LM4550 Datasheet | National Semiconductor

Description The LM4550 is an audio codec for PC systems which is fully PC99 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 LM4550 provides 90 d B 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 k Hz- 48 k Hz. 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 data stream to the controller. 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 n n n Analog Mixer Dynamic Range D/A Dynamic Range A/D Dynamic Range Headphone Amp THD+N at 50 m W into 32Ω 97d B 89d B 90d B 0.02% (typ) (typ) (typ) (typ) Features n AC’97 Rev 2.1 pliant n Several LM4550s can be bined together for up to 6 channel operation n Unique National chaining function allows multiple codecs to be connected serially and use only a single controller SDATA_IN pin n High quality Sample Rate Conversion (SRC) from 4 k Hz to 48 k Hz in 1 Hz increments. n Stereo headphone amp with separate gain control n National’s 3D Sound circuitry n External...