LM4549

LM4549 AC ’97 Rev 2.1 Codec with Sample Rate Conversion and National 3D Sound February 1999 LM4549 AC ’97 Rev 2.1 Codec with Sample Rate Conversion and National 3D Sound General Description The LM4549 is an audio codec for PC systems which is fully PC98 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 LM4549 provides 90dB of Dynamic Range. The LM4549 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 codec features a second Line Output known as True Line Level Out that is identical to Line Out but with independent volume control. The LM4549 also features 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 1Hz to convert any rate between 4kHz-48kHz. The AC97 architecture separates the analog and digital functions of the PC audio system allowing both for system design flexibility 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 Rev 2.1 compliant n National’s 3D Sound circuitry n High quality Sample Rate Conversion (SRC) from 4kHz to 48k...