AC'97 Rev 2.3 Audio CODEC

General Description

The ALC655 is a 16-bit, full-duplex AC'97 Rev. 2.3 compatible six-channel audio CODEC designed for PC multimedia systems, including host/soft audio and AMR/CNR-based designs.

The ALC655 incorporates proprietary converter technology to meet performance requirements for PC99/2001 systems. The ALC655 CODEC provides three pairs of stereo outputs with 5-bit volume control, a mono output, and multiple stereo and mono inputs, along with flexible mixing, gain, and mute functions to provide a complete integrated audio solution for PCs.

The digital interface circuitry of the ALC655 CODEC operates from a 3.3V power supply for use in notebook and PC applications. An integrated 50mW/20ohm headset audio amplifier for Front-Out and Surround-Out, a 14.318MHz -> 24.576MHz PLL, and a PCBEEP generator cut BOM costs. The ALC655 also supports S/PDIF input and output for easy connection of PCs to consumer electronic products, such as AC3 decoders/speakers and mini-disk devices. 

The ALC655 CODEC supports host/soft audio from Intel ICHx chipsets as well as audio controller-based VIA/SIS/ALI/AMD/nVIDIA/ATI chipsets. Bundled Windows series drivers (98/ME/NT/2000/XP), EAX/Direct Sound 3D/ I3DL2/A3D compatible sound effect utilities (supporting Karaoke, 26 types of environment sound emulation, 10-band equalizer), HRTF 3D positional audio and Sensaura 3DPA (optional) provide an excellent entertainment package and game experience for PC users. In addition, the ALC655 is embedded with an impedance sensing capability to detect when a device has been connected to input or output jacks.


  • Meets performance requirements for audio on PC99/2001 systems
  • Meets Microsoft WHQL/WLP 2.0 audio requirements
  • 16-bit Stereo full-duplex CODEC with 48KHz sampling rate
  • Compatible with AC'97 Rev 2.3 specifications
    • Front-Out, Surround-Out, MIC-In and LINE-In Jack Sensing
    • 14.318MHz -> 24.576MHz PLL to eliminate crystal
    • 12.288MHz BITCLK input
    • Integrated PCBEEP generator to save buzzer
    • Interrupt capability
  • Three analog line-level stereo inputs with 5-bit volume control, LINE_IN, CD, AUX
  • High-quality differential CD input
  • Two analog line-level mono inputs: PCBEEP, PHONE-IN
  • Two software selectable MIC inputs
  • Dedicated Front-MIC input for front panel applications (software selectable)
  • Boost preamplifier for MIC input
  • LINE input shared with surround output; MIC input shared with Center and LFE output
  • Built-in 50mW/20ohm amplifier for both Front-out and Surround-Out
  • External Amplifier Power Down (EAPD) capability
  • Power management and enhanced power saving features
  • Supports Power-Off CD function
  • Adjustable VREFOUT control
  • Supports 48KHz S/PDIF output, compatible with AC'97 Rev 2.3 specifications
  • Supports 32K/44.1K/48KHz S/PDIF input
  • Power support: Digital: 3.3V; Analog: 3.3V/5V
  • Standard 48-pin LQFP package
  • EAX™ 1.0 & 2.0 compatible
  • Direct Sound 3D™ compatible
  • A3D™ compatible
  • I3DL2 compatible
  • HRTF 3D positional audio
  • Sensaura™ 3DPA enhancement (optional)
  • 10-band software equalizer
  • Voice cancellation and key shifting in Karaoke mode
  • AVRack® Media Player
  • Configuration Panel for improved user convenience


  • Multimedia PCs
  • 3D PC games
  • Information appliances (IA)
  • Voice recognition
  • Audio conferencing