1 Features
1• AC '97 Rev 2.1 Compliant
• High Quality Sample Rate Conversion From 4 kHz
to 48 kHz in 1 Hz Increments
• Supports up to 6 DAC Channel Systems With
Multiple LM4550Bs or With Other TI LM45xx
Codecs
• Unique TI Chaining Function Shares a Single
Controller SDATA_IN Pin Among Multiple Codecs
• Stereo Headphone Amp With Separate Gain
Control
• TI'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)
– Headphone Amp THD+N at 50 mW, 0.02%
(Typical) into 32Ω

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 Audio Frequency Systems Requiring 2, 4
or 6 DAC Channels and/or up to 8 ADC Channels
• Automotive Telematics

3 Description
The LM4550B device is an audio codec for PC
systems which is fully PC99 compliant and performs the analog intensive functions of the AC '97 Rev 2.1
architecture. Using 18-bit Sigma-Delta ADCs and
DACs, the LM4550B provides 90 dB of Dynamic
Range.
The LM4550B 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.