SIM954 - Enceinte audio / Vidéo SRS - Free user manual and instructions

USER MANUAL SIM954 SRS

ThisStanfordResearchSystemsproductiswarrantedagainstdefectsinmaterialsandworkmanshipforaperiodofone(1)yearfromthedateofshipment.

Service

Forwarrantyserviceorrepair, thisproductmustbereturnedtoaStanfordResearchSystems authorizedservicefacility.ContactStanfordResearchSystemsoranauthorizedrepresentative beforereturningthisproductforrepair.

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Copyright ©StanfordResearchSystems, Inc., 2008–2015. All rights reserved.

StanfordResearchSystems, Inc.

1290-DReamwoodAvenue

Sunnyvale, CA94089 USA

Phone:[phone]•Fax:[phone]

www.thinkSRS.com•e-mail:[e-mail]

PrintedinU.S.A.Documentnumber9-01649-903

Contents

GeneralInformationiii

SafetyandPreparationforUse......iii

Notation......iii

Specifications......iv

1Operation1-1

1.1QuickStart....1-2

1.2OperationInsidetheSIM900Mainframe......1-2

1.3OperationUsinganExternalPowerSupply.....1-3

1.4Interfaces....1-4

2Generalproperties2-1

2.1DCCharacteristics....2-2

2.2ACCharacteristics....2-4

2.3Noise 2-8

2.4Crosstalk ......2-9

2.5Isolation 2-10

2.6PowerSupplyandThermalConsiderations .....2–12

3Applicationnotes

3-1

3.1 ResistiveLoads....3-2

3.2CapacitiveLoadHandling.... 3-3

3.3 Inductive Loads....3-5

3.4 Transformers 3-8

3.5LoadImpedanceMatchingExamples...... 3–10

3.6BridgeConfiguration....3-11

3.7 Typical Application: a High Voltage Isolated, Low Noise, DC-DCConverter.... 3–12

3.8 Common Mode EMI/EMF 3-16

3.9OverdriveBehavior....3-18

3.10 Miscellaneous Loads 3-20

4Calibration

4-1

4.1 Getting Ready 4-1

4.2 Offset Voltage and Input Bias Current 4-1

5Circuitry5-1

5.1 CircuitDescription....5-2
5.2PartsLists....5-4
5.3SchematicDiagrams....5-7

GeneralInformation

TheSIM954300MHzAmplifier, partofStanfordResearchSystems' SmallInstrumentationModulesfamily, isadual, inverting, precision widebandamplifierwithupto±10Voutputvoltageand1Aoutput current.

Themodule can be used to drivemany types of light laboratory loads which exceed the capacity of typical instrument outputs without imposing the limitations and cost of typical high-power RF amplifiers.

SafetyandPreparationforUse

Thefront-panelBNCsareallgroundedtoEarthground,thepowerline-outletground,andthemetalchassisofthemodule.NodangerousvoltagesaregeneratedbytheSIM954.However,ifadangerous voltageisexternallyappliedtothemodule,itmaybepresentonall BNCconnectors,thechassis,theSIMinterfaceconnector,andmay causeinjuryordeath.

TheSIM954isasingle-widemodule designed to be used inside the SIM900Mainframe. Donotturnonthepower until themodule is completely inserted into themainframe and locked in place.

Specifications

PerformanceCharacteristics

PropertyMinTypMaxRemarks
Gain-4(12dB)3%max.gainererror
-3dBBandwidth300MHz smallsignal
GainFlatness1dBDCtogainpeak
Crosstalk			-60dB	at1MHz
			-40dB	fullBW
VSWR		1.2:1		DCto100MHz
		1.6:1		DCto300MHz
Isolation		-70dB		Output to input DC to 1MHz
		-40dB		Output to input DC to 300MHz
SlewRate	4000V/μs
OutputAmplitude	10V			into50Ω
Peak Output Current	1A			into ≤ 7Ω
AverageOutputCurrent	500mA			onechannelorsumofbothchannels
OutputImpedance		3.3Ω
InputImpedance		50Ω
InputOffsetVoltage			1mV	usertrimmable
InputBiasCurrent			10μA	usertrimmable
OperatingTemperature	0		40°C
Power Supply Voltages		-15 V,+15 V
Supply Current			±1 A	Internally current limited

Table1: SIM954Specifications

1Operation

Followingisashortoverviewongeneralguidelinesfortheoperation oftheSIM954.

InThisChapter

1.1QuickStart....1-2
1.2OperationInsidetheSIM900Mainframe.....1-2
1.3OperationUsinganExternalPowerSupply.....1-3
1.4Interfaces....1-4
1.4.1SIMInterfaceConnector......1-4
1.4.2DirectInterfacing....1-4

1.1QuickStart

TheSIM954containstwomostlyindependent,identicalsmallRF power amplifiers with a gain of -4 (12dB) into 50Ω and a -3dB bandwidth of 300MHz. The output voltage limit of ±10V can be achieved with a modest ±2.5V input voltage, so most test equipment candriveaSIM954channeltoitsvoltageandpowerlimits.

Themodulewasspecificallydesignedtodrivelaboratoryloadslike magneticcoils,capacitors,piezoelectricandelectrochemicalcells, smallmotors,heatersetc..Whiletheseloadsoftenrequirecurrents andvoltagesbeyondtherangeofmanytestinstruments,driving themwithexpensiveandbulkypoweramplifiersgenerallydoesnot representasatisfactoryandefficientsolution.

Unlikemanypoweramplifiers, the SIM954 can operate as a precise DC amplifier, wideband RF amplifier and driver stage for difficult passive loads like ceramic capacitors and high Qresonant circuits. It will stay unconditionally stable under a variety of load conditions, and its specifications will deteriorate in a predictable manner.

Thetwootherwiseindependentamplifierchannelsshareacommion powersupplyandarelimitedbythetotalpowerconsumptionpermissibleforasinglewideSIMmodule.Seesection2.6onpage2-12forfurtherdiscussion.

1.2OperationInsidetheSIM900Mainframe

TheSIM954isprimarilydesignedtoworkinsideaSIM900mainframe.UnlikeallotherSIMmodules,however,theSIM954mayundercertaincircumstancesbe"hot-plugged"intoanoperatingSIM900 mainframeunderpower.TheSIM954containsuniquepower-oncircuitrytosupportstand-aloneoperation.Thiscircuitry,however, interfereswiththeSIM900powersupply'ssoft-startdesign. Asa result,onlytwoSIM954modulescanreliablybeturnedonwithin aSIM900. Anallowablework-aroundtothisistofirstturnonthe SIM900mainframe,andthen"hotplug"additionalSIM954modules intovacantslotsoftheSIM900,onebyone. Thisprocedureisonly recommendedfortheSIM954,andmaynotbeusedwithanyotherSIM module.

Becauseoftheirhighercurrentrequirements,thenumberofSIM954 operatedinasingleSIM900mainframeshouldbelimitedtoamaximumoffour.Themodulesshouldbeseparatedbyatleastoneslot fromeachother,andanyothermodulenexttoaSIM954shouldnot haveanincreasedpowerconsumptionitself.

SIMmoduleswithhigherpowerconsumption,liketheSIM965Ana-

logFilterandtheSIM940RubidiumFrequencyStandard,shouldnot beoperatednexttoaSIM954.

Runningatitspowerlimit,aSIM954canheatuptoapproximately 50^ C.SomelowpowerSIMmodulesliketheSIM928BatteryIsolated VoltageSource(becauseofitstemperaturesensitiveNiMHbatteries),cannotoleratethesetemperaturesandshouldnotbeoperatedina slotnexttoaSIM954.

PrecisionSIMmodulesliketheSIM910andSIM911Preamplifiers, theSIM918PrecisionCurrentAmplifier,theSIM921ACResistance Bridge,theSIM922andSIM923TemperatureMonitormodulesand theSIM970QuadVoltmetermightshowincreasedtemperaturedrift whenoperatedclosetoaSIM954amplifierandwouldlikelybenefit frombeingthermallyisolatedfromaSIM954.

Aswithanyotherpoweramplifier,loadsshouldbeconnectedanddisconnectedwiththeamplifierpowereddowntoensuresafeoperatingconditions fortheSIM954andtheload.

Loadsshouldbecheckedfortheirabilitytohandlethevoltage,currentandpoweroutputlimitsoftheSIM954.

ManyBNCstyle50Ωloads,terminatorsandattenuators,powersplitters,mixers,etc.,areatriskofbeingdamagedbyaSIM954ifnofurther precautionsagainstoverloadaretaken.

1.3OperationUsinganExternalPowerSupply

UnlikeotherSIMmodules,theSIM954hasadditionalpowersupply filteringandprotectionagainstinversepolarityconditionsandis thereforsomewhatmoreforgivingwhenusedwithcustompower supplies.Awellregulated,lownoise,bipolarpowersourcewith ±15V,±1AoutputcurrentcanbeusedtopoweraSIM954module.

Aswithanyproductthatreliesonexternalpower,theuserisresponsibleto ensure that the supply never exceeds the maximum operating voltage, that shortcircuitcurrentsarelimited,andthatthermaloverloadisavoided.

AnySIM954usedoutsideofamainframeshouldbekeptinawell controlled thermal environment where none of the ventilation slots are covered and the sides are at least one inch away from any other surface.

In this manualitis assumed that the SIM954 is used inside a SIM900 Mainframe. Thespecifications of the module always refer to use inside a SIM900 mainframe.

