P r o d u c t I n n o v a t i o n F r o m

PA91

6

PA91U

INPUT PROTECTION

AlthoughthePA91canwithstanddifferentialvoltagesupto±20V,

additional external protection is recommended. Low leakage, low

capacitance JFETs connected as diodes are recommended (e.g.

2N4416, Q1-Q4 in Figure 2).The differential input voltage will be

clampedto±1.4V.Thisissufficientoverdrivetoproducemaximum

powerbandwidth.

POWER SUPPLY PROTECTION

Unidirectionalzenerdiodetransientsuppressorsarerecommended

asprotectiononthesupplypins.SeeFigure2.Thezenersclamp

transientstovoltageswithinthepowersupplyratingandalsoclamp

powersupplyreversalstoground.Whetherthezenersareusedor

not,thesystempowersupplyshouldbeevaluatedfortransientper-

formanceincludingpower-onovershootandpower-offpolarityreversalsaswellaslineregulation.

Conditionswhichcancauseopencircuitsorpolarityreversalsoneitherpowersupplyrailshouldbeavoidedorpro-

tectedagainst.Reversalsoropensonthenegativesupplyrailisknowntoinduceinputstagefailure.Unidirectional

transzorbspreventthis,anditisdesirablethattheybebothelectricallyandphysicallyasclosetotheamplifieras

possible.

STAbILITY

ThePA91isexternallycompensatedandperformancecanbetailoredtotheapplication.Usethegraphsofsmall

signalresponseandpowerresponseasaguide.ThecompensationcapacitorCCmustberatedat500Vworking

voltage.AnNPOcapacitorisrecommended.ThecompensationnetworkCCRCmustbemountedcloselytothe

amplifierpins4and5toavoidspuriousoscillation.

QUIESCENT CURRENT REDUCTION

Whenpin3(IQ)isshortedtopin5(CC2)theABbiasingoftheoutputstageisdisabled.Thisraisesdistortionsince

theoutputstageisthenclassCbiased,butreducesthequiescentcurrentby1mAforapowerdissipationsavings

of0.4W.Pin3maybeleftopenifnotused.

–IN

+IN

Z1

Z2

11, 12

7, 8

1

2

6

PA91

Q1

Q2

Q3

Q4

FIGURE 2.

OVERVOLTAGE

PROTECTION

CONTACTINg CIRRUS LOgIC SUPPORT

ForallApexPrecisionPowerproductquestionsandinquiries,calltollfree800-546-2739inNorthAmerica.

Forinquiriesviaemail,pleasecontacttucson.support@cirrus.com.

InternationalcustomerscanalsorequestsupportbycontactingtheirlocalCirrusLogicSalesRepresentative.

Tofindtheonenearesttoyou,gotowww.cirrus.com

IMPORTANTNOTICE

CirrusLogic,Inc.anditssubsidiaries("Cirrus")believethattheinformationcontainedinthisdocumentisaccurateandreliable.However,theinformationissubject

tochangewithoutnoticeandisprovided"ASIS"withoutwarrantyofanykind(expressorimplied).Customersareadvisedtoobtainthelatestversionofrelevant

informationtoverify,beforeplacingorders,thatinformationbeingreliedoniscurrentandcomplete.Allproductsaresoldsubjecttothetermsandconditionsofsale

suppliedatthetimeoforderacknowledgment,includingthosepertainingtowarranty,indemnification,andlimitationofliability.NoresponsibilityisassumedbyCirrus

fortheuseofthisinformation,includinguseofthisinformationasthebasisformanufactureorsaleofanyitems,orforinfringementofpatentsorotherrightsofthird

parties.ThisdocumentisthepropertyofCirrusandbyfurnishingthisinformation,Cirrusgrantsnolicense,expressorimpliedunderanypatents,maskworkrights,

copyrights,trademarks,tradesecretsorotherintellectualpropertyrights.Cirrusownsthecopyrightsassociatedwiththeinformationcontainedhereinandgivescon-

sentforcopiestobemadeoftheinformationonlyforusewithinyourorganizationwithrespecttoCirrusintegratedcircuitsorotherproductsofCirrus.Thisconsent

doesnotextendtoothercopyingsuchascopyingforgeneraldistribution,advertisingorpromotionalpurposes,orforcreatinganyworkforresale.

CERTAINAPPLICATIONSUSINGSEMICONDUCTORPRODUCTSMAYINVOLVEPOTENTIALRISKSOFDEATH,PERSONALINJURY,ORSEVEREPROP-

ERTYORENVIRONMENTALDAMAGE(“CRITICALAPPLICATIONS”).CIRRUSPRODUCTSARENOTDESIGNED,AUTHORIZEDORWARRANTEDTOBE

SUITABLEFORUSEINPRODUCTSSURGICALLYIMPLANTEDINTOTHEBODY,AUTOMOTIVESAFETYORSECURITYDEVICES,LIFESUPPORTPROD-

UCTSOROTHERCRITICALAPPLICATIONS.INCLUSIONOFCIRRUSPRODUCTSINSUCHAPPLICATIONSISUNDERSTOODTOBEFULLYATTHECUS-

TOMER’SRISKANDCIRRUSDISCLAIMSANDMAKESNOWARRANTY,EXPRESS,STATUTORYORIMPLIED,INCLUDINGTHEIMPLIEDWARRANTIESOF

MERCHANTABILITYANDFITNESSFORPARTICULARPURPOSE,WITHREGARDTOANYCIRRUSPRODUCTTHATISUSEDINSUCHAMANNER.IFTHE

CUSTOMERORCUSTOMER’SCUSTOMERUSESORPERMITSTHEUSEOFCIRRUSPRODUCTSINCRITICALAPPLICATIONS,CUSTOMERAGREES,

BYSUCHUSE,TOFULLYINDEMNIFYCIRRUS,ITSOFFICERS,DIRECTORS,EMPLOYEES,DISTRIBUTORSANDOTHERAGENTSFROMANYANDALL

LIABILITY,INCLUDINGATTORNEYS’FEESANDCOSTS,THATMAYRESULTFROMORARISEINCONNECTIONWITHTHESEUSES.

CirrusLogic,Cirrus,andtheCirrusLogiclogodesigns,ApexPrecisionPower,ApexandtheApexPrecisionPowerlogodesignsaretrademarksofCirrusLogic,Inc.

Allotherbrandandproductnamesinthisdocumentmaybetrademarksorservicemarksoftheirrespectiveowners.