LM4550

LM4550 AC ’97 Rev 2.1 Multi-Channel Audio Codec with Stereo Headphone Amplifier, Sample Rate Conversion and National 3D Sound December 2002 LM4550 AC ’97 Rev 2.1 Multi-Channel Audio Codec with Stereo Headphone Amplifier, Sample Rate Conversion and National 3D Sound General Description The LM4550 is an audio codec for PC systems which is fully PC99 compliant and performs the analog intensive functions of the AC97 Rev2.1 architecture. Using 18-bit Sigma-Delta A/D’s and D/A’s, the LM4550 provides 90 dB of Dynamic Range. The LM4550 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 LM4550 provides a stereo headphone amplifier with an independent gain control and also supports National’s 3D Sound stereo enhancement and variable sample rate conversion. The sample rate for the A/D and D/A can be programmed separately with a resolution of 1 Hz to convert any rate between 4 kHz–48 kHz. The LM4550 features the ability to connect several codecs together in a system to provide up to six channels for surround sound applications. Multiple codec systems can be built using the standard AC-Link format of one serial data stream per codec, or using a unique National Semiconductor feature for chaining codecs together. This chain feature requires only a single ...