1.4 Interfaces

ThereareatotaloffourBNCsontheSIM954frontpanel.Theupper twoaretheinputandoutputofChannel1,andthelowertwoarethe inputandoutputofChannel2.Thefrontpanelcallsouttheinput impedanceof50Ω,theoutputimpedanceof3.3Ωandthenominal gainof-4(12dB)intoa50Ωterminatedload.

Eachchannelhasanoverloadindicator, andthereisasingle"On" LEDonthefrontpaneltoindicate that operating voltage is applied to themodule. This is useful when the module is used outside of the SIM900 mainframe. The "On" LED does not indicate, however, that the powersupply voltage is correct and the powersource has sufficient output current top power the module under all load conditions.

1.4.1 SIMInterfaceConnector

TheDB-15SIMinterfaceconnectorcarriesallthepowerandcommunicationslinestotheinstrument.Theconnectorsignalsarespecified inTable1.1.

ThereisnomicrocontrollerinsidetheSIM954andthemoduledoes notcommunicateoveritsserialport.However,thestatus/servicere-questline(-STATUS)servesasanindicatorforanoverloadcondition whichcanbedetectedbythemainframeortheuser.Thissignalwill bepulledtogroundduringanoverloadcondition.Thedurationof thepull-downstateisapproximatelythesameastheon-timeofthe front-paneloverloadLED(approximately0.5s).

AllotherRS-232signalsareunused.

1.4.2 DirectInterfacing

TheSIM954isintendedforoperationintheSIM900Mainframe, but usersmaywishtodirectlyinterfacethemoduletotheirownsystems withouttheuseofthemainframe.

ThematingconnectorneededisastandardDB-15receptacle,suchas Tycopart#747909-2(orequivalent).Clean,well-regulatedsupply voltages of -15 and +15VDC must be provided, following the pin-out specifiedinTable1.1.Ground mustbeprovidedonpins1and8,with chassisgroundonpin9.The-STATUSsignalmaybemonitoredon pin2foralow-goingTTL-compatibleoutputindicatinganoverload condition.

The SIM954 has internal protection against reverse polarity, but there is no overvoltage protection on these powersupply pins.

PinSignalSrc⇒DestDescription		Direction
1	SIGNALGNDMF⇒SIMGroundreferenceforsignal
2	-STATUS	SIM ⇒ MF	Status/service request (GND = asserted, +5 V= idle)(Overloadconditionindicator)
3	RTS	MF ⇒ SIM	HW Handshake (+5 V= talk; GND = stop)(No connectioninSIM954)
4	CTS	SIM ⇒ MF	HW Handshake (+5 V= talk; GND = stop)(No connectioninSIM954)
5	-REF_10MHZ	MF ⇒ SIM	10 MHz reference (No connection in SIM954)
6	-5 V	MF ⇒ SIM	Power supply (No connection in SIM954)
7-15V		MF⇒SIMPowersupply
8PSRTN		MF⇒SIMPowersupplyreturn
9CHASSISGND		Chassisground
10	TXD	MF ⇒ SIM	Async data (start bit = “0”= +5 V; “1”= GND) (No connectioninSIM954)
11	RXD	SIM ⇒ MF	Async data (start bit = “0”= +5 V; “1”= GND) (No connectioninSIM954)
12	+REF_10MHz	MF ⇒ SIM	10 MHz reference (No connection in SIM954)
13	+5 V	MF ⇒ SIM	Power supply (No connection in SIM954)
14+15V		MF⇒SIMPowersupply
15	+24 V	MF ⇒ SIM	Power supply (No connection in SIM954))

Table1.1: SIMInterfaceConnectorPinAssignments, DB-15

The power supply must be able to provide both supply voltages simultaneously at 1 A load without significant dropout.

Failure to comply with these requirements may lead to malfunction and possibly destruction or lasting deterioration of the module's performance.

TheSIM954maypresentasignificantreversecurrentintothepower supplywhenturnedofforwhensubjectedtofaultyloadconditions.

Other loads on the same power supply can be put at risk by this behavior, and if necessary, additional isolation and protection in the form of reverse diodes, zener overvoltage protection diodes, and voltageregulatorshastobeestablished.

The SIM954 poweris internally well filtered, but it is recommended to use an otherset of RF beads and ceramic filter capacitors directly on the DB-15 receptacle in noisesensitive environments.

This is a standard measure for all RF amplifiers and is especially important with an RF module like the SIM954 which can deliver up to1Aofoutputcurrent.

2Generalproperties

InThisChapter

In this chapter general properties of the SIM954 are being discussed.

2.1DCCharacteristics....2-2

2.1.1DCGain....2-2

2.1.2 GainError....2-2

2.1.3 Offset Voltage and Input Offset Current ..... 2-2

2.2ACCharacteristics ......2-4

2.2.1 InputCharacteristics....2-4

2.2.2ACGain....2-5

2.3Noise....2-8

2.4Crosstalk....2-9

2.5Isolation....2-10

2.6PowerSupplyandThermalConsiderations.....2-12

2.1 DCCharacteristics

Unlikemostmediumandhighfrequencyamplifiers,theSIM954 doesnotcompromiseDCandlowfrequencypropertiestoachieve itsperformanceathighfrequencies.Itbehavesverymuchlikean idealamplifierwithfiniteoutputresistanceforawiderangeofloads andoperatingconditions.

2.1.1DCGain

TheDCgainofeachSIM954channelis-4or(12dB)into50Ω. This gainisloaddependent.Sincetheamplifierhasanoutputresistance of 3.3 Ω, the following formula describes the effective gain for a given resistiveload:

$$ G a i n (R _ {l o a d}) = - 4. 2 6 4 \times \frac {R _ {l o a d}}{R _ {l o a d} + 3 . 3 \Omega} \tag {2.1} $$

Inparticular, an unterminated SIM954 will have a DC gain of -4.264 (12.6dB), which is 6.6% higher than the nominal terminated gain.

If the SIM954 is used to drive a 75 Ω system, the expected DC gain is Gain (75 Ω) = -4.084 (12.2 dB).

2.1.2 GainError

ThetypicalgainerrorofaSIM954channelisapproximately1%, and theworstcaseerrorcanbeupto±3%. Withexceptionofafew applications, eventhoworstcasegainerrorisoflittleconsequence.

GainerrorsneedtobeconsideredwhentwoormoreSIM954channelsareconnectedinparallel. Thetwoamplifierscandifferbyupto 6%intheirabsoluteDCgain, and for10Voutputamplitudethisis equivalenttoa0.6Voutputvoltagedifference.

Sincethisvoltagedifferenceappearsacrosthettwo3.3Ωoutput resistors, a current of up to 0.6 V/6.6 Ω ≈ 90 mA can flow between thetwoamplifieroutputsreducingthestaticSIM954currentlimitof 500mAbyapproximately18%.

Themajorityofamplifierswillhavelowergainerrorsandthestandarddeviationforthecrosscurrentisonly30mAundermentioned circumstances.

2.1.3OffsetVoltageandInputOffsetCurrent

With a factory calibrated input offset voltage of less than 1 mV and an input offset current of less than 10 A , a DC precision of better than 2 mV (input referenced) can be achieved in 50 Ω systems.

Userswhowishtore-calibratetheinputoffsetvoltageandtheinput offsetcurrentcanusetheproceduredescribedinChapter4. DependingonthetemperaturerangetheSIM954isexposedto,this proceduremayslightlyimprovetheinputoffsetvoltage.

2.2ACCharacteristics

2.2.1 InputCharacteristics

TheSIM954hasoutstandingACinputcharacteristicsuptoabout 100MHzwithinputVSWRnotexcedding1.2:1.Between100MHz and300MHz,theamplifier'sinputimpedancefallstoaminimum of30ΩandaworstcaseVSWRof1.6:1.Attheworstfrequency, whichisjustslightlyabovethe-3dBpoint,theinputhasa0.25reflectioncoefficientor-12dBreturnloss.Sincethenon-idealinput

Figure 2.1: Typical SM1954 input preference

impedance will reflect part of the incoming signal energy at high frequencies, its necessary to either terminate the source output or keep the cable to the SIM954 input short. Tomaintain the best possible pulseresponse at 300 MHz ( _RG58 = 0.67m = 26'' ) the maximal cable length is 8.3 cm or 3.3", which is a 1/8 cable.

Short cables are especially important when two or more SIM954 channelsarebeingconnectedinseriesbecausethedrivingSIM954 channelisnotterminated. WhiletwoSIM954'sconnectedinseries bya4"cablewillstillhaveanacceptablepulseresponse,thesame combinationusedwith12"cableswillexhibitsignificantringingdue tocablereflections.

Figure22:Typical81M9546pupMSWSWR

If optimal response at the bandofanelectricallylongcabledrivenby anonidealsourceisofimportance,aninputattenuatorcanbeused tooptimizetheamplifier'sinputimpedanceneartheupperendof itsfrequencyrange.Bytradinggainflatnessagainstabsolutegain, satisfactoryresultscanusuallybeachievedevenwithelectrically longcables.

2.2.2ACGain

ThetypicalACgainisveryflatuptoabout10MHzandwillexhibit variationsof±0.2dBupto100MHz.Beyond100MHzthegainwill slightlypeak(<1dBor12%inamplitude).Beyondthepeakitwill falloffandreachits-3dBpointatabout300MHz.

