Product details


Number of ADC channels 2 Number of DAC channels (#) 2 Digital audio interface I2S Analog inputs 7 Sampling rate (Max) (kHz) 48 Rating Catalog ADC SNR (Typ) (dB) 90 DAC SNR (Typ) (dB) 89 open-in-new Find other Audio CODECs

Package | Pins | Size

LQFP (PT) 48 81 mm² 9 x 9 open-in-new Find other Audio CODECs


  • AC ’97 Rev 2.1 Compliant
  • High Quality Sample Rate Conversion From 4 kHz
    to 48 kHz in 1 Hz Increments
  • Supports up to 6 DAC Channel Systems With
    Multiple LM4550Bs or With Other TI LM45xx
  • Unique TI Chaining Function Shares a Single
    Controller SDATA_IN Pin Among Multiple Codecs
  • Stereo Headphone Amp With Separate Gain Control
  • TI’s 3D Sound Stereo Enhancement Circuitry
  • Advanced Power Management Support
  • External Amplifier Power-Down (EAPD) Control
  • PC Beep Passthrough to Line Out During
    Initialization or Cold Reset
  • Digital 3.3-V and 5-V Supply Options
  • Extended Temperature: –40°C ≤ TA ≤ 85°C
  • Key specifications
    • Analog Mixer Dynamic Range, 97 dB (Typical)
    • DAC Dynamic Range, 89 dB (Typical)
    • ADC Dynamic Range, 90 dB (Typical)
    • Headphone Amp THD+N at 50 mW, 0.02%
      (Typical) into 32Ω
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The LM4550B device 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 LM4550B provides 90 dB of Dynamic Range.

The LM4550B 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 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 LM4550B provides a stereo headphone amplifier as one of its stereo outputs and also supports TI’s 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 from 4 kHz to 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 LM4550B suitable for non-PC codec applications.

The LM4550B features the ability to connect several codecs together in a system to provide up to 6 simultaneous channels of streaming data on output frames (controller to codec) for surround sound applications. Such systems can also support up to 8 simultaneous channels of streaming data on input frames (codec to controller). Multiple codec systems can be built either using the standard AC Link configuration (that is, of one serial data signal to the controller per codec) or using a unique TI feature for chaining codecs together. This chain feature shares only a single data signal to the controller among multiple codecs.

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

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Technical documentation

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Type Title Date
* Datasheet LM4550B AC '97 Rev 2.1 Multi-Channel Audio Codec With Stereo Headphone Amplifier, Sample Rate Conversion and TI 3D Sound datasheet (Rev. G) Sep. 11, 2015
Application note Out-of-Band Noise Measurement Issues for Audio Devices (Rev. A) Dec. 31, 2019
Application note Audio Serial Interface Configurations for Audio Codecs (Rev. A) Jun. 27, 2019
Application note Using the MSP430 Launchpad as a Standalone I2C Host for Audio Products (Rev. A) Oct. 28, 2013
Application note Audio Serial Interface Configurations for Audio Codecs Sep. 22, 2010
Application note Solving Enumeration Errors in USB Audio DAC and CODEC Designs Oct. 30, 2009
Application note Configuring I2S to Generate BCLK from Codec Devices & WCLK from McBSP Port Jul. 08, 2009

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