Datasheet

h
BTL
+
p 2 P
L
R
L
Ǹ
4 V
DD
Therefore,
(11)
T
A
Max + T
J
Max * Θ
JA
P
Dmax
+ 125 * 113
(
0.634
)
+ 53.3°C
(14)
PCBLAYOUT
P
D max
+
2 V
2
DD
p
2
R
L
(12)
Θ
JA
+
1
Derating Factor
+
1
0.0088
+ 113°CńW
(13)
TPA6205A1
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..............................................................................................................................................................SLOS490BJULY2006REVISEDJUNE2008
temperature,andthemaximuminternaldissipation,
themaximumambienttemperaturecanbecalculated
withthefollowingequation.Themaximum
recommendedjunctiontemperatureforthe
TPA6205A1is125°C.
Table2.EfficiencyandMaximumAmbient
TemperaturevsOutputPowerin5-V8-BTL
Systems
Equation14showsthatthemaximumambient
PowerMax
OutputInternal
temperatureis53.3°Catmaximumpowerdissipation
EfficiencyFromAmbient
PowerDissipation
witha5-Vsupply.
(%)SupplyTemperature
(W)(W)
(W)(°C)
Table2showsthatformostapplicationsnoairflowis
0.2531.40.550.7562
requiredtokeepjunctiontemperaturesinthe
0.5044.40.621.1254
specifiedrange.TheTPA6205A1isdesignedwith
1.0062.80.591.5958
thermalprotectionthatturnsthedeviceoffwhenthe
junctiontemperaturesurpasses150°Ctoprevent
1.2570.20.531.7865
damagetotheIC.Also,usingmoreresistivethan8-
Table2employsEquation11tocalculateefficienciesspeakersdramaticallyincreasesthethermal
forfourdifferentoutputpowerlevels.Notethattheperformancebyreducingtheoutputcurrent.
efficiencyoftheamplifierisquitelowforlowerpower
levelsandrisessharplyaspowertotheloadis
increasedresultinginanearlyflatinternalpower
FortheDRB(QFN/SON)andDGN(MSOP)
dissipationoverthenormaloperatingrange.Notethat
packages,itisgoodpracticetominimizethe
theinternaldissipationatfulloutputpowerisless
presenceofvoidswithintheexposedthermalpad
thaninthehalfpowerrange.Calculatingthe
interconnection.Totaleliminationisdifficult,butthe
efficiencyforaspecificsystemisthekeytoproper
designoftheexposedpadstenciliskey.Thestencil
powersupplydesign.Fora1.25-Waudiosystemwith
designproposedintheTexasInstrumentsapplication
8-loadsanda5-Vsupply,themaximumdrawon
note"QFN/SONPCBAttachment"(SLUA271)
thepowersupplyisalmost1.8W.
enablesout-gassingofthesolderpasteduringreflow
AfinalpointtorememberaboutClass-ABamplifiers
aswellasregulatingthefinishedsolderthickness.
ishowtomanipulatethetermsintheefficiency
Typicallythesolderpastecoverageisapproximately
equationtotheutmostadvantagewhenpossible.
50%ofthepadarea.
NotethatinEquation11,V
DD
isinthedenominator.
InmakingthepadsizefortheBGAballs,itis
ThisindicatesthatasV
DD
goesdown,efficiencygoes
recommendedthatthelayoutusesolder-
up.
mask-defined(SMD)land.Withthismethod,the
Asimpleformulaforcalculatingthemaximumpower
copperpadismadelargerthanthedesiredlandarea,
dissipated,P
Dmax
,maybeusedforadifferential
andtheopeningsizeisdefinedbytheopeninginthe
outputapplication:
soldermaskmaterial.Theadvantagesnormally
associatedwiththistechniqueincludemoreclosely
controlledsizeandbettercopperadhesiontothe
laminate.Increasedcopperalsoincreasesthe
thermalperformanceoftheIC.Bettersizecontrolis
P
Dmax
fora5-V,8-systemis634mW.
theresultofphotoimagingthestencilsformasks.
Smallplatedviasshouldbeplacednearthecenter
Themaximumambienttemperaturedependsonthe
ballconnectingballB2tothegroundplane.Added
heatsinkingabilityofthePCBsystem.Thederating
platedviasandgroundplaneactasaheatsinkand
factorforthe2mmx2mmMicrostarJunior™
increasethethermalperformanceofthedevice.
packageisshowninthedissipationratingtable.
Figure35showstheappropriatediametersfora2
Convertingthistoθ
JA
:
mm×2mmMicroStarJunior™BGAlayout.
ItisveryimportanttokeeptheTPA6205A1external
componentsveryclosetotheTPA6205A1tolimit
Givenθ
JA
,themaximumallowablejunction
noisepickup.TheTPA6205A1evaluationmodule
(EVM)layoutisshowninthenextsectionasalayout
example.
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