1 Features
1• Compliant With AC '97 Rev 2.1
• High-Quality Sample Rate Conversion from 4 kHz
to 48 kHz in 1-Hz Increments
• Multiple Codec Support
• True Line Level Output with Separate Gain
Control
• Texas Instrument's 3D Sound Stereo
Enhancement Circuitry
• Advanced Power Management Support
• External Amplifier Power Down (EAPD) Control
• PC-Beep Passthrough to Line Out During
Initialization or Cold Reset
• Digital 3.3-V and 5-V Supply Options
• Extended Temperature: −40°C ≤ TA ≤ 85°C
• Key Specifications
– Analog Mixer Dynamic Range: 97 dB (Typical)
– DAC Dynamic Range: 89 dB (Typical)
– ADC Dynamic Range: 90 dB (Typical)

2 Applications
• Desktop PC Audio Systems on PCI Cards, AMR
Cards, or With Motherboard Chips Sets Featuring
AC Link
• Portable PC Systems as on MDC Cards, or With a
Chipset or Accelerator Featuring AC Link
• General and Multichannel Audio Frequency
Systems
• Automotive Telematics

3 Description
The LM4549B device is an audio codec for PC
systems which is fully compliant with the PC99 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 Texas Instrument's 3D Sound stereo enhancement and a comprehensive sample
rate conversion capability. The sample rate for the
ADCs and DACs can be programmed 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 completely
deterministic to ease task scheduling and application
software development. These features together with
an extended temperature range also make the
LM4549B suitable for non-PC codec applications.