Thesegainvariationsdependontheinternalcompensationofthe op-amps(whichareproductionlotdependent)andthetolerancesof thegainsettingresistorsintheSIM954.SincetheTHS3091op-amps usedinthismodulearetransimpedancetypes,thegainpeakingand the-3dBpointarecontrolledbythefeedbackresistor.

ThecurvesshownarebasedonarandomlychosenSIM954prototype andarecharacteristicfortheproduct. However,SRSdoesnottest fortheworstgainvariationwithaprecisionthatresemblestheplots

shown. Thegainvariationguaranteedbydesignandourcalibration procedureassurethatthegainwillstaywithin±1dBoftheideal. If amorepreciseknowledgeofthegainandphaseoversomepartor allofthefrequencyrangeisrequired, theusercanperformsucha measurementwithasuitablevectornetworkanalyzeronthemodule ofinterest. Thisisespeciallyimportantathighfrequencieswherethe inputandoutputimpedancewillinteractwiththedriverandload impedanceandcausereflectionsoncables. Allmeasurementsare takenbysuppressingtheinputmismatchwitha10dBattenuator directlyattheSIM954input.

Figure2.3:TypicalISM1954gagaploplot

Figure2.4 Typical SIM1954 phabaplot

2.3Noise

TheSIM954amplifierstagesarecompoundamplifiers. TheRFpower amplifiercontainsfourTHS9031current-feedbackoperationalamplifiersperchannel. Theseamplifiershave2nV/ typicalequivalent inputvoltageand14pA/ typicalcurrentnoise(Johnsonnoise above100kHz)each. Theparalleloperationeffectivelyhalvesthe inputvoltagenoiseanddoublesthecurrentnoise. Amplifiernoise accountsfor1nV/ and28pA/ inputnoise. Theresulting noisematchingresistanceof1nV/ /28pA/=36 isvery closetothesourceresistance, and the amplifiernoisecontribution is low.

Including the feedback resistors, this compound amplifier can be calculated to have a theoretical Johnson noise floor of 1.95 nV/ when driven with a 50 source.

Noisemeasurements onSIM954stageshaveyieldedJohnsonnoise databetween1.85nV/ and2.45nV/ . Thelowerfigurewas obtainedat100MHz,whilethelargernumbercoincideswithslightly higher noise at 160 MHz. The increase in noise (gain) at higher fre- quenciescanbeattributedtotheincreasing(capacitive)mismatchof theSIM954inputtothedrivingimpedanceandparasiticimpedances intheamplifier'sfeedback. Thechosencompensationoptimizesa combinationofgainflatness,bandwidth andstepresponseandsacr- rificesnoiseperformanceclosetothebandwithlimit.

TheSIM954's Johnsonnoise is better than 3nV/ for amplifiers driven by 50Ω sources.

Theresultingnoisefigurefortheidealamplifierisabout8dB,while theguaranteednoisefiguredoesnotexceed11dB.Actualproduction modelswillbesomewherein-between.

Because of its relatively low gain and medium noise figure, the SIM954doesnotqualifyasalownoiseamplifier, butitwillstill yield reasonable noise performance in applications which can tolerate its modest 11 dB noise figure while requiring only small gains at largeamplitudes, adomainwhichisusuallypoorlycoveredbyother amplifiers.

2.4 Crosstalk

ThetwochannelsofaSIM954modulearenotshieldedfromeach otherandexhibitcrosstalk.Becauseofthegeometricasymmetryof themodule,theoutputofChannel1isclosertotheinputofChannel2thanviceversa.Thecrosstalkwillgenerallybehigherfrom Channel1thanChannel2.Thisshouldbetakenintoaccountin applicationswhichrequiretheleastamountofinterferencebetween thetwochannels.Theworstcrosstalkiscausedbyaresonancein

Figure2.5SMM94Crosstalkk

the module's powerp plane in order to work with the operational amplifier's discriminishing common mode rejection at high frequency. Since the frequency of this resonance is at approximately 385MHz, itiswellabovetheamplifier's guaranteed band with limit. Under normal circumstances should be of little concern.

2.5Isolation

Because each SIM954 channel is an inverting current feedback amplifier, the input node is connected via an effective ≈ 50 resistor to the virtual ground node of the amplifier, which itself is connected to the output via an effective ≈ 220 feedback resistor.

Because the amplifier's transimpedance gain is finite, the isolation between the output and the input port is also finite. Asthe loop gain diminishes at higher frequencies, the output to input isolation will decrease, and larger fraction of the RF energy at the output will appear at the input of the amplifier.

Whilethisisgenerallyoflimitedconcern,itcanbecomeaproblem ifthisRFenergycanleakintohighgainorhighQ(qualityfactor) circuitsconnectedtotheamplifierinput.

Highimpedance, highQresonantcircuits (e.g. tanks, opentransmissionlines, crystalsetc.) can be excited, and oscillation of the amplifier and the frequency selective element can occur. Limited isolation properties are more likely to become a problem if the output is in correctly terminated as well, where the load reflects RF energy back into the amplifier. Sincethephaseshift between input and output changes at higher frequency, making the feedback more "positive," parasitic oscillations duetolimited isolation are most likely to occur near the amplifier's bandwidth limit.

When multiple amplifiers are connected in series to increase the gain, or used in parallel to increase output current or voltage in abridge circuit, the finite isolation and destabilizes amplifiers even in wide band, low Qcircuits. Again these oscillations are most likely going to occur at frequencies of the amplifier's band with limit (i.e., in the 100 MHz to 300 MHz range).

Ifoscillations(oranincreaseinnoisegain)areobserved, isolation between the amplifier and the driving potterminating circuit shasto be increased. This can be accomplished with attenuators (toreduce overall gain), isolating power splitters (to isolate multiple inputs) or by using frequency selective circuits likely low pass and bandpass filters (toreduce again at the highest frequencies at which isolation is worst).

The following diagram shows the measured disolation between a SIM954 output and its input. The measurement was made with a network analyzer by connecting the source to the amplifier's output and then the network analyzer input to the amplifier's input.

Boththeisolationinamplifier'on'andamplifier'off'configuration areshown.Withtheamplifierpoweredon,theisolationgetsincreas-

inglyworseathigherfrequencies,whilewiththeamplifieroffitgets increasinglybetter.Atthehighestfrquency(500MHz),wellabove theamplifier'sbandwidth,bothcurvesconvergetoroughlythesame value,whichisessentiallyameasureoftheparasiticimpedancesof theamplifier'sfeedbackpath.

Figure2.6:SIM954outputtoinputisolation. Thedashedlinerepresentspower-offisolation, the solidlinerepresents the powered state. The curves are interpolated between measured data (dots).

2.6 Power Supply and Thermal Considerations

ASIM954modulecaninitiallydrawupto750mAofpowersupply currentfromboth±15VrailsoftheSIM900mainframe.Itistherefore recommendedthatyoulimitthenumberofSIM954modulestofour permainframetostaywithinthe3Apowersupplylimits.

Iftwoormoremodulesareusedinonemainframe,theyshouldnot beplacedinadjacentslots,andSIM954sshouldnotbeplacednextto temperaturesensitivemodulesliketheSIM928orSIM965.ASIM954 candegradethetemperaturedriftofotherSIMmodules,andcare shouldbetakentoavoidsuchconfigurationsinapplicationsthatrely ontheprecisionoftheSIMsystem.

Theseamplifierscangeneratemoreheatbydesignthanasinglewide modulecanconducttothemainframe. In the worst case, a SIM954 candissipatecloseto25Wofpower. However, sincethe internal powersupplycircuithasanegativethermalfeedback, the module will quickly reduce the power consumption to 15W by limiting the supply current to about 500mA.

Themaincoolingmechanismofthemoduleisconductiveandthe heatwillflowtowardsthefrontpanelwhichwillgetnoticablywarm (upto50 °Cor130 °F)foramoduleoperatedina25 °Cenvironment. Higherenvironmentaltemperaturescanleadtothermalshutdown of theop-ampsandhighlydistortedsignalwaveformsinmodules whicharedriventotheirfullpowerlimits. Thethermalshutdown is reversible and will not lead to long termdamage of the operational amplifiers. However, the built–inelectrolytic decoupling capacitors will degrade if themodule's internal temperature is near or above 50°C for hundreds or thousands of hours.

Temperaturesonthefront-panelBNCsthatareuncomfortabletothe touchareagoodindicatorthatthemoduleisbeingusedaboveits long-termpowerhandlingcapability.

3Applicationnotes

In this chapter properties and limit so the amplifier and its performance in typical applications are discussed. In This Chapter

3.1 ResistiveLoads....3-2

3.2CapacitiveLoadHandling....3-3

3.2.1 CapacitiveReverseCurrents.....3-4

3.3 Inductive Loads....3-5

3.3.1 DCCurrentandInductorSaturation.....3-6

3.3.2 Inductive Voltage Spikes......3–7

3.4 Transformers....3-8

3.4.1 InputSideTransformer....3-8

3.4.2PowerSplitterandBridgeoperation.....3-8

3.4.3OutputSideTransformer....3-9

3.5LoadImpedanceMatchingExamples......3-10

3.6BridgeConfiguration....3-11

3.7TypicalApplication:aHighVoltageIsolated,Low Noise,DC-DCConverter ....3-12

3.7.1 CircuitDescription ......3-12

3.8CommonModeEMI/EMF....3-16

3.9OverdriveBehavior....3-18

3.10 MiscellaneousLoads....3-20

3.10.1 HeatersandPeltierElements .....3-20

3.10.2 Filaments....3–20

3.10.3 DrivingPowerMOSFETs .....3-20

3.10.4 PiezoElements .....3-21

3.10.5 ElectricMotors 3-21

3.1 ResistiveLoads

TheSIM954canoperateonresistiveloadsrangingfromshortsto openoutputs.

