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Logic principle and necessity of TYPEC interface chip CC

信息来源:Olink Technology丨Computer Cable Assembly丨Game machine Cable assembly丨USB cable丨Mobile data cable  时间:

Does my TYPEC interface device really need a TYPEC interface to control the chip?

Driven by strong USB type-C by virtue of its powerful function, in the Intel,  Google and other manufacturers will quickly lead to a revolution in the USB interface, and the positive impact on our daily life. In order to be able to make their own equipment is compatible with these interfaces, often need to increase a TYPEC interface CC logic control chip, but in fact and not every kind of devices are need to increase the CC logic control chip (for example: legendary technology LDR6013). This paper discusses a major problem: USB Type-C equipment whether they need CC logic detection and control chip?

To answer this question, we have to start with the basic concepts.

DFP (Downstream Facing Port):

Down port, can be understood as DFP, VBUS provides Host, you can also provide data. A typical DFP device is a power adapter because it is always provided with a power supply.

UFP (Upstream Facing Port): upstream port, can be understood as Device UFP, to take power from the VBUS, and can provide data. Typical device is a U disk, mobile hard disk, because they are always read data and power from the VBUS, of course, does not rule out the future may arise as a host of U disk.

DRP (dual role port): dual role port and DRP both can do DFP (host), may also make the UFP (device), can also be used in dynamic switching between DFP and UFP. Typical of the DRP equipment is computer  equipment, with OTG function of the mobile phone can be as the equipment is charged and read data can also be as a host for other devices provided power source or read U disk data), mobile power (charge and discharge through a USB type-C, namely the mouth can discharge can also be charged).

CC (configuration channel: channel configuration, which is the key channel USB type-C added. It has a USB connection detection, detection of positive and negative in that USB device data and VBUS connection establishment and management etc..

A communication protocol of USB PD (USB power delivery):PD, it is a new power supply and communication link, which allows USB devices transmission to a maximum of 100W (20V/5A) power and it can change the port attribute can also switch the port between DFP and UFP, it can and communication cables and cable access attributes.

Electronically marked cable, the: encapsulation E-Marker chip USB type-C active power cable, DFP and UFP using PD protocol can be read by the properties of the cable: power transmission capability and data transmission capabilities, ID, and other information. All the functions of the Type-C cable should be encapsulated with E-Marker, but USB2.0 Type-C can not cable package E-Marker.

USB Type-C DFP-to-UFP equipment configuration process and VBUS management has the following main process:

Equipment connection and the separation of detection: DFP need to detect CC tube feet with a voltage to determine the UFP device has been plugged or unplugged to provide and manage VBUS. when no UFP device is plugged in, you must close the VBUS, which is different from most existing power adapter. So all the DFP devices need CC logic detection and control chip as well as VBUS switching circuit.

The insertion direction detection: as shown in Figure 1, although the USB type-C socket and plug the two rows of tube feet under symmetric, USB data signal have two groups of repeated passages. However, as the main control chip usually only a group of TX / RX and D+/- channel. Due to the USB2.0 data the highest rate of only 480mbps, can not consider signal line impedance continuity and get better quality of data transmission, therefore USB2.0 D+/- signal can not MUX control directly from the main control chip a second connection to the USB type-C socket D+/- pin But the data of USB 3.0 or usb3.1 up to 5Gbps or 10Gbps rate. If the signal line or be simply divided into two words, discontinuous signal line impedance will seriously damage the quality of data transmission. Therefore, it is necessary to the MUX switching to ensure the consistency of the impedance signal path in order to ensure the quality of signal transmission. As shown in the figure shown on the right side of the MUX from TX1/RX1 TX2/RX2 choose a road connection to the main control chip, and the MUX is must be controlled by the CC logic.

 

Therefore, in the USB2.0 application, there is no need to consider the direction detection problem, but the USB3.0 or USB3.1 application, we must consider the direction detection problem.


 

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Figure 1 USB Type-C data line logic model

 

A situation can not MUX in the application of USB3.0/USB3.1 but must pay attention to the, that do not need to detect the direction, as shown in Figure 2, whether it is in or in, the left side of the host are can according to CC tube feet to switch the MUX connectivity to USB3.0/USB3.1 signal. This scene occurs in the right side of the device is always the case of UFP, such as U disk, mobile hard disk, etc..

Therefore, USB3.0/USB3.1 applications, in addition to all devices outside of the UFP device are required CC logic detection and control chip.

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Establishment of DFP-to-UFP and VBUS management and detection

DRP switch between and DFP at 50ms and UFP in standby mode. When the switch to the DFP and CC tube feet must have a pull to VBUS resistance RP or output a current source, when the switch to the UFP CC pipes feet must have a drop-down to GND resistance Rd. the switch action must be done by the CC logic chip LDR6013.

When the DFP detected UFP insertion can output VBUS. When UFP pulled out after must close VBUS. this action must to be completed by the CC logic chip.

With the use of USB Type-C detection VBUS current

USB type-C added the current detection and use function, the new current mode: the default USB power supply mode 500mA/900mA, 1.5A and 3.0A. current mode CC tube feet to transmit and detect, for broadcast current output capacity of the DFP and need the different value of the CC pull resistance RP to achieve; for the UFP and need to detect CC tube feet on the voltage value to obtain the current output capacity of the other DFP.

USB PD communication

The seemingly just power transmission and management agreement, in fact it can be to change the role Port USB PD, and active communication cable, allowing DFP become subject to the electric equipment, and many other advanced features and, therefore, support equipment for the PD must adopt CC logic chip.

Discovery and configuration to extend other peripherals (Audio, Debug)

USB type-C voice attachment and debug mode support, USB type-C interface headset if only as UFP and because of less power consumption without detection of DFP supply capacity, no need to CC logic chip. The