An e-marker (Electronically Marked Cable) is a small embedded chip within certain USB-C cables that communicates the cable's capabilities to connected devices. Here's a detailed breakdown:

Key Functions:

1. Power Delivery (PD) Negotiation:

Specifies maximum voltage (e.g., 20V) and current (e.g., 5A), enabling high-power charging (up to 100W).

Prevents devices from exceeding the cable’s limits, ensuring safety and compatibility.

2. Data Transfer Specifications:

Indicates supported data protocols (USB 3.1, USB4, Thunderbolt 3/4) and speeds (up to 40 Gbps).

Ensures optimal performance for high-speed data or video output.

3. Cable Identification:

Store details like manufacturer, certification status (USB-IF), and cable length.

Helps devices verify authenticity and compliance with standards.

Technical Context:

Configuration Channel (CC): Uses the USB-C CC pin to exchange information with devices.

Mandatory for High-Spec Cables: Cables supporting >60W (3A) or USB 3.1+/Thunderbolt are required.

Safety: Prevents overheating by limiting power if the cable lacks an e-marker or is non-compliant.

Examples:

A 100W USB-C cable includes an e-marker to confirm it can handle 5A.

Thunderbolt 4 cables use e-markers to enable 40 Gbps speeds and daisy-chaining.

Importance:

Avoids Compatibility Issues: Ensures devices operate within the cable’s rated specs.

User Awareness: Cheap cables without e-markers may fail to support fast charging or data.

Tag：e-marker,USB-C