Because of the finite output resistance and current limit, the amplifier's gain and output voltages swing are load dependent. There are three important cases of load limiting:

• Forloadimpedancesbelowapproximately7.3Ω,theoutput voltageislimitedbythehighestoutputcurrentof1A.This limitistransient(i.e.,itcanonlybereachedforshortpulses beforetheinternalpowersupplycurrentlimiterreducesthe powersupplyvoltageonbothamplifiers).
• Thecontinuousaveragecurrentdrivinglimitis500mA from eachpowersupply.Sincethisisthesumoftheaveragesupply currentsofbothamplifiersononerail(i.e.,eitherpositiveor negative),itispossibletodriveanaveragecurrentof+500mA indefinitelyfromoneamplifierchanneland-500mAfrom the second,butnotthesamepolarityfrombothatthesametime. ThismeansthattheSIM954willdevelopitsfulloutputpower in differential and push-pull configurations. However, care has tobetakennottothermallyoverloadtheSIM954inthismode.
• Finally, loadresistances above 18Ω limit the output current below both the transient and continuous limits and can be driven for an arbitrarily longtime (assuming that the other channel does not overload the powers supply current limiter).

Thelastcaseimpliesthatfor50Ωloads,theSIM954candrive10V intotheloadontwochannels(at200 mAeach),andforhigherload impedancetheoutputvoltagecanriseashighas10.667V(foran openoutput)withoutoverdrivingthecircuit.

Figure3.1 show sthemaximal output voltage as a function of load resistance.

If the combined output current of both channel exceeds 500 mA to 700 mA, a floating one either powersupply rail, the built-in power supply current limiter will gradually reduce the powersupply voltage available to both amplifiers and the built-in buffer capacitors are discharging. This will be seen as a gradual decrease in output voltage and an increasing level of distortion (clipping). The amplifier should not be operated in this way if signal quality is of importance.

Figure 3311SIM954 output voltage regulator function load resistance

3.2 Capacitive load handling

Because the activity protocol of each 3M95405-4-phenylphthalanohisisolated from the holiday by 3C series resistor, capacitive loadswill limit the amplifier's bandwidth by forming an RC-low pass filter. The advantage of adding an output resist to the actual amplifier is that it will remain stable for all possible passiveloads. However, the series resistance will also limit the amplifier's bandwidth when driving capacitive loads.

A100pFcapacitor, which is roughly equal to 1m(3') of unterminated RG58 coaxial cable, will form an RC-lowpass filter with 330 ps time constant and 480MHz corner frequency. Above the RC corner frequency, the AC voltage on the capacitive load will fall off with an additional 6 dB/octave, but the amplifier will still be able to drive up to 1A peak AC current into the load.

Capacitiveloadslargerthan100pFwillseverelylimitthebandwidth, andinadditionwillalsoreducetheslewrateforlargescalesignals because the amplifier's output current is limited. The SIM954's1A current limit leadsto an impressive 1000V/ slewrate for 1nFcapacitiveloads.

Whendrivingfastrisetimepulsesintosmallcapacitiveloads,cable inductancecanleadtoresonantpeaking,asshowninfigure3.2.If flatfrequencyresponsebelowtheRC-cornerfrequencyisimportant, cablelengthsandimpedanceshavetobecarefullymatchedtothe application.Forlargercapacitorsandelectricallyshortconnections, theseeffectsarenotimportant,andthewaveformsaresimilarto thoseofapureRClowpassfilterasseeninfigure3.3.

Figure3.2: The SIM954 driving a 1nFceramic capacitor with a 2MHz square wave to 20Vpp

Figure3.3: The SIM954 driving a 100nFceramic capacitor with 100kHz square wave to 20Vpp

3.2.1 CapacitiveReverseCurrents

Everycapacitorstoresachargeequivalenttotheproductoftheap- pliedvoltageanditscapacitance.Thischargecancauseareverse currentflowiftheamplifieristurnedoffwhileitremainsconnected toachargedcapacitor.SincetheSIM954doesnotguaranteebyde signthatthisreversecurrentwon'tharmtheamplifierortheSIM900 mainframe,cautionshouldbeusedwithcircuitswhichdrivelarge capacitiveloadsorevenelectrochemicalcellslikebatterieswhichcan storeverylargeamountsofcharge.

If a large reverse current ( ≥ 10 mA for 1 s) may flow into an un-poweredSIM954theusershouldconsideraddingarelayscontact betweenhemodule'soutputandtheload. Therelayscoilcanbe powered by the mainframe's ± 5, ± 15 or +24 V or the user supplied voltagetoclosethecircuitonlywhentheSIM954isunderpower.

3.3InductiveLoads

Similartothecaseofcapacitiveloads,inductiveloadsandtheamplifier'sfiniteoutputimpedanceformseriesRLcircuits.Sucha circuitbehaveslikeahighpassfilterwitha3dBcornerfrequencyof f = R / 2 L .

A1μHinductorwillforma525kHzhighpassfilterwiththe3.3Ω outputresistor.Often,theamplifierwillbeusedtodriveinductors abovethiscornerfrequenciy,butthisisnotalwaysthecase.

In Figure 3.4 the amplifier was driving a 1 H inductor with a 1 MHz squarewavewith750mA pp.ThecleanRL-highpassresponsecanbe easilyseen.Whilethevoltageontheinductorgoestoalmost0V,the amplifierisstilldrivingthefullcurrent.Thehighestoutputvoltage inthiscasewaschosensuchthattheamplifierdoesnotreachits1A current limit,and stays in its linear regime.Had a larger driving voltage been applied,the nonlinearity due to the saturation of the outputcurrentwouldhavebeenvisible.

Most importantly, since in this case the internal power dissipation is proportional to the output current times the amplifier's power supplyvoltage, evena500mAaveragecurrentwillleadtonoless than 7.5 W of additional power dissipation. If such RL highpass filterbehaviorisobservedathighsignallevels, asignificantamount of heat will be generated in the amplifier. Users need to carefully evaluateethermalloadandtheresultingheatingoftheSIM954and mainframe when driving inductive loads below their RL-highpass cornerfrequency.

Figure3.4:TheSIM954drivinga1MHzsquarewavewith750mA peakcurrentintoa1μHinductor

3.3.1DCCurrentandInductorSaturation

SinceinductorsareessentiallyDCshorts,drivingevenasmallDC voltageonaninductorwillleadtolargeDCcurrents.Itisimportant toverifythattheamplifier'scurrentandthermalpowerdissipation limitsarenotviolatedbysuchacondition,andthattheinductor isactuallyabletohandletheoutputcurrent.Coresaturationin inductorswoundonironorferritecoresshouldbeavoidedbecause oftherapidriseinlossesforACcurrentsinthesaturatedcore.

Figures3.5and3.6showanexampleofinductorsaturation.The SIM954isdrivinganultra-highpermeabilitycorewithalmostrect- angularmagnetizationcurve,usedinafluxgatemagnetometer,with a10kHzsinewave. Thecoresaturatesshortlyafterthevoltageon thecoilpassestheextremalvalues. Becauseoftherapidlossofthe core'sabilitytostoreanyfurthermagneticenergy,thevoltageon thecoilbreaksdown,whileatthesametimethecurrentincreases rapidly.

Figure3.5: Voltageonfluxgatemagnetometercoildrivenwith10kHzsinewave

Figure3.6: Currentthroughfluxgatemagnetometerdrivenwith10kHzsinewave

Sincethevoltageattheoutputofthemodulegoestozeroatthe sametimetheoutputcurrentrises, asaturatedinductorpresents averyheavyloadtotheamplifier. Ingeneralitisbetterteroavoid saturatinginductors. However, if the SIM954 is used to deliberately drive inductorsintosaturation, as in the example of the fluxgate magnetometercoil, careshouldbetakentoavoid the amplifier's current and thermallimits.

3.3.2 Inductive Voltage Spikes

Every(non-saturated)inductorstoresanamountofenergyequal to E = I^-2L / 2 in its magnetic field when it is excited by a current I . If the current loop is suddenly opened (e.g. by opening the circuit between the current source and the inductor), this energy will lead to arapid buildup of voltage across the inductorduetoselfinduction and Lenz's rule. This inductive voltages spike can exceed these safe operating limit so the amplifier's ±15V powersupply rails and lead to destruction of the amplifier.

Inductiveloadsshouldonlybepluggedinorremovedfromtheamplifier whilethepowersupplyisturnedoff.

If the amplifier is being used as a coil driver, as suitable external voltage protection device (power zener diode, transient voltages suppressor, etc.) should be used.

3.4 Transformers

Transformersareinductiveloadswhichareofgreatimportancein practicalapplications.TheSIM954hasexcellentpropertiesintransformercircuits.

Transformerscanbeconnectedtoboththeinputandtheoutputofthe SIM954, andinmanyapplicationssuchatopologyisadvantageous.

3.4.1 InputSideTransformer

AninputtransformertotheSIM954can, butdoesnothavetobe isolated. Autotransformersandwideband transmissionlinetransformersareequallywellsuitedtodrivethemodule.

