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LM4549AVH-LM4549AVHX
AC '97 Rev 2.1 Codec with Sample Rate Conversion and National 3D Sound
LM4549A ’97 Rev 2.1 Multi-Channel Audio Codec with Sample
Rate Conversion and National 3D Sound
General DescriptionThe LM4549Aisan audio codecfor PC systems whichis
fully PC99 compliant and performs the analog intensive
functionsof the AC ’97 Rev 2.1 architecture. Using 18-bit
Sigma-Delta ADCs and DACs,the LM4549A provides90dB Dynamic Range.
The LM4549A was designed specificallyto providea high
quality audio path and provideall analog functionalityinaPC
audio system.It featuresfull duplex stereo ADCs and DACs
and analog mixers with accessto4 stereo and4 mono
inputs. Each mixer input has separate gain, attenuation and
mute control and the mixers drive1 mono and2 stereo
outputs, each with attenuation and mute control. The
LM4549A supports National’s 3D Sound stereo enhance-
ment anda comprehensive sample rate conversion capabil-
ity. The sample ratefor the ADCs and DACs canbe pro-
grammed separately witha resolutionof1Hzto convert any
ratein the range4 kHz–48 kHz. Sample timing from the
ADCs and sample request timingfor the DACs are com-
pletely deterministicto ease task scheduling and application
software development. These features together withan ex-
tended temperature range also makethe LM4549A suitable
for non-PC codec applications.
The LM4549A featuresthe abilityto connect several codecs
together using the Extended AC Link configurationof one
dedicated serial data signalto the Controller per codec.
LM4549A systems supportupto8 simultaneous channelsof
streaming dataon Input Frames (Codecto Controller) while
Output Frames (Controllerto Codec) carry2 streamsto
multiple codecs. The LM4549A may alsobe usedin systems
with the National LM4550to supportupto6 simultaneous
channelsof streaming dataon Output Frames.
The AC ’97 architecture separates the analog and digital
functionsof thePC audio system allowing bothfor system
design flexibility and increased performance.
Key Specifications Analog Mixer Dynamic Range 97dB (typ) DAC Dynamic Range 89dB (typ) ADC Dynamic Range 90dB (typ)
Features AC’97 Rev2.1 compliant High quality Sample Rate Conversion from4 kHzto48
kHzin1Hz increments Multiple codec support True Line Level Output with separate gain control National’s3D Sound stereo enhancement circuitry Advanced power management support External Amplifier Power Down (EAPD) control PC-Beep passthroughto Line Out during Initializationor
Cold Reset Digital 3.3V and5V supply options Extended Temperature: −40˚C≤TA≤ 85˚C
Applications DesktopPC audio systemson PCI cards, AMR cards,or
with motherboard chips sets featuringAC Link Portable PC systemsason MDC cards,or witha
chipsetor accelerator featuringAC Link General and Multi-channel audio frequency systems
May 2004
LM4549A
’97
Rev
Multi-Channel
Audio
Codec
with
Sample
Rate
Conversion
and
Sound
