USB interface current refers to the current flow through the USB interface. This current is used for data transmission and for powering connected devices. Different USB interface standards and device types may have different current requirements.

Standard USB current:

For USB 2.0 interfaces, the standard maximum current is usually 500 milliamps (mA).

USB 3.0 interfaces support higher currents, typically up to 900mA, to support higher data speeds and greater power demands.

Charging current:

When the USB interface is used for charging, the current size depends on the charging protocol and device requirements.

Normal USB Charging typically follows the USB Battery Charging Specification(USB-BCS), which defines different charging port types (e.g., Standard downstream port SDP, charging downstream port CDP, dedicated charging port DCP), each of which supports different current outputs.

Fast charging technologies (such as USB-C Power Delivery, Qualcomm Quick Charge, etc.) support higher currents to achieve faster charging speeds.

Safety restrictions:

Both USB interfaces and cables have current carrying capacity limits, exceeding these limits may result in device damage or safety hazards.

Therefore, it is very important to use chargers and cables that meet the specifications.

Equipment requirements:

Different USB devices have different requirements for current. For example, some high-power devices, such as external hard drives, may require higher currents to function properly.

In general, the USB interface current refers to the electrical flow provided to the connected device through the USB interface, and the size of this current depends on several factors such as the interface standard, device requirements and charging protocol. When using USB devices, ensuring that the current meets the requirements is the key to ensuring the normal operation and safety of the device.