Aninputsidetransformerwithoutaseriescapacitorwillpresenta DCshorttotheSIM954.Becauseofthesmallinputoffsetcurrent, theadditionalDCerrorwillbelessthan1mVandisacceptablefor mostapplications.Thiscircuithastheadvantagethatitguarantees thattheoutputisDCfree,whichisimportantifthemodulehasto alsodriveanoutputtransformer.

The transformer's inductance will form an LChighpass filter with the 50 input impedance of the module. For an RF transformer with 1 H secondary winding inductance, the -3dB corner frequency will beat 7.96MHz.

It follows that a practical input transformer that covers a lower corner frequency f should have a secondary winding inductance of at least 8 H × . The primary inductance will then be determined by the square of the winding ratios.

3.4.2 PowerSplitterandBridgeoperation

Aninputtransfomerisoftenusedasa180 ° powersplittercircuit. The two outputs of such a splitter can drive the two SIM954 amplifiers in onemoduledifferentially and180 ° outofphase.

Thetwoamplifierswillactasadifferentialdriverwhichhastwice theoutputpowerofasinglechannel.

A180 ° splitterasshowninfigure3.7usesatransformerwitha singleprimaryandasplitsecondarywindingwithawindingratio of 2:1 . At this ratio it matches both input and output impedances to 50Ω. However, the naive transformer circuit omitting R1 would notisolatethetwooutputportsfromeachother,whichcanleadto crosstalkandunwantedfeedback.Wilkinson ^1 proposedtheshown

180 Degree Power Splitter V1 50 SINE(0 1 1e6) 100μH L2 49μH L1 L3 49μH R1 24.5 SIM954 R2 50 SIM954 R3 50

Figure3.7:180 ° powersplittercircuit

circuittopologywhichaddsisolationbetweenthetwooutputports withoutsacrificinganysignalpower.

Intheproperlyterminatedbalancedcircuitthecentertapnodeis avirtualground,andnocurrentwillflowthroughresistorR1.If powerisreflectedintothetransformerbytheloadoneitherofthe splitteroutputs(i.e.,inthiscasetheSIM954inputs),someofitwill betransferredtothisloadresistorandwillnotbevisibleattheother outputport(althoughsomepowerwillstillmakeittotheinputport because the circuit does not have perfect isolation between all ports).

ItshouldbenotedthattheSIM954requiresanisolatedpowersplitter indifferentialdriverapplications.Highfrequencyoscillationshavebeen observedwithsomenon-isolatedsplitters.

Itisconvenienttoapproximatethenecessary 2 turnratioswith multiplesof7:5or10:7turnratios. Theresultingmatching errorsaresmallandcanusuallybeneglected. Andwhiletheydo resultinanon-idealisolationcharacteristicsofthecircuit, thiscan (atleasttheoretically) bereducedbyloweringtheresistanceofthe internal isolation resistor from 25 to 24.5 . However, in a typical implementation the difference is likely going to be lost in errors caused bycomponenttolerancesandstrayimpedances.

Thesephasesplittersarecommerciallyavailablefrommanysources (e.g., Mini-Circuits), but suitable transformers can also be easily madefromtoroidalRFcores.

3.4.3 OutputSideTransformer

ThemoreinterestingandchallengingcaseisoperatingtheSIM954 withanoutputtransformer.CaremustbetakenthatnoDCcomponentsarepresentonthecircuit'soutputwhendrivingatransfomer directly.ThiscaneitherbeachievedwithaDCblocklikeaseries capacitor,orbymeansofaninputtransformer.

BlockingDCcurrentsprotectsboththeamplifieraswellasRFtransformerswhichcanbedamagedbytheamplifier's1Aoutputcurrentcapability(especiallywidebandRFtransformerswhichareoften woundwithverythinwiresonsmallcores).

While series capacitors may also be used as DC blockson the output, care must be taken that they donot form high Q series resonance circuits with the transformer's winding inductance. The better way to avoid DC voltagesisto connect both amplifier inputs and outputs directly to transformers. This adds the least number of polesto the circuit's transfer function and will lead to abenign and well defined frequency response.

Inthiscase, the low DC input offset voltage will lead to an output offset of nomorethan 5 mV to 10 mV, and the built-in 3.3 Ω output resistance will limit DC output current to a few milliamps—avalue which all but these smallest RF transformers can handle safely and without signal degradation.

Themainadvantageoftransformercouplingistheaddedpossibility ofloadimpedancematchingandbridgeoperationwhichallow the useoftheSIM954asasmallRFpoweramplifier.

3.5 LoadImpedanceMatchingExamples

TheSIM954isdesignedtogenerateupto1Aoutputcurrentinto low impedances and up to 10 V output voltage into 50 Ω. Because ofitslowoutputimpedanceof3.3Ω,however,theamplifiercannot fullydriveintoa50Ωloaddirectly,whichwouldlimitthecurrentto approximately 10V50 = 200mA ,afactoroffiveshyoftheamplifier's outputcurrentlimit.

The actual amplifier(without series resistors) will be able to generate 10.6 V before the overload detection circuit indicates an invalid operating state. Themost power is available at the output when the actual amplifier produces its highest output voltage and A output currents simultaneously.

This is equivalent to power matched load resistance of 10.6Ω. By subtracting the internal series resistance of 3.3Ω from this ideal load, we arrive at an ideal external load of 7.3Ω. The most power that can be extracted from a single SIM954 channel using a 7.3Ω load is then 7.3W _peak .

Tomatchtheidealloadtoa50Ωsystem,anoutputtransformerwith avoltageratioof 50/7.3 ≈ 2.62 is required. The closest ratios that canbeasilyachieved with widebandRFtransformers which can onlyhaveafewturnsoneitherprimaryandsecondarysideare:

• 2.5with5:2turns,
  -2.6with8:3turns,
  •2.75with11:4turnsand
• 2.4with12:5turns.

The8:3turntransformerwillleadtoa7.03Ωloadimpedanceas seenbytheamplifier(i.e.,a1Aoutputcurrentlimittranslatesinto 7W peak and4.9W eff forsinewaves).

3.6BridgeConfiguration

Byusingbothaninputandanoutputtransformer,twoSIM954channelscanbeoperatedinabridgeconfiguration,therebydoublingthe theoreticaloutputpowerto14W peak andcloseto10W eff .Thenecessaryoutputimpedancetransformationrequiresa 50 / 14.6≈ 1.85 ratio.Thisisbestachievedwitha9:5turnratioforafactorof1.8.

Asinthecaseoftheinputsplitter, anisolatedpowercombinershould beused (althoughisolationisnotasimportantasontheinputside).

3.7 Typical Application: a High Voltage Isolated, Low Noise, DC-DC Converter

Theability of the SIM954 to drives significant power into a transformer can be used to provide isolated powertocircuits under unusual circumstances for which no easy commercial solutions exist. In the following wedescribea ± 5V, 100mA isolated DC-DC converter with 20k Visolation. Remarkably, the circuit exhibits less than 50μV output ripple and noise.

3.7.1 CircuitDescription

In order to achieve 20 kV isolation voltage with minimal effort, Dearborn 392250 20kVDC, 150 °C UL 3239 Style high voltage wire is used to build a 1:1 isolation transformer Fair-Rite 2843009902 dual-aperture core. This large broadband noises suppression core has two 0.250" holes which can accept twoturn so the Dearborn high voltage wire. A singeloop of wire is used for the primary and a second, isolated loop for the secondary winding. The windings have enough inductance to operate this transformer between 250 kHz and 1 MHz. Toward the lower end of this range, this transformer is limited by its low winding inductance, and above 1 MHz the core losses in the Type 43 material of this core will dominate and limit performance. Other core materials and larger cores, which allow for higher inductance, can extend the frequency range of this design considerably.

The primary winding can be driven directly by the SIM954 through a 50 Ω coaxial cable. The cable lengths should not exceed 3' to avoid losses due to mismatched termination. Since neither the SIM954 nor the transformer load are matched to the 50 Ω cable impedance, the coax will have a complex impedance.

+6V, 100mA, 100uV ripple, 20kV Isolation voltage DC/DC converter with SIM954 sinusoidal driver. SIM954 3" RG58 Td=5n Z0=50 T1 100nH beads on HV cable close to core L1 L2 C1 1nF D1 1N4148 600Ohm/100MHz 1206 SMT beads L3 C3 10μF C5-C8 Ceramic Chip L5 10μH L7 10μH C7 10μF C9 100μ R1 56 SINE(0 6 500kHz) Rser=50 20kV isolation transformer one turn each of Dearborn 392250 on Fair-Rite 2843009902 core. C4 10μF C6 10μF C8 10μF C10 100μ Simulated Load 3 turns on Fair-Rite 6611 TYPE 43 multi aperture bead All physical construction on PCB with ground plane using RF design rules. All current loops have to be minimized, wires should be twisted where possib Magnetic shielding of the core may increase performance.

Figure3.8: Schematicofthe20kVisolation, sinusoidaldriveultra-lowrippleDC-DC converter.

Acablethatisphysicallyveryshortcomparedtothewavelength

of the driversignal(200mfor1MHzon50Ωcoax)will typically perform best without impedancematching LC-circuits at one or both ends.

Thetransformer'ssecondarywindingisconnectedtoasimplehalf-waverectifiermadefromfastswitchingdiodessuchasthe1N4148.

