LM4546B

The LM4546B 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 LM4546B provides 90 dB of Dynamic Range.

The LM4546B 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 2 stereo and 2 mono inputs. Each mixer input has separate gain, attenuation and mute control and the mixers drive 1 mono and 1 stereo output, each with attenuation and mute control. The LM4546B supports Texas Instruments' 3D Sound stereo enhancement and a comprehensive sample rate conversion capability. The sample rate for the ADCs and DACs can be programmed separately with a resolution of 1 Hz to convert any rate in the range 4 kHz – 48 kHz. Sample timing from the ADCs and sample request timing for the DACs are completely deterministic to ease task scheduling and application software development. These features together with an extended temperature range also make the LM4546B suitable for non-PC codec applications.

The LM4546B features the ability to connect several codecs together using the Extended AC Link configuration of one dedicated serial data signal to the Controller per codec. LM4546B systems support up to 8 simultaneous channels of streaming data on Input Frames (Codec to Controller) while Output Frames (Controller to Codec) carry 2 streams to multiple codecs. The LM4546B may also be used in systems with the Texas Instruments LM4550 to support up to 6 simultaneous channels of streaming data on Output Frames.

The AC '97 architecture separates the analog and digital functions of the PC audio system allowing both for system design flexibility and increased performance.