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.