General Description
●The LM4550 is an audio codec for PC systems which is fully PC99 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 LM4550 provides 90 dB 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 con version. 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 kHz–48 kHz.
●Key Specifications
●Analog Mixer Dynamic Range 97dB (typ)
●D/A Dynamic Range 89dB (typ)
●A/D Dynamic Range 90dB (typ)
●Headphone Amp THD+N at 50 mW 0.02% (typ) into 32Ω
●Features
●AC’97 Rev 2.1 compliant
●Several LM4550s can be combined together for up to 6 channel operation
●Unique National chaining function allows multiple codecs to be connected serially and use only a single controller SDATA_IN pin
●High quality Sample Rate Conversion (SRC) from 4 kHz to 48 kHz in 1 Hz increments.
●Stereo headphone amp with separate gain control
●National’s 3D Sound circuitry
●External Amplifier Power Down (EAPD) control from codec
●PC-Beep passthrough to Line Out while reset is held active low
●Digital 3.3V and 5V compliant
●Applications
●Desktop PC audio systems on PCI cards, AMR cards, or with motherboard chips sets featuring AC-Link
●Portable PC systems as on MDC cards, or with a chipset or accelerator featuring AC-Link
●2, 4, or 6 channel systems
