LM4540 Datasheet, PDF (1/16 Pages) National Semiconductor (TI) – AC ’97 Codec with National 3D Sound

February 1999
LM4540
AC ’97 Codec with National 3D Sound
General Description
The LM4540 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 LM4540 provides 90dB of dynamic range.
The LM4540 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 2 stereo and 3 mono inputs, each
of which has separate gain, attenuation and mute control. In
addition, the LM4540 provides National’s 3D Sound stereo
enhancement technology.
The LM4540 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
n D/A Dynamic Range
n A/D Dynamic Range
95dB (typ)
89dB (typ)
90dB (typ)
Features
n Audio Codec ’97 compliant
n Stereo 18-Bit Σ∆ A/D’s and D/A’s with 128X
oversampling
n National’s 3D Sound circuitry
n Power management support
n Digital Interface 3V and 5V compliant
Applications
n PC Audio Systems Requiring Only 2 Stereo Inputs (CD,
Line) and 3 Mono Inputs (Mic, Phone, PC Beep)
Block Diagram
FIGURE 1. LM4540 Block Diagram
© 1999 National Semiconductor Corporation DS100906
DS100906-1
www.national.com