LM4545

AC ’97 Codec with Stereo Headphone Amplifier and

National 3D Sound

General Description

The LM4545 is an audio codec for PC systems which per-

forms the analog-intensive function of the Analog Codec ’97

Rev 1.03 Architecture. Using 18-Bit

Σ∆ A/D and D/A convert-

ers, the LM4545 provides 90dB of dynamic range.

The LM4545 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 A/D’s and D/A’s

and an analog mixer with 4 stereo and 3 mono inputs, each

of which has separate gain, attenuation and mute control. In

addition, the LM4545 provides a stereo headphone amplifier

with an independent gain control and National’s 3D Sound

stereo enhancement technology.

The LM4545 features AC-Link, a synchronous, fixed rate se-

rial bus for connection to the digital AC ’97 Controller. The

separation of the analog and digital functions of the AC ’97

architecture allows for system design flexibility and in-

creased overall performance.

Key Specifications

n Analog Mixer Dynamic Range

95dB (typ)

n D/A Dynamic Range

89dB (typ)

n A/D Dynamic Range

90dB (typ)

n Headphone THD+N at 50mW into 32

Ω

0.02% (typ)

Features

n Audio Codec ’97 compliant

n Stereo 18-Bit

Σ∆ A/D’s and D/A’s with 128X

oversampling

n Stereo headphone amp with separate gain control

n National’s 3D Sound circuitry

n Power management support

n Digital Interface 3V and 5V compliant

Applications

n Desktop PC Audio Systems

n Portable PC Audio Systems

n Mobile PC Audio Solutions

Block Diagram

DS100069-1

FIGURE 1. LM4545 Block Diagram

PRELIMINARY

July 1999

© 1999 National Semiconductor Corporation

DS100069

www.national.com