LM4549B Datasheet, PDF (1/28 Pages) National Semiconductor (TI) – AC ’97 Rev 2.1 Multi-Channel Audio Codec with Sample Rate Conversion and National 3D Sound

September 2006
LM4549B
AC ’97 Rev 2.1 Multi-Channel Audio Codec with Sample
Rate Conversion and National 3D Sound
General Description
The LM4549B is an audio codec for PC systems which is
fully PC99 compliant and performs the analog intensive
functions of the AC ’97 Rev 2.1 architecture. Using 18-bit
Sigma-Delta ADCs and DACs, the LM4549B provides 90 dB
of Dynamic Range.
The LM4549B was designed specifically to provide a high
quality audio path and provide all analog functionality in a PC
audio system. It features full duplex stereo ADCs and DACs
and analog mixers with access to 4 stereo and 4 mono
inputs. Each mixer input has separate gain, attenuation and
mute control and the mixers drive 1 mono and 2 stereo
outputs, each with attenuation and mute control. The
LM4549B supports National’s 3D Sound stereo enhance-
ment and a comprehensive sample rate conversion capabil-
ity. The sample rate for the ADCs and DACs can be pro-
grammed separately with a resolution of 1 Hz to convert any
rate in the range 4 kHz – 48 kHz. Sample timing from the
ADCs and sample request timing for the DACs are com-
pletely deterministic to ease task scheduling and application
software development. These features together with an ex-
tended temperature range also make the LM4549B suitable
for non-PC codec applications.
The LM4549B features the ability to connect several codecs
together using the Extended AC Link configuration of one
dedicated serial data signal to the Controller per codec.
LM4549B systems support up to 8 simultaneous channels of
streaming data on Input Frames (Codec to Controller) while
Output Frames (Controller to Codec) carry 2 streams to
multiple codecs. The LM4549B may also be used in systems
with the National LM4550B to support up to 6 simultaneous
channels of streaming data on Output Frames.
The AC ’97 architecture separates the analog and digital
functions of the PC audio system allowing both for system
design flexibility and increased performance.
Key Specifications
n Analog Mixer Dynamic Range
n DAC Dynamic Range
n ADC Dynamic Range
97 dB (typ)
89 dB (typ)
90 dB (typ)
Features
n AC ’97 Rev 2.1 compliant
n High quality Sample Rate Conversion from 4 kHz to 48
kHz in 1 Hz increments
n Multiple codec support
n True Line Level Output with separate gain control
n National’s 3D Sound stereo enhancement circuitry
n Advanced power management support
n External Amplifier Power Down (EAPD) control
n PC-Beep passthrough to Line Out during Initialization or
Cold Reset
n Digital 3.3V and 5V supply options
n Extended Temperature: −40˚C ≤ T_A ≤ 85˚C
Applications
n Desktop PC audio systems on PCI cards, AMR cards, or
with motherboard chips sets featuring AC Link
n Portable PC systems as on MDC cards, or with a
chipset or accelerator featuring AC Link
n General and Multi-channel audio frequency systems
n Automotive Telematics
© 2006 National Semiconductor Corporation DS201235
www.national.com