PCB Layout Guidelines for USB Type-C

Introduction to USB Type-C

USB Type-C (USB-C) is a universal connection standard used for device connectivity and charging. As the latest evolution of USB interface, USB-C comes with several advantages, including reversible plug orientation, higher data transfer rates, and power output capabilities. Additionally, USB Type-C can transmit audio and video signals and is compatible with various accessories such as monitors, external storage devices, and chargers.

Features of USB Type-C

Reversible Plug Orientation: Unlike traditional USB interfaces, USB Type-C can be inserted in any orientation without worrying about the direction.

High-Speed Data Transfer: USB Type-C supports higher data transfer rates, reaching the speeds of USB 3.1 and Thunderbolt 3, enabling fast file transfers and video playback.

Power Output: USB Type-C supports higher power output, capable of charging devices such as laptops, tablets, and other high-power devices.

Versatility: USB Type-C can transmit audio and video signals, and it supports various accessories like monitors, external storage devices, and chargers.

Signal icon

The USB Type-C connector has 24 pins. The two images below show the pins of the USB Type-C receptacle and plug, respectively.

The picture from Microship

PCB Design Requirements for USB Type-C Interface

Layout USB Type-C Design:

● ESD and common-mode inductor components should be placed near the Type C interface in the following order: ESD → common-mode inductor → capacitor. Maintain a certain distance from Type C to account for post-soldering situations.

● Coupling capacitors for TX signal lines should be placed near the interface, while coupling capacitors for RX signal lines are provided at the device end.

● Voltage regulators should also be placed as close to the connector as possible.

Routing Design:

To prevent signal interference, it is recommended to keep high-speed USB differential lines and digital signal lines away from traces, minimize the use of vias and corners on high-speed USB signal lines, maintain impedance control, and prevent signal reflection.

Prohibit the use of 90° routing corners; instead, use two 45° corners or arcs to reduce signal reflection and impedance discontinuity.

Avoid placing signal lines under crystal oscillators, crystals, clock synthesizers, magnetic devices, and clock multiplier ICs. Avoid using short stubs, and if necessary, make sure they are not longer than 200 mils.

Route high-speed signal lines on the same layer whenever possible. Ensure that the trace's return path has a complete, unsegmented mirrored plane, preferably selecting the GND plane. Avoid traces crossing over mirrored plane segmentation lines to reduce inductance and signal radiation.

CC1 and CC2 are two crucial pins with multiple functions, including cable connection and removal detection, socket/plug orientation detection, and current broadcasting. Bold routing is required when routing these pins.

The following diagram illustrates how CC1 and CC2 pins indicate socket/plug orientation. In this diagram, DFP represents Downstream Facing Port, which serves as the host or power source in data transmission. UFP represents Upstream Facing Port, which is connected to the host or power consumer device.

Differential Signal Routing:

The impedance control of Type C differential traces is 90 ohms ±10%. It is essential to maintain impedance continuity, ensure a good reference plane without crossing segmentation, and limit the number of signal via layer changes to no more than 2.

Shorten the length of high-speed USB signal lines that run parallel to high-speed clock lines and AC signal lines, or increase the spacing between them to minimize crosstalk.

Ensure that the spacing between differential signal lines and other signal traces is at least 50 mils. Adopt a tightly coupled mode and determine the specific trace spacing and width through software calculation.

Maintain consistent spacing and length matching for differential signals, with a maximum length difference of 200 mils.

CC1 and CC2 are two crucial pins with multiple functions, including cable connection and removal detection, socket/plug orientation detection, and current broadcasting. Bold routing is required when routing these pins.