M.2 (NGFF) Connector Pinout & Keys Explained

The M.2 standard, formerly known as Next Generation Form Factor (NGFF), is a versatile specification for internally mounted computer expansion cards. It was designed to replace the mSATA standard and is used for a wide variety of devices, including Wi-Fi, Bluetooth, WWAN (cellular), GPS, NFC, and most notably, Solid State Drives (SSDs).

M.2 Module Keys and Sockets

M.2 modules feature notches (keys) that correspond to different socket types on the motherboard or host device. These keys prevent incorrect insertion and ensure compatibility. A single M.2 card can have one or more notches.

The keying is defined by which pins are "missing" or "notched out" on the 75-pin edge connector. Here are the most common keys and their typical applications:

M.2 Form Factors & Mechanics

M.2 module sizes are commonly expressed as a four- or five-digit code in the form WWLL (e.g., 2280), where WW is the width in millimeters and LL is the length in millimeters. The most common width in PCs is 22 mm; length varies by application and chassis.

Common Sizes (WWLL)

• 2230 → 22 × 30 mm — Very compact; Wi‑Fi/BT, WWAN, embedded.
• 2242 → 22 × 42 mm — Compact SSDs or small form‑factor systems.
• 2260 → 22 × 60 mm — Less common; some OEM platforms.
• 2280 → 22 × 80 mm — Most consumer SSDs in desktops/laptops.
• 22110 → 22 × 110 mm — Workstation/server or high‑capacity SSDs.

Thickness & Component Sides

• Boards may be single‑sided (components on one face) or double‑sided. Chassis clearance and heatspreaders can limit supported module types.
• Exact mechanical envelopes and tolerances are defined by the official specification; always verify your system’s supported thickness.

Sockets (1/2/3) and Typical Uses

• Socket 1 — Typically wireless (Wi‑Fi/Bluetooth), often Key A/E.
• Socket 2 — WWAN or SSD (SATA/PCIe x2) on some designs.
• Socket 3 — Storage (NVMe PCIe or SATA), commonly Key M or B+M.

Mounting & Hardware

• Modules fasten via a single mounting hole at the free end. Motherboards provide standoff positions at common lengths (2230/2242/2260/2280/22110).
• Consumer boards typically use a small M2 screw with a standoff; don’t overtighten. Use the standoff location matching the module length.

Thermal Considerations

• High‑performance NVMe SSDs can throttle thermally. Heatsinks or pads are commonly recommended by vendors and motherboard makers.
• Ensure airflow and avoid obstructing thermal pads/heatsinks with cables.

RF Considerations (Wi‑Fi/WWAN)

• Wireless modules may require external antennas via miniature RF connectors (e.g., MHF4/u.FL). Confirm connector type and cable routing.

Reading Module Labels

• Size code (e.g., 2280) → width × length in mm.
• Keying and interface (e.g., “Key M, PCIe Gen3×4 NVMe” vs “SATA”) determine compatibility and performance; match to the host slot’s capabilities.

For exact dimensions, tolerances, and keep‑out zones, consult the official specification and your motherboard/device vendor documentation.

M.2 Connector Pinout (75 Positions)

The M.2 connector has 75 positions, with pins on both the top and bottom edges. Pin numbering is from 1 to 75. Not all pins are used by all modules; the specific pins used depend on the module's keying and the interfaces it implements.

The following table provides a general overview. Refer to specific device or motherboard documentation for precise implementations. Signals are often differential pairs (e.g., PETp0/PETn0 for PCIe Transmit Pair 0).

Note: Pin functions can vary depending on the specific M.2 module type and the host system's implementation. "Notched" indicates pins removed for a specific key.

Configuration Pins (CONFIG_0-CONFIG_4)

Pins CONFIG_0, CONFIG_1, CONFIG_2, CONFIG_3, and CONFIG_4 are used by the M.2 module to indicate its presence and supported functionalities to the host system. The host reads the state of these pins (grounded by the module or left open) to determine how to interface with the card. The exact interpretation varies by module type (SSD, WWAN, Wi-Fi).

References & Further Reading

• Primary Source: M.2 (NGFF) Connector Pinout at PinoutGuide.com
• PCI-SIG
• Wikipedia: M.2 on Wikipedia

This page provides a general overview. Always consult the official datasheets for your specific M.2 card and host device for precise pinout information and compatibility. Pin functionalities can vary significantly based on the device and its intended application.