Designing FX3™/CX3-Based USB Type-C Products - KBA218460

Version: **

 

Question:

How to design FX3/CX3-based products with USB Type-C connector?

 

Answer:

The salient features of the USB Type-C connectors are that they are reversible and they could provide power up to 100 W. i.e., the USB Type-C cable can be connected in any orientation (upside down) and that the VBUS voltage can be up to 20 V, 5 A. To achieve a reversible connection, the USB Type-C receptacle has one extra pair of all the USB data lines (SuperSpeed and Hi-Speed). The correct pair of USB data lines should be selected using a multiplexer based on the orientation in which the USB Type-C connector is inserted. The following sections describe three different types of FX3/CX3 designs with USB Type-C connectors. For more details on Type-C connectors and USB Power Delivery, see the USB Type-C specification and the USB Power Delivery specification. The following sections are applicable for FX3 and CX3 families of devices.

 

  1. FX3 Type-C Plug Design

      This Type-C plug design is suitable for standard devices (e.g., RAID dongles, flash drives) that require the VBUS voltage of 5 V and current not more than 3 A; such designs don’t require any USB-PD (Power Delivery) controller. For applications with Type-C Plug and FX3, a multiplexer is not required for selecting the correct pair of USB data lines because the USB Host can handle the right connection. The sample schematic for FX3-based USB Type-C plug design is shown in Figure 1. A pull-down resistor (Rd) of 5.1 K is required on the configuration channel (CC) line of the plug to indicate that the device is a power consumer (power sink) and requires VBUS of 5 V and not more than 3 A. No additional Power Delivery Controller or additional firmware implementation in FX3 is required when using a USB Type-C plug-based design because, by default, the Host provides 5 V, 3 A over Type-C. If the application needs other voltages/currents, then a PD controller is required. See section 3 for more details.  


    Figure 1. FX3 Type-C Plug Design Schematic

1.png  

  1. FX3 Type-C Receptacle Design

    Devices such as camera modules, docks, and monitors are designed with Type-C receptacles. They are connected to the USB Type-C Host through a Type-C cable. For applications that use the USB Type-C receptacle, a multiplexer is required to select the correct pair of USB SuperSpeed data lines to communicate with the USB Host depending on the Type-C connector orientation. To select the correct pair of USB data lines based on the orientation, logical decision-making should be implemented and given as an input to operate the multiplexer.

    The USB Type-C Specification, by default, without USB Power Delivery, supports transmitting up to 5 V, 3 A of power through VBUS. For applications that do not require more than 3 A current at 5 V, the USB Power Delivery Controller Chip is not required. For such cases, FX3 alone can be used to control the multiplexer SEL lines to select the correct pairs of USB 3.1 SuperSpeed lines. FX3 makes this implementation possible through its powerful ARM® core supported by the robust SDK. The sample schematic of the USB connections with USB Type-C receptacle and the multiplexer is shown in Figure 2. For the FX3 firmware implementation to control the multiplexer, contact Cypress Technical Support.  

    Figure 2. FX3 Type-C Receptacle Design Schematic

2.png


As shown in the Figure 2, the two pairs of each USB data line from the USB Type-C receptacle is connected to the multiplexer. From the multiplexer, a single pair of USB data lines is connected to FX3. The MUXSEL line is controlled through an output GPIO of FX3 to select the correct pair of USB SuperSpeed lines. The logic of selecting the correct pair of USB SuperSpeed lines is implemented in FX3 firmware.

  1. FX3 Type-C Receptacle Design with PD Controller

      For applications that require different voltages/currents other than 5 V, 3 A, a USB Power Delivery (PD) controller is necessary to negotiate the power numbers with the Type-C PD Host. The PD controller chip controls the multiplexer and selects the correct pair of USB SuperSpeed data lines. No firmware implementation is required on the FX3 side as the PD controller takes care of the USB Type-C- and PD-related requests. A reference schematic using Cypress’s EZ-PD™ CCG2 controller chip with FX3 is attached with this article. For FW, contact Cypress Technical Support.