LM4540

LM4540 AC ’97 Codec with National 3D Sound February 1999 LM4540 AC ’97 Codec with National 3D Sound General Description The LM4540 is an audio codec for PC systems which performs the analog-intensive function of the Analog Codec ’97 Rev 1.03 architecture. Using 18-Bit Σ∆ A/D and D/A converters, the LM4540 provides 90dB of dynamic range. The LM4540 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 2 stereo and 3 mono inputs, each of which has separate gain, attenuation and mute control. In addition, the LM4540 provides National’s 3D Sound stereo enhancement technology. The LM4540 features AC-Link, a synchronous, fixed rate serial bus for connection to the digital AC ’97 Controller. The separation of the analog and digital functions of the AC ’97 architecture allows for system design flexibility and increased overall performance. Key Specifications n Analog Mixer Dynamic Range n D/A Dynamic Range n A/D Dynamic Range 95dB (typ) 89dB (typ) 90dB (typ) Features n Audio Codec ’97 compliant n Stereo 18-Bit Σ∆ A/D’s and D/A’s with 128X oversampling n National’s 3D Sound circuitry n Power management support n Digital Interface 3V and 5V compliant Applications n PC Audio Systems Requiring Only 2 Stereo Inputs (CD, Line) and 3 Mono Inputs (Mic, Phone, PC Beep) Block Diagram DS100906-1 FIGURE 1. LM4540 Block Diagram © 1999 National Semico...