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Authoritative answers: USB Type-C/PD FAQ (Part 3)

Latest update time:2021-09-03 15:47
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Authoritative answers: USB Type-C/PD FAQ Let's continue! After launching Authoritative answers: USB Type-C/PD FAQ (Part 2) last time , do you have a comprehensive understanding of Cypress EZ-PD CCGx products? Next, we will give you a more in-depth introduction to USB Type-C cables and EMCA to help you solve more practical problems in design and application!



What is EMCA? When should I use EMCA?


EMCA stands for Electronically Marked Cable Assembly. EMCA integrates electronic devices to provide a method to determine the characteristics of the cable, such as current carrying capacity, performance, and supplier identification (USB Type-C cable ID function).


The USB Type-C cable (or USB Type-C controller) needs to be electronically marked when :

• USB Type-C cable current needs to be more than 3A

• For a USB Type-C cable to be a full-featured cable, it requires USB 3.1 Gen1 or USB 3.1 Gen2 signaling

What does VCONN_SWAP mean? When should I use it?


EMCA requires VCONN to power the tag electronics inside the cable. The VCONN_SWAP message is used to request a VCONN signal swap for the EMCA cable. In addition, VCONN_SWAP may also be sent by the Port Partner. Once the host and device have established a connection through the USB Type-C port, if the CC1 or CC2 signals in the host USB Type-C receptacle are not used for CC communication, they will be re-adjusted to VCONN.


At the same time, the host can power the cable and accessories through the VCONN pin. First, the DFP downstream port with USB-PD communication function detects the EMCA cable and enables power to VCONN. When the battery on the DFP side is discharged to the state where it cannot send a signal to VCONN, the DFP will start VCONN_SWAP .

What data can Type-C cables transmit?


A full-featured USB Type-C cable can transmit USB 2.0, USB 3.1 Gen1, and USB 3.1 Gen2 data in standard mode. A full-featured USB Type-C cable can also transmit alternate mode data (such as DisplayPort, HDMI, and Thunderbolt 3) when the port enters alternate mode .

What is the maximum power that a Type-C cable can carry?


The power of a USB Type-C cable is determined by its current carrying capacity. USB Type-C cables can carry up to 5A of current, and only EMCA cables can support more than 3A of current.

Can a Type-C cable be designed that can carry higher power than the Type-C and PD specifications?


Yes. However, it is up to the designer to determine if such non-standard designs are qualified . The USB Type-C connector is capable of carrying up to 100 W (20 V, 5 A). Therefore, USB Type-C and USB-PD standard cables can only carry up to 100 W (20 V, 5 A). The USB-IF organization has not developed a specification for power transmission above 20 V or 5 A for USB Type-C ports, so it is not recommended.

How many EZ-PD™ CCG2 USB Type-C controllers are required for a USB Type-C cable?


USB Type-C passive cables require an IC with an electronic marker on one end of the cable. USB Type-C active cables with different capabilities on each end of the cable require an IC with an electronic marker on each end of the cable. The downstream facing port (DFP) will issue a cable query to learn what capabilities are supported on each end of the cable.


For more details, see AN95615 - USB 3.1 Type-C Cable Design Using EZ-PD™ CCG2.

Does CCGx support cable compensation?


Yes. CCGx can support cable compensation by requesting a higher voltage than the device requires to help compensate for the IR drop in the cable.

How many external components can be reduced by converting a CCG1 Type-C controller to a CCG2 Type-C controller that supports Type-C cable applications?


In the single-chip EZ-PD CCG1 based cable solution, we need 11 resistors, 5 capacitors, 2 diodes, and 2 FETs, while in the single-chip EZ-PDCCG2 based cable design, we only need 1 resistor and 4 capacitors.


In a two-chip EZ-PD CCG1 based cable solution (one chip per Type-C plug), we need 22 resistors, 10 capacitors, and 4 FETs, while for a two-chip EZ-PD CCG2 based cable design, we only need 2 resistors and 6 capacitors. See the table below for more details.

Single core wire

External Components

EZ-PD™ CCG1

EZ-PD™ CCG2

Save material costs

Resistor

11

1

10

Capacitors

5

4

1

diode

2

0

2

FET

2

0

2

total

20

5

15

Two-core wire

External Components

EZ-PD™ CCG1

EZ-PD™ CCG2

Save material costs

Resistor

22

2

20

Capacitors

10

6

4

FET

4

0

4

total

36

8

28

For Type-C cable design using CCG2, refer to application note AN95615 - Designing USB 3.1 Type-C Cables Using EZ-PD™ CCG2.

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