The product is an audio codec that can provide 18-bit Sigma-Delta ADCs and DACs, providing 90dB of dynamic range. The product is designed specifically for PC audio systems, with full duplex stereo ADCs and DACs and analog mixers that can access 4 stereo and 4 mono inputs. Each mixer input has separate gain, attenuation and mute control, and the mixers drive 1 mono and 2 stereo outputs, each with attenuation and mute control. The product also supports National’s 3D Sound stereo enhancement and a comprehensive sample rate conversion capability. The ADCs and DACs’ sample rates can be programmed separately with a resolution of 1Hz to convert any rate in the range 4kHz-48kHz. ADCs’ sample timing and DACs’ sample request timing are completely deterministic to ease task scheduling and application software development. These features and the extended temperature range also make the LM4550B suitable for non-PC codec applications. The product has the ability to connect multiple codecs together in a system to provide up to 6 equivalent stereo audio channels.
The LM4550B is an AC ’97 Rev 2.1 audio codec designed for PC audio systems. It offers 18‑bit Sigma‑Delta ADCs and DACs, full‑duplex stereo operation, analog mixers with separate gain and mute controls, a stereo headphone amplifier, and National’s 3D Sound enhancement.
Key specifications include a 90 dB ADC dynamic range, 89 dB DAC dynamic range, 97 dB analog‑mixer dynamic range, and sample‑rate conversion from 4 kHz to 48 kHz in 1 Hz steps. The device supports up to six simultaneous DAC channels or eight ADC channels and can be chained with multiple codecs using a single controller data line. It operates from –40 °C to 85 °C and is supplied with 3.0 V–5.5 V digital and 3.0 V–5.5 V analog rails.
| Analog Mixer Dynamic Range | 97 dB (typ) |
|---|---|
| DAC Dynamic Range | 89 dB (typ) |
| ADC Dynamic Range | 90 dB (typ) |
| Headphone Amp THD+N at 50 mW | 0.02 % (typ) |
| Sample‑Rate Conversion Range | 4 kHz – 48 kHz in 1 Hz steps |
| Operating Temperature Range | -40 °C – 85 °C |
| Maximum Simultaneous DAC Channels | 6 |
The ADC dynamic range is typically 90 dB.
The device can support up to six simultaneous DAC channels.
It operates from –40 °C to 85 °C.