Inordertoachieveminimumswitchingnoise,theSIM954isused todrivethecircuitwithasinusoidalvoltageratherthanasquare wave(asinordinaryswitchingpowersupplycircuits).Thisensures thattherearenospectralcomponentsbesidethemainoperating frequencypresentattheoutputofthedriver.Afterthetransformer, theswitchingoftherectifierdiodesproducessignificantswitching transientswhichhavetobefiltered.1nFcapacitorsinparallelwith thetwodiodesslowdiodeturnonandturnofftimesdown.Slower transientssignificantlyreducenoiseincomparisontoconventional convertercircuitswhereultrafastdiodesareusedtoachivehighest possibleconverterefficiency.

Therectifiedcurrentisfilteredbyapairof10μFceramiccapacitors followedbytwosetsofbeadsandceramicandTantalumcapacitors. Inthiscircuit, six-aperturethroughholebeads (Fair-Rite6611 type 43) were used, but highimpedancemulti-layersurfacemountbeads are preferable in applications which are very noisesensitive and have to improve the performance of this demonstration circuit. In general, the lowest ESR (Equivalent Series Resistance) capacitor shavetobe used. Multiple ceramic capacitors in parallel are much better than asingle capacitor with the same equivalent capacitance because the parallel circuit reduces lead inductance and ESR. More capacitance to suppress the fundamental frequency can be added using high quality tantalum or organic electrolyte capacitors.

MultipleconsecutiveLCfilterstagesshouldbeusedforoptimum results,withthefirststagesusingRFbeadstosuppressthehigh-estfrequencycomponentsfirstbeforerejectingthefundamentalfrequencyandlowerharmonicsinthelaterstages. ProperRFdesign techniquesandagroundplaneareabsolutelynecessarytoachieve theshownresults.

Theresidualswitchingnoiseofthisdesignweremainlydependent onwiringgeometryandthesizeofthecurrentloopoutsideofthe core.Iflowestpossibleswitchingnoiseiscritical,themagneticfields from thecoreandthecurrentloopshavetobeshieldedwithsuitable RFshields.Useoftightlytwistedwirestoreducemagneticcoupling isvital. TracescarryingACcurrentsshouldbekeptshortandbe routedaboveagroundplaneorsandwichedbetweenwoground planesoninnerlayers.

Ifvoltageregulationisnecessary,low-drop-outvoltageregulators

canbeusedtostabilizethe±6Vfilteredvoltagetoloadindependent ±5V.

The following output tripple measurements in figures 3.9 and 3.10 illustrate the enormous advantages of sinusoidal drive DC-DC converters.

Figure3.9: Noise measurement for 500kHz square wave drive producing an output voltage of ±6V at 100mA load. At 10mV per division vertical oscilloscope gain the effective scale is 400 μV per division. Every edge on the driving voltage causes target transients with a peak amplitude of 1.67mV peak and an RMS amplitude of 88μV rms.

AllmeasurementsweretakenwithaSIM914dual350MHzpreamp withbothchannelsinseries,givinganequivalentgainofx25in additiontotheoscilloscope'sverticalgain.

Mostofthespectralenergyintherippleofthesinusoidaldrive converterisinthefundamentalandsecondharmonicfrequency. Bothcomponentscanbefurtherreducedbycarefullycontrolling thecurrentloopsinthecircuitandarebynomeansoptimal. The circuitatthispointwassosensitivetowiringgeometrythatno furtherreductionwasattemptedsincetheultimateperformancewill depend on the particular application of this converter. However, one canestimatefromtheresultthatpeak-peakrippleof50μV pp and RMSnoiseontheorderoflessthan10μV rms isarealisticdesigngoal.

Forimprovedcommonmoderejection, the transformers should be

Figure3.10: The SIM954 driving the same circuit under identical load conditions with sinusoidal voltage. Thesharptransients are almost gone. Plesenotethat the oscilloscope is now set to 1 mV per division, i.e. the effectivescale is now 40 μV per division. The peak-to-peak amplitude is 87 μV pp and theripple RMS is 17 μV rms.

drivendifferentiallywithtwoSIM954channelsbyusinganisolating 180° powersplitterontheirinputstomakeaclosetoidealsinusoidal differentialdriver.

3.8CommonModeEMI/EMF

All(coaxial)cableshavetwomodesofwavepropagation. Thedifferentialmodeischaracterizedbythevoltagedifferencebeingexclusivelybetweenthetwoconductors. In the case of coax, this means the electric and magnetic fields are contained between the inner conductor and the shield. The current on the inner conductor is exactly oppositeto the current on the shield. In this mode, coaxial cables are perfectly shielded and donotact asantennas.

Commonmodesignals, however, are characterized by the inner conductor and the shield being at the same potential, and current on both flowing in the same direction. In this case, there will be substantial inductive potential drop along the cable which will, ineffect, act like a wire antenna of equal dimensions.

Inpractice, commonmodeexcitation of cables softengoes unrecognized because on a properly terminated, ideal, lossless cable the commonmodewill never be excited. Most theoretic explanations about the function of coaxial cables only taken differential modesignals into account and fault mention them more problematic case of commonmodeexcitation. However, cable losses and improper termination one either the transmitter or receiver end will commonly lead to modemixing, and some of the signal energy from the desired differential mode will leak and appear as a common mode signal (i.e., radiate an electromagnetic signal to freespace from the shield of the cable).

Inpractice, the EMI (electromagnetic interference) emitted by typical RG58BNC cable wiring can often lead to a noticeable feed though, crosstalk, feedback and even oscillations in RF systems with a total signal gain of 60 dBormore.

SincetheSIM954isanamplifierwithverylowoutputimpedance, amplifieroutputsideterminationispoorbydesign.Inaddition,the signalgainandthehighpoweroftheamplifierincreasethelikelihood of problematic EMI levels. This is compounded by the fact that theproductisspecificallydesignedtodrivenon-resistive,andill-terminatedloads.Inmanycasestheloadwillalsobeinsufficiently shielded (e.g., magnetic coils) and present unwanted but efficient antennacharacteristics.

Tocontrol the possibly severe effect of common mode excitation, we suggest that clip-oncable beads (likethe Steward part number 28A0392-0A2orsimilar) should be used directly at the output of the amplifier and nearill-terminated (i.e., reflective) loads.

Thesebeadsareeasytoinstallandcanpreventa hostof common mode EMI problems generated by the fast and powerful SIM954

amplifierstage,especiallyinthefrequencyrangeabove10MHz. Anycommonmodesignalwillbeattenuatedbythebeadwhichacts likealossyinductorandincreasesthecommonmodeimpedanceof thecable.

Whilethesebeadsaremosteffectiveforhigherfrequencies,theirfrequencyrangecanbeextendedbyrunningthecablemultipletimesthrougha(largerdiameter)specimen.Thisincreasestheinductanceatlowfrequenciesbythenumberofturnssquare(i.e.,three turnswillincreasetheinductancenine-fold).BeadmaterialsusuallyhaveverygoodRFpropertiesfarbelowthefrequencyoftheir highestattenuationandmakeexcellentcommonmodechokes.The increaseoftheinductancetogetherwiththedecreaseofdampingat lowerfrequenciescanmakemulti-turnbeadsresonantwithuseful Q-factorsofapproximately2to50.Acommonexploitofthisparallel (andthereforhighimpedance)self-resonanceistouseittosuppressnarrow-bandnoise.Itisimportanttorecognize,however,that thebeadimpedancewillturncapacitiveabovetheresonancepoint, whichcanleadtounwantedresonancewiththecableinductance.

Beads will have no noticeable effect on differential mode signals which have current that cancel out on the inner conductor and the shield, and therefore generate tenomagnetic field outside of the cable.

Sincethesebeadshavetobeinstalledoutsideofthemodule'sFara-dayshieldandareapplicationspecific(attenuationatthesignal frequencyofinterestdependsonthesizeandmaterialofthebead), theycannotbeincludedintothedesignoftheamplifier. Itisthe user's responsibility to be aware of these effects and filter properly.

Anexampleofa typicalcommonmodescenario isshowninFigure3.11whereaSIM954isdrivinga4 V _pp ,10 MHzsquarewaveinto an8"longstubantenna.Thiswouldbethylicalofdrivingarelativelysmallunshieldedcoilorsimilarload. Thevoltagebetween theSIM900mainframechassisgroundandtheSIM954outputBNC groundwasmeasuredwithan oscilloscopewith300 MHzbandwidth withandwithouta275Ω(at100 MHz)clamponbead.Thesame beaded cable (as shown in fig.3.12) radiates significantly less and also reducestheamountofconductedRFonthemainframeground.

Clip on beads are a simple solution to comply with EMI/EMF requirementsbutdonotguaranteethattheradiatedemissionsofthe modulearewithinanyspecificcompliancelimits.Doubleshielding andcontrolofthefrequencyspectrumofthedrivingsignalmight alsobenecessary.

Figure3.11: Commonmode voltage at the amplifier output ground relative to SIM900 mainframe chassis which driving an 8 inch longstubantennawitha4V _pp square wave at 10 MHz.

Figure3.12:Sameconditionsbutwitha 275Ω(at100MHz)clamponcablebead. Thepeakamplitdehasbeenreducedbyapproximately6dBandtheringingissubstantiallyshorter.

3.9OverdriveBehavior

Theamplifierexhibitsdifferentkindsofoverdrivebehaviordependingonloadandfrequency. Themostbasicoverdriveconditionisa voltageoverdriveonlightloadasshowninFigures3.13and3.14.

