LM4548 Datasheet, PDF (1/18 Pages) National Semiconductor (TI) – AC ’97 Rev 2 Codec with Sample Rate Conversion and National 3D Sound

February 1999
LM4548
AC ’97 Rev 2 Codec with Sample Rate Conversion and
National 3D Sound
General Description
The LM4548 is an audio codec for PC systems which is fully
PC98 compliant and performs the analog intensive functions
of the AC97 Rev2 architecture. Using 18-bit Sigma-Delta
A/D’s and D/A’s, the LM4548 provides 90dB of Dynamic
Range.
The LM4548 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.
The LM4548 also provides the additional True Line-Level
output and National’s 3D Sound stereo enhancement.
The LM4548 supports variable sample rate conversion as
defined in the AC97 Rev2 specification. The sample rate for
the A/D and D/A can be programmed separately to convert
any rate between 4kHz - 48kHz with a resolution of 1Hz. The
AC97 architecture separates the analog and digital functions
of the PC audio system allowing both for system design flex-
ibility and increased performance.
Key Specifications
n Analog Mixer Dynamic Range
n D/A Dynamic Range
n A/D Dynamic Range
97dB (typ)
89dB (typ)
90dB (typ)
Features
n AC’97 Rev2 compliant
n National’s 3D Sound circuitry
n High quality Sample Rate Conversion (SRC) from 4kHz
to 48kHz in 1Hz increments.
n Multiple Codec Support
n True Line Level Output with volume control in addition to
standard Line Out
n Advanced power management support
n Digital 3V and 5V compliant
Applications
n Desktop PC Audio Systems
n Portable PC Systems
n Mobile PC Systems
Block Diagram
FIGURE 1. LM4548 Block Diagram
© 1999 National Semiconductor Corporation DS100987
DS100987-1
www.national.com