Version: 2.0  

Last updated: 2026-09-28

## Overview

This specification module outlines the hardware requirements for 3.5mm audio
connectors.


### Minimum and Additional Requirements

This specification document is divided into two sections:

1. **Minimum** requirements describe the criteria for a peripheral category to be compatible.
2. **Additional** requirements describe the criteria for certification.

Use these navigation buttons to show only the minimum or both the minimum
and additional specification, respectively.
<button value="min">Minimum</button> <button value="add" default="">Minimum and Additional</button>

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## 3.5mm audio connector hardware specifications

### MINIMUM REQUIREMENTS

#### Plug

- Mechanical
  - 4 conductor 3.5mm plug
  - Pinout order
    - CTIA (LRGM) - Recommended
    - OMTP (LRMG) - Optional
- Electrical
  - Ear speaker impedance
    - ≥ 16 Ω
  - Mic equivalent DC resistance
    - ≥ 1000 Ω

#### Buttons

- Only the following buttons are allowed:
  - Play or Pause (Function A)
  - Volume up (Function B)
  - Volume down (Function C)
- The control function equivalent Impedance\* MUST satisfy the requirements in
  the following table:

  | Function | Impedance^[1](https://developers.google.com/chromeos/peripherals/modules/cc-audio-35mm#fn1)^ range |
  |---|---|
  | Play or Pause (Function A) | \[0, 70\] Ω |
  | Volume up (Function B) | \[210, 290\] Ω |
  | Volume down (Function C) | \[370, 680\] Ω |

### ADDITIONAL REQUIREMENTS

Along with the **Minimum** requirements, a peripheral MUST meet the following
requirements to achieve certification:

#### Buttons

- **\[Mandatory\]** The audio device MUST NOT support the answer or hang up button, the OS does not support it.

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## Revision history

| Date | Version | Notes |
|---|---|---|
| 2026-09-28 | 2.0 | Update for ChromeOS Compatible specification. |
| 2026-03-03 | 1.3.2 | Formatting update. |
| 2024-06-14 | 1.3.1 | Use Ω for Ohms. Publish to partner site. |
| 2024-05-10 | 1.3 | Add Just Work requirement. |
| 2023-04-24 | 1.2 | Revise word usage. |
| 2022-09-03 | 1.1 | Add different requirement for 3.5mm Output Frequency Response. |
| 2022-12-19 | 1.0 | Initial version. |

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1. The equivalent impedance is measured from positive mic terminal to GND
   when button is pressed with 2.2 V mic bias applied through 2.2 kΩ resistor. [↩](https://developers.google.com/chromeos/peripherals/modules/cc-audio-35mm#fnref1)