Advanced AC'97 Rev 2.3 Audio CODEC

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The ALC203 is a 20-bit DAC and 18-bit ADC full-duplex AC'97 2.3 compatible stereo audio CODEC designed for PC multimedia systems, including host/soft audio, and AMR/CNR based designs.

The ALC203 incorporates proprietary converter technology to achieve a high SNR (greater than 100 dB), sensing logics for device reporting, and a Universal Audio Jack® for improved user convenience. The ALC203 AC'97 CODEC supports multiple CODEC extensions with independent variable sampling rates and built-in 3D effects. The ALC203 CODEC provides two pairs of stereo outputs with independent volume controls, a mono output, multiple stereo and mono inputs, along with flexible mixing, gain, and mute functions to provide a complete integrated audio solution for PCs.

The circuitry of the ALC203 CODEC operates from a 3.3V digital and 3.3V/5V analog power supply with EAPD (External Amplifier Power Down) control for use in notebook and PC applications. The ALC203 integrates a 50mW/20Ohm headset audio amplifier into the CODEC, saving BOM costs. The ALC203 also supports the S/PDIF out function (complies with AC'97 2.3) that offers easy connection of PCs to consumer electronic products, such as AC3 decoders/speakers and mini disk devices.

The ALC203 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 (Win98/ME/NT/2000/XP, EAX/Direct Sound 3D/I3DL2/A3D compatible sound effect utilities (supporting Karaoke, 26-kinds of environment sound emulation, 10-band equalizer), HRTF 3D positional audio and Sensaura™ 3D (optional) provide an excellent entertainment package and game experience for PC users. An internal 14.318MHz -> 24.576MHz PLL circuit generates required timing signals, eliminating the need for external crystal, whilst a built-in PCBEEP generator removes the need for an external buzzer.

Realtek alc203_001.jpg

Symmetry Electronics (and its e-commerce division: is an authorized Realtek distributor.


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Single chip with high S/N ratio (>100 dB)
Meets performance requirements for audio on PC2001 systems
Meets Microsoft WHQL/WLP 2.0 audio requirements
20-bit DAC and 18-bit ADC resolution
18-bit Stereo full-duplex CODEC with independent and variable sampling rate
Complies with AC'97 2.3 specifications
- LINE/HP-OUT, MIC-IN and LINE-IN sensing
- 14.318MHz -> 24.576MHz PLL saves crystal
- 12.288MHz BITCLK input can be consumed
- Integrated PCBEEP generator to save buzzer
- Interrupt capability
- Page registers and Analog Plug & Play
Support of S/PDIF out is fully compliant with AC'97 rev2.3 specifications
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 input: PCBEEP, PHONE-IN
Supports double sampling rate (96KHz) of DVD audio playback
Two software selectable MIC inputs
+6/12/20/30dB boost preamplifier for MIC input
Stereo output with 6-bit volume control
Mono output with 5-bit volume control
Headphone output with 50mW/20Ohm amplifier
3D Stereo Enhancement
Multiple CODEC extension capability
External Amplifier Power Down (EAPD) capability
Power management and enhanced power saving features
Stereo MIC record for AEC/BF application
DC Voltage volume control
Auxiliary power to support Power Off CD
Adjustable VREFOUT control
2 GPIO pins with smart GPIO volume control
2 Universal Audio Jacks (UAJ) for front panel
Supports 32K/44.1K/48K/96KHz S/PDIF output
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 3D Enhancement (optional)
10 Bands of Software Equalizer
Voice Cancellation and Key Shifting in Kareoke mode
AVRack Media Player


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