LM4549 Datasheet | National Semiconductor

Description The LM4549 is an audio codec for PC systems which is fully PC98 pliant 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 90d B 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 4k Hz-48k Hz. 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 97d B (typ) 89d B (typ) 90d B (typ) Features n AC’97 Rev 2.1 pliant n National’s 3D Sound circuitry n High quality Sample Rate Conversion (SRC) from 4k Hz to 48k Hz in 1Hz increments. n Multiple Codec Support n External Amplifier Power Down (EAPD) control from codec n PC-Beep passthrough to Line Out while reset is held active low n True Line Level Output with volume control independent of Line Out n Digital 3V and 5V pliant Applications n Desktop PC Audio Systems on PCI cards, AMR cards, or with motherboard chips sets featuring AC-Link n Portable PC Systems as on MDC cards, or with a chipset or accelerator featuring AC-Link Block Diagram DS101035-1 FIGURE 1. LM4549 Block Diagram © 1999 National Semiconductor Corporation DS101035 .national. Absolute Maximum Ratings (Note 3) If Military/Aerospace specified devices are required,...