Alc271x Datasheet [updated] May 2026

The Definitive Guide to the ALC271X Datasheet: Pinouts, Specifications, and Legacy Audio Design

7. Ordering Information

| Part Number | Package | Temperature Range | |-------------|---------|-------------------| | ALC271X-VB | 48-pin LQFP (lead-free) | 0°C to +70°C | | ALC271X-VC | 48-pin QFN | -40°C to +85°C |

Chapter 5: Application Circuit – Reference Design

Page 45 of the standard alc271x datasheet shows the reference design. For a functional audio section, you need five external components besides the codec: alc271x datasheet

1. Crystal (X2): 24.576 MHz parallel resonant. The datasheet lists: Fox FS4B, ECS ECS-240-20-5PXDN-TR, or equivalent with 20pF loading caps.
2. Analog Power Filter: A 10uF tantalum + 0.1uF ceramic on AVDD (Pin 48).
3. VREF Filter: 2.2uF capacitor (low ESR, X7R) on Pin 2.
4. HP_DET (Jack Detection): This is optional but recommended. The datasheet uses a mechanical switch inside the headphone jack to pull Pin 33 (HP_DET) to ground.
5. ACZ_CAP (Analog Coupling): For the headphone output, a 220uF electrolytic capacitor in series with each channel (if DC-coupled headphone amp is not used).

Overview

The ALC271X is a family of low-power, high-integration audio codecs commonly used in laptops, tablets, and compact motherboards. It provides multi-channel analog output, mono/stereo inputs, integrated ADC/DAC, microphone bias, and typical PC audio features (HP amp, line-level I/O, digital interfaces). This deep post explains architecture, features, signal chain, programming, Linux and Windows driver considerations, hardware design tips, debugging, and tuning for audio quality. The Definitive Guide to the ALC271X Datasheet: Pinouts,

Example use cases

• Notebook audio subsystem: Notebook with internal speakers, stereo headphone, one or two microphones — requires jack detection, mic bias, and integrated HP amp tuning.
• Tablet: Low-power operation, deep-suspend states, and single-ended mic with tight power sequencing.
• Embedded board: External amplifier after codec line-out, requiring proper DC-coupling or blocking capacitors and level matching.

Chapter 2: Key Technical Specifications (From the Datasheet)

Before diving into circuit design, here are the absolute maximum ratings and DC characteristics you must extract from the official datasheet: Crystal (X2): 24

• Package: 48-pin LQFP (7mm x 7mm)
• Analog Supply (AVDD): 4.75V to 5.25V (Typ. 5V)
• Digital Supply (DVDD): 3.0V to 3.6V (Typ. 3.3V)
• Interface Type: HDA (Serial) or AC-link (for AC’97)
• DAC Performance:
  • Signal-to-Noise Ratio (SNR): 88 dB (A-Weighting)
  • Total Harmonic Distortion (THD): -75 dB
• ADC Performance:
  • SNR: 85 dB
  • THD: -70 dB
• Supported Sample Rates: 48 kHz, 44.1 kHz (with SRC to 48 kHz in HDA mode)
• Operating Temperature: 0°C to 70°C (Commercial grade)

Critical Note from the Datasheet: The ALC271X does not support 192 kHz sampling or 7.1 surround sound. It is strictly stereo line-out and stereo line-in/mic with a dedicated headphone amplifier.

Chapter 10: Troubleshooting Guide (Based on Datasheet Errata)

The voltage tolerances listed in the official alc271x datasheet are stringent. Here is a quick diagnostic table for the most common failures in the field:

| Symptom | Datasheet Diagnostic Step | Likely Fix | | :--- | :--- | :--- | | No audio, codec detected | Check RST# pin (Pin 8). Must be 3.3V after BIOS post. | Pull-up resistor to 3.3V is missing or blown. | | Popping on power on/off | Check VREF (Pin 2). Should ramp slowly to 2.5V. | Increase VREF cap to 4.7uF or use low-leakage cap. | | Loud hiss on headphones | Check AVDD (Pin 48) noise floor. Must be <10mV ripple. | Add ferrite bead (BLM21) in series with AVDD. | | One channel silent | Check coupling caps (Line-out pins). | DC offset is present. Replace 220uF series caps. | | No microphone detection | Check MICBIAS (Pin 39). Must be +5V via a 2.2k resistor. | MICBIAS trace is likely lifted or shorted. |

Driver integration

• Linux: ALC271-family codecs typically supported by snd_hda_intel / HDA codec drivers or ASoC machine drivers for SoC platforms. Use the codec’s pin widgets and DAPM paths in the ASoC driver. Implement jack detection callbacks and quirks for notebook-specific routing.
  • Confirm supported model ID; add quirk entries if platform wiring differs from reference.
  • Use ALSA mixer controls to expose mic boost, playback volume, and input muxing.
• Windows: Many OEMs use vendor-supplied HD-Audio drivers; customization done in driver INF and vendor-supplied codec module. Use vendor tools to map pins and define default routing.