Previously, we had many conventional interpretations around the type-c interface. This time, we will delve deeper into the type-c technical parameters and conduct a more in-depth analysis of this interface.

1、 USB PD communication instructions

USB Power Delivery (USB PD) is a protocol specification that supports up to 100W power transmission and data communication simultaneously in a single cable. USB type-c is a brand new forward and backward USB connector specification that can support a series of new standards such as USB 3.1 (Gen1 and Gen2), Display Port, and USB PD. The USB type-c port can support up to 5V3A by default. If a USB PD is implemented in the USB type-c port, it can support the 100W power (5V20A) defined in the USB PD specification. Therefore, having a USB type-c port does not mean it supports USB PD.

USB PD may seem like just a protocol for power transmission and management, but in reality, it can change the port role, communicate with active cables, and allow DFP to become a receiving device. Therefore, devices that support PD generally need to use CC Logic chips.

2、 USB type-c VBUS current detection and usage

The USB type-c has added current detection and usage functions, with three new current modes: the default USB power mode (500mA/900mA), 1.5A, and 3.0A. The three current modes are transmitted and detected by CC pins. For DFPs that need broadcast current output capability, they need to be realized by CC Pull-up resistor Rp with different values; For UFP, it is necessary to detect the voltage value on the CC pin to obtain the current output capability of the other DFP.

USB 3.0 cable, straight type-c/straight A-type

3、 DFP to UFP and VBUS management and detection

DFP is a USB type-c port on the host or hub, connected to the device. UFP is a USB type-c port on the device or hub, connected to the host or hub's DFP. DRP is a USB type-c port that can work as both DFP and UFP. DRP switches between DFP and UFP every 50ms in standby mode. When switching to DFP, there must be a resistor Rp pulled up to VBUS or an output current source on the CC pin. When switching to UFP, there must be a resistor Rd pulled down to GND on the CC pin.

4、 DRP concept, DFP concept, UFP concept

The data transmission mainly consists of two sets of differential signals, TX/RX, and CC1 and CC2 are two key pins, which have many functions: detecting connections, distinguishing between front and back, distinguishing between DFP and UFP, that is, master-slave configuration Vbus, with two modes: USB type-c and USB Power Delivery. Configure Vconn. When there is a chip in the cable, one cc transmits the signal and the other cc becomes the power supply Vconn. Configure other modes, such as when connecting to audio accessories, there are 4 power and ground options for dp and pcie, which is why it can support up to 100W.

DRP (Dual Role Port): A dual role port that can be used as both DFP (Host) and UFP (Device), and can dynamically switch between DFP and UFP. A typical DRP device is a computer (which can serve as a USB host or a charged device), an OTG capable mobile phone (which can serve as a device for charging and reading data, as well as a host to provide power or read USB data for other devices), and a mobile power supply (which can be discharged and charged through a USB type-c port, that is, this port can discharge or charge)

5、 CCpin concept

CC (Configuration Channel): Configuration channel, which is a key channel added in USB type-c. Its functions include detecting USB connections, detecting forward and backward insertion, establishing and managing connections between USB devices and VBUS.

The CC pin of the DFP has a Pull-up resistor Rp, and the UFP has a pull-down resistance Rd. When not connected, DFP's VBUS has no output. After connection, the CC pin is connected, and the CC pin of DFP will detect the pull-down resistance Rd of UFP, indicating that it is connected. DFP will turn on the Vbus power switch and output power to UFP. If the value of Rp is different, the voltage detected by CC pin will be different, and then the DFP terminal will be controlled to execute which power supply mode.

Source: Ding Ning Lectures on Entertainment