (March2013)toRevisionDPage 1995 2013,TexasInstrumentsIncorporatedProduct FolderLinks:LM1972 PACKAGE OPTION 1 PACKAGING INFORMATIONO rderable DeviceStatus(1)Package TypePackageDrawingPinsPackageQtyEco Plan(2)Lead/Ball Finish(6)MSL Peak Temp(3)Op Temp ( C)Device Marking(4/5)SamplesLM1972 MLIFEBUYSOICDW2036 TBDCall TICall TI0 to 70LM1972 MLM1972M/NOPBACTIVESOICDW2036 Green (RoHS& no Sb/Br)CU SNLevel-3-260C-168 HR0 to 70LM1972 MLM1972MX/NOPBACTIVESOICDW201000 Green (RoHS& no Sb/Br)CU SNLevel-3-260C-168 HR0 to 70LM1972M (1) The marketing status values are defined as follows:ACTIVE: Product device recommended for new : TI has announced that the device will be discontinued, and a lifetime-buy period is in : Not recommended for new designs.

9 Device is in production to support existing customers, but TI does not recommend using this part in a new : Device has been announced but is not in production. Samples may or may not be : TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substancedo not exceed by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI mayreference these types of products as "Pb-Free".RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS : TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold.

10 Antimony trioxide basedflame retardants must also meet the <=1000ppm threshold requirement. (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuationof the previous line and the two combined represent the entire Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finishvalue exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided.