3.3.3.1UsingLineOutputsin6-ChannelConfigurations
3.3.4RecoveryfromClockError
3.3.5Power-SupplyVolume-ControlEnable
3.3.6VolumeandMuteUpdateRate
3.3.7ModulationIndexLimit
TAS5518C
8-ChannelDigitalAudioPWMProcessor
SLES238A–SEPTEMBER2008–REVISEDJULY2009
www.ti.com
Theaudiosystemcanbeconfiguredfora6-channelconfiguration(with2lineouts)bywritinga1tobitD1
ofregister0xE0(generalcontrolregister).Inthisconfiguration,channel-5and-6processingareexactly
thesameastheotherchannels,exceptthatthemastervolumeandtheloudnessfunctionhavenoeffect
onthesignal.
Notethatin6-channelconfiguration,channels5and6areunaffectedbyback-enderror(BKND_ERR
goeslow).
Tousechannels5and6asunprocessedlineouts,thefollowingsetupisrecommended:
•Channel-5volumeandchannel-6volumeshouldbesetforaconstantoutput,suchas0dB.
•Bassandtrebleforchannels5and6canbeusedifdesired.
•DRC1shouldbebypassedforchannels5and6.
•Ifadownmixisdesiredonchannels5and6aslineout,thedownmixingcanbeperformedusingthe
channel-5andchannel-6inputmixers.
•Theoperationofthechannel-5and-6biquadsisunaffectedbythe6-/8-channelconfigurationsetting.
TheTAS5518Ccanbeseteithertoperformavolumerampupduringtherecoverysequenceofaclock
errororsimplytocomeupinthelaststate(ordesiredstateifavolumeortoneupdatewasinprogress).
ThisfeatureisenabledviaI
2
Csystemcontrolregister0x03.
Thepower-supplyvolumecontrol(PSVC)canbeenabledanddisabledviaI
2
Cregister0xE0.The
subwooferPWMoutputisalwayscontrolledbythePSVC.WhenusingPSVCthesubwoofercannotbe
usedaslineout.
TheTAS5518Chasfixedsoftvolumeandmuterampdurations.Therampsarelinear.Thesoftvolume
andmuterampratesareadjustablebyprogrammingtheI
2
Cregister0xD0fortheappropriatenumberof
stepstobe512,1024,or2048.Theupdateisperformedatafixedrateregardlessofthesamplerate.
•Innormalspeed,theupdaterateis1stepevery4/f
S
seconds.
•Indoublespeed,theupdateis1stepevery8/f
S
seconds.
•Inquadspeed,theupdateis1stepevery16/f
S
seconds.
Becauseofprocessorloading,theupdateratecanincreaseforsomeincrementsbyonestepevery1/f
S
to
3/f
S
.However,thevarianceofthetotaltimetogofrom18dBtomuteislessthan25%.
Table3-8.VolumeRampPeriodsinms
SAMPLERATE(kHz)
NUMBEROFSTEPS
44.1,88.2,176.432,48,96,192
51246.4442.67
102492.8885.33
2048185.76170.67
PWMmodulationisalinearfunctionoftheaudiosignal.Whentheaudiosignalis0,thePWMmodulation
is50%.Whentheaudiosignalincreasestowardfullscale,thePWMmodulationincreasestoward100%.
Fornegativesignals,thePWMmodulationsfallbelow50%toward0%.
However,themaximumpossiblemodulationdoeshavealimit.Duringtheofftimeperiod,thepowerstage
TAS5518CControlsandStatus 48SubmitDocumentationFeedback
Not Recommended For New Designs