Figure3.13:TheSIM954drivenwith1kHz trianglewaveto20Vppinto50Ω

Figure3.14: TheSIM954overdrivenwith 1kHz trianglewaveto>20Vppinto50Ω

Thesignalrectificationisadesignfeatureofthecircuitanddoesnot indicateafaultcondition.

Adifferentkindofsoftoverdrivebehaviorhappensforlowimpedance loadshwenthecurrentlimitisreached. In this case, the amplifier willexhibitamonotonicsoftclipping behaviorasshownin figures 3.15 and 3.16.

Figure3.15:TheSIM954drivenwith1kHz trianglewaveto2A _pp into1Ω

Figure3.16: The SIM954 overdriven with 1kHz triangle waveto >2A pp into 1Ω

Ultimately, nearthesafetemperaturelimitforsilicondevices, the temperatureprotectioncircuitsinsideeachoperationalamplifierwill engageandshutthedevicedown.

Ifanapplicationrequireshardclipping,wesuggesttousetheSIM914 PreamplifierortheSIM964AnalogLimiter. TheSIM914willlimit atapproximately2Voutputsignallevel. Whencascadedwitha SIM954,itwillresultinapproximately8Vofclippingamplitude with3nsofinputrecoveryfromoverloadwhileproviding200MHz ofcombinedbandwidthwhileinlinearmode.

TheSIM964, ontheotherhand, allows 1MHz bandwidth and 10mV resolution for both upper and lower limits.

3.10 Miscellaneous Loads

TheSIM954wasspecificallydesignedwithdifficultlaboratoryloads inmind. Theseoftenincludelowimpedance,resonant,non-linear andtimevaryingloads.

3.10.1 HeatersandPeltierElements

TheSIM954canbeusedtodrivesmall(uptoapproximately5W) resistiveheatersandPeltierelementsinthermalcontrolapplications. Iftheamplifierspecificationscanpotentiallyexceedthemaximum heaterorPeltiervoltageorcurrent,theusermayaddexternalpro-tectioncircuitstoassurethesafetyoftheattachedload.

SincethisisanRFamplifier, it may be necessary to filter its output voltage with capacitors, inductors, beads or complex LC filter to prevent RF voltages from being radiated by unshielded loads.

3.10.2 Filaments

TheSIM954amplifiercanbeusedtodrivelowpowerfilaments, butcaremustbetakentoassurethatthefilamentcurrentandvoltagelimitarenotexceeded. Turn-onandturn-offtransientsdepend verymuchonthepowersupplyconfigurationandarenotlimited bydesign. Sensitive,unprotectedfilamentscanthereforebeeasily damagedordestroyed.

3.10.3 Driving Power MOSFETs

The SIM954 can be used to drive power MOSFETs with turn-on voltagesoflessthan10V,assumingthesourceofthedeviceisground referenced.

TheswitchingspeedoftheMOSFETwilldependonitsgatecharge whichisanonlinearfunctionofthegatevoltage. Atypicaldevice willexhibitastrongriseofgatechargeinasmallvoltageregion aroundtheturn-onvoltage.

If the MOSFETistobedriven with a fastrising edge, the current to deliver this chargeto the gate can exceed the output current of the amplifier. As a result, there is a minimum turn-on timewhich depends mostly on the output current capability of the amplifier. For atypical 10n C gate charge, this would be at least 10 ns (limited by the 1 A output current of the SIM954).

However, sincethegate will present large capacitance (ranging typically from tensof pico-Farad to tensof nano-Farad), event the inductance of short BNC cable (approximately 210 nH/mor 64 nH/foot)

willformaresonantLC-circuitwiththeMOSFET'sinputcapacitance.Itmightbenecessarytodampentheseresonanceswithadded seriesresistorsand/orRLCsnubbers.

Forexample,afoot(30cm)ofRG-58willresonantewitha100pFgate capacitanceataround50MHzandwouldrequirea20Ωdamping resistor,whilethreefeetofRG-58witha1000pFgatecapacitancepart willresonateataround9MHzandbehavereasonablywith5–10Ω ofadditionaldamping.

TheuserwhowishestodrivepowerMOSFETsisadvisedtoexperimentwithdifferentdriverconfigurationstofindtheoptimum combinationofcable,dampinganddevice.

3.10.4PiezoElements

TheSIM954outputvoltagelimitof10Vistoolowtodrivehigh voltageDCpiezoelements.However,themodulecandrivepiezo resonatorsverywell.Becauseithasalimitedoutputvoltage,the piezoelementhastobedriveneitherbyaseriesLCcircuit,atransformer,oracombinationofboth. Theunlimitedstabilitywillease theimpedancematchingofthedevicetotheamplifierconsiderably incomparisontoRFamplifierswithoutisolation.

3.10.5 Electric Motors

TheSIM954canbeusedtodrivesmallelectricmotors. Stepper motorsandlowvoltageasynchronousorsynchronousACmotors usuallypresentwellbehavedloadsandcanbedrivenbyaSIM954 aslongastheaverageandpeakcurrentdonotexceedtheamplifier's specifications.Becauseofthefastamplifierrisetimes,itisimportant tofiltertheSIM954outputwithbeadsandsmallceramiccapacitors beforeconnectingittounshieldedwires.Thesefiltershavetoacton thecommonmodeaswellasthedifferentialmodetomakesurethat possiblehighfrequencycomponentsgeneratedbytheSIM954are properlyattenuated. Limitingtherisetimeofthedrivingvoltages willgreatlyreducepossibleEMIproblems.

Unliketheiruncommutatedcounterparts, DCmotorswhichhave mechanicalorelectroniccommutatorscanproducevoltagespikes andsuddensurgecurrentswhich can degradeordamagetheamplifier. They should not be connected to a SIM954 without a detailed investigation into the nature of the electric behavior and proper filtering/overvoltage protection.

4Calibration

TheSIM954comesfullycalibratedandshouldnotexhibitmajor deteriorationofitspropertiesundernormaloperatingconditions.

Theusercan, however, re-calibratethemodule with relative easy and without excessiveriskofdegradingordamaging the product.

4.1 GettingReady

Therequired test equipment to trim the offset voltage and current of the SIM954 is a volt meter with 0.1 mV resolution.

4.2OffsetVoltageandInputBiasCurrent

EachofthetwoindependentamplifiersoftheSIM954hasoneoffset voltageandoneinputbiascurrenttrimmer. Theycanbeaccessed by removingthe(right)sidepanelofthemodulewhichisontheside closesttothefrontpanelLEDs.

The offset voltage and bias current trimmers R117, R198, R121 and R199 are located on the sparsely populated side of the PCB next to the twopowersupply limiter heatsinks. They have the following functions:

R117-offsetvoltagecompensationchannel1

R198-inputbiascurrentcompensationchannel1

R121-offsetvoltagecompensationchannel2

R199-inputbiascurrentcompensationchannel2

Sincetheinputbiascurrentisdifficulttomeasure, theprocedure trimsthe(proportional)inputoffsetvoltageinstead.

Step1: StartbyconnectingamV-metertotheinputofchannel1. The input offset voltage is then trimmed to 0mV with R117.

Step2: AfterconnectingthemV-metertotheoutputofchannel1, the output offset voltage can be trimmed to 0 mV with R198.

Iteration: Steps1 and 2 are repeated as many times necessary to trim both input and output offset voltage simultaneously to near 0 mV.

Thesameprocedureiscarriedoutforthesecondchannel:

Step3: The trim procedure starts by connecting am V-meter to the input of channel 2. The input offset voltage is then trimmed to 0 mV with R121.

Step4: AfterconnectingthemV-metertotheoutputofchannel2, the output offset voltage can be trimmed to 0 mV with R199.

Iteration:Steps3and4arerepeatedasmanytimesasnecessaryto trim both input and output offset voltage simultaneously to near 0 mV.

5PartsListsandSchematics

InThisChapter

5.1 CircuitDescription....5-2
5.2PartsLists....5-4
5.3SchematicDiagrams....5-7

5.1 CircuitDescription

TheSIM954containstwoindependentamplifiersandapowerconditioningcircuit.

Eachamplifierisprimarilymadeoutoffour250mAlinedriverop-amps(U101-U104andU105-U109).TheTHS3091/95familyofline driversaremadebyTexasInstrumentsusingarobust36VRFbipolar process.Insidethesmalloutlinepackagesthediesaresolderedtoa metalpadwhichisexposedonthebottomsideofpackages.These coolingpadsaredirectlysolderedtotheprintedcircuitboard,giving thepartunusualthermalloadhandlingcapability.

TheSIM954 exploit this unusually powerful part by paralleling four of them with 13.2Ω output resistors (R1x6a-d). These isolation resistors givethis amplifier excellent stability by adding a positive resistive component to all external passive loads. Even dead shorts and perfectly loss less capacitive and inductive loads are seen by the actual amplifier as adissipative load that liewell within its stability limits.

Because of the load-sharing each operational amplifier sees a worst caseload of 13.2 + Z Load × 4 . Specifically a load therefore appears as 213.2 Ω to each individual op-amp, which is a very benign load condition.

In addition, the resistors reduce the power dissipation of the op-amps incaseofverylowimpedanceloads(likeshortsandDCcurrents into coils/transformers) driven with large currents. At 1 A output the outputresistorswillabsorbavoltagedropof3.2Vorapproximately 20%ofthetotalthermalload.

Becauseoftheir3.3 Ωoutputimpedance,SIM954amplifierchannels canalsobegangedinparalleliftheyarebeingdrivenbythesame signal.Seesection2.1.2forfurtherdiscussion.

The THS3091/95 are current-feedback op-amps and the ideal gain and feedback configuration at which these amplifiers have their largest useful gain-bandwidth are as inverting amplifier with a gain between -4 and -5.

TheDCgainoftheamplifieristhereforechosensuchthatthe3.3Ω outputimpedancetogetherwiththe50 ΩinputimpedanceofatypicalRFsystemformadividerwhichreducestheeffectivegainto-4 or 12 dB. This means that the module will have a gain of -4.266 into ahighimpedanceload. Thisisequivalenttoa12.6 dBunterminated signalgain.

Depending on the variations in wafer lot each amplifier has a feed-back of 953–1100 Ω (R1x4) which makes the frequency response close

toflatandleadstoflattopsquarewaveresponse.

Toachivethedesiredgainwiththisfeedbackresistance,theinverting amplifierinputisconnectedtotheinputBNCthrougha221-255Ω resistor(R1x5).Inputinpedancematchingisachivedwithanadditionalresistortoground(R130,R131)

SincetheinputoffsetvoltagedriftoftheTHS3091isunsatisfactory,a slow precision amplifier (U111, U112)senses the average offset voltage ontheinvertinginputnodesandcorrectsitbyapplyingacorrection voltagetothenon-invertingpoweramplifierinputs. Theresultiung hybridamplifierhasbetteroffsetdriftcharacteristicsthantheRFop-ampsalone. Butsincethecancellationisdoneontheinputside,and notinasecondfeedbackloopfromtheoutput,theresidualdriftis higherthanonewouldexpectfromanidealhybridop-amp.

ThesecondartifactoftheTHS3091isitshighinputbiascurrent of 20 A , whichistypicalforhighspeedbipolaramplifiers. However, since the bias current drift is only on the order of 20nA / K , thebiascurrentcanbecompensatedwithaconstantcurrentsource. These current sources are formed by trimpots R198, R199 and resistors R107, R111, R101, R119. Additional capacitors suppress supply noise and increase common mode rejection for frequencies above approximately6Hz.

The output voltage of each amplifier is buffered by operational amplifiers U201 and U203. These buffers drive peak detectors Q201/202 and Q203/204.

The power supply current limiter uses MOSFETS Q301 and Q302 to limit the inrush current into capacitors C303 – 306. The voltage drop on sense resistors R305 and R311 opens transistors Q305 and Q307andlimitsthegatevoltageontheMOSFETstoapproximately 750 mA. As the necessary base-emitter voltages to open Q305 and Q307dropwithhighertemperature,thesetransistorsautomatically reducethecurrentatelevatedmoduletemperatures.

5.2PartsLists

Thepartslistisforreferenceonly, and subjecttochangewithout notice.

ItemQuantityPartReferencePartNumberValue

132C1x1C1x4C185C186C189C190C260-C2675-00299-100.1U
C301-C304
230C102C105C107-C110C112C115C122C1255-00525-1001U
C132C135C142C145C152C155C162C165
C172C175C184C187C188C191C204C254
C311-C314
32C192C1935-00525-1001U
44C201C202C251C252	5-00704-10033P
54C203C205C253C255	5-00387-1001000P
61	C207	5-00375-100100P
74	C208-C211	5-00298-100.01U
82C305C3065-00102-5174.7U
94	C307-C310	5-00201-0012200U
10	10	D101-D110	3-00896-145BAV99
11	2	D111D305	3-01357-142MMBZ5230
12	1	D203	3-00544-145	BAV70LT1
13	3	D204-D206	3-00424-160	GREEN, 3MM SUBM
14	4	D301-D304	3-00479-040MUR410
15	1	J1027-00966-721BNCBARRELSIM914
16	4	J103 J201 J202 J301	1-00471-002	4 PIN, WHITE
17	1	J1051-00109-0004PINDI
18	1	JP103	1-00367-04015PIND
19	7	L101-L103 L301-L304	6-00174-051	BEAD
20	4	Q201 Q202 Q251 Q252	3-00810-150	MMBTH10LT1
21	4	Q203 Q204 Q253 Q254	3-00809-150	MMBTH81LT1
22	6	Q205 Q206 Q208 Q209 Q255 Q256	3-01153-360	NDC7002N
23	3	Q207 Q305 Q307	3-00601-150	MMBT3904LT1
24	1	Q301	3-00944-053IRF4905
25	1	Q302	3-00283-053	IRF530/IRF532
26	3	Q303 Q304 Q306	3-00580-150	MMBT3906LT1
27	8	R101 R107 R109 R111 R119 R120 R194 R195	4-01280-110	49.9K
28	8	R102 R112 R122 R132 R142 R152 R162 R172	4-01447-100	47
29	8	R103 R113 R123 R133 R143 R153 R163 R173	4-00925-110	10
30	8	R104 R114 R124 R134 R144 R154 R164 R174	4-01115-110	953
31	8	R105 R115 R125 R135 R145 R155 R165 R175	4-01054-110	221
32	8	R106 R116 R126 R136 R146 R156 R166 R176	4-02468-110	3.3
33	8	R108 R118 R128 R138 R148 R158 R168 R178	4-01165-110	3.16k
34	4	R117 R121 R198 R199	4-00611-053	100K
35	2	R130R131	4-01090-110523
36	10	R180-R187 R196 R197	4-00993-110	51.1
37	2	R201R251	4-01174-1103.92K
38	2	R202R252	4-01448-10051
39	4	R203 R204 R253 R254	4-01163-110	3.01K
40	12	R205-R208 R218 R233 R237 R241 R255-R258	4-01117-110	1.00k
41	4R209-R212	4-01575-10010M
42	6R213-R215R263-R265	4-01551-1001.0M
43	2	R216R266	4-01120-1101.07K
44	4	R217 R232 R236 R240	4-01222-110	12.4K
45	4	R219 R234 R238 R242	4-00992-110	49.9
46	4	R220 R235 R239 R243	4-01128-110	1.30K

471R2214-01246-11022.1K

484R223R224R230R2314-01483-1001.5K

491R2274-01486-1002.0K

504R259-R2624-01575-10010M

514R301R302R308R3094-01431-10010

5211R304R307R313-R319R329R3304-01185-1105.11K

532R305R3114-00537-0201.0

543 R306R312R328

558R320-R3274-00935-11012.7

Electrical circuit diagram with labeled components including amplifiers, resistors, capacitors, and ICs for signal processing or control design.

	1	2	3
3			4
###			5

Reducing voltage and heat load on J303 R320 12.7 R321 12.7 R322 12.7 R323 12.7 U303 78L05 IN OUT C020 6-6-6 C311 1U C312 1U +5V D301 MUR410 D301 MUR410 C301 1U C301 IRF4905 R306 100K Shorting jumper J105 is used during calibration to test the current of the mosfet current limiter. 4 PIN DI J105 FS Isolation Between the two channels to reduce croista.k -15Va L303 BEAD 6-60174-051 C309 220U L302 BEAD 6-30174-051 C308 220U C305 4.7U 5-00102-517 C303 1U 5-00299-100 -15Vb L304 BEAD 6-30174-051 C310 220U C306 4.7U 5-00102-517 C304 1U 5-00299-100 D304 MUR410 D303 MUR410 R313 5.11K R314 5.11K R318 5.11K R319 5.11K R328 100K R329 5.11K R328 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT390SLT1 MMBT38MMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMMLMRL D305 MMBZS230 Fluxed in footscis of KJ83 Fluxes in footycrist of KJ83 Fluxes in footycrist of KJ83 Negative Current Limit R324 12.7 R325 12.7 R326 12.7 R327 12.7 U304 PLSO5 IN OUT IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN IN In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In In Ions D304 MUR410 D305 MMBT390QLT1 D306 MMBT390QLT1 D307 MMBT390QLT1 D308 MMBT390QLT1 D309 MMBT390QLT1 D310 MMBT390QLT1 D311 MUR410 D312 100K C302* 1U C302 IRF530IRF532 D302 MUR410 Reducing voltage and heat load on U304 Facts shown with a batched background are currently Eying leased SCSs

Friday.

TitleSIM954 Softstart
Size Document Number RevB		E
Date: Sheet	1 of 1

U101C THS3091/5 U102C THS3091/5 U103C THS3091/5 U104C THS3091/5 U201C THS3091/5 GND1 GND2 GND3 GND4 GND5 GND6 GND7 GND8 GND9 GND10 GND11 GND12 GND13 GND14 GND15 GND16 GND17 GND18 GND1 GND2 GND3 GND4 GND5 GND6 GND7 GND8 GND9 GND10 GND11 GND12 GND13 GND14 GND15 GND16 GND17 GND18

U105C THS3091.5 U106C THS3091.5 U107C THS3091.5 U108C THS3091.5 U203C THS3091.5 GND1 GND2 GND3 GND4 GND5 GND6 GND7 GND8 GND9 GND10 GND11 GND12 GND13 GND14 GND15 GND16 GND17 GND18 GND2 GND3 GND4 GND5 GND6 GND7 GND8 GND9 GND10 GND11 GND12 GND13 GND14 GND15 GND16 GND17 GND18 GND2 GND3 GND4 GND5 GND6 G ND7 GND8 GND9 GND10 GND11 GND12 GND13 GND14 GND15 GND16 GND17 GND18

Title SIM954 Power Pads
Size Document Number RevB		E
Date: Sheet	1 of 1