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What is the Definition of Resistance and Capacitance in Type-C Connector


As Type C was first introduced, there was a widely reported incident known as the “Benson Leung saga.” Google engineer Benson Leung destroyed his $800 Chromebook Pixel laptop by incorrectly connecting a USB Type-C cable. With more and more Type C connector manufacturers entering the market and competition becoming increasingly fierce, various connectors that do not meet protocol standards are being shipped, leading to numerous quality risks. Today, we will discuss the selection of resistors and capacitors in the Type C connector, starting with pin definitions.

20 Pins info of USB-TypeC, more info check this https://www.usb.org

The pin definitions for 16-pin USB-TypeC are as follows:

While the 24-pin full-featured TypeC connector is functional, its procurement cost is relatively high. Additionally, many small household appliances do not require USB 3.0, and USB 2.0 is sufficient for general device use, which led to the creation of the 16-pin TypeC connector.

The pin definitions for 16-pin USB-TypeC are as follows:

While the 24-pin full-featured TypeC connector is functional, its procurement cost is relatively high. Additionally, many small household appliances do not require USB 3.0, and USB 2.0 is sufficient for general device use, which led to the creation of the 16-pin TypeC connector.

The pin definitions for 12-pin USB-TypeC are as follows:
The 16-pin is the official name for the connector as packaged by manufacturers, but it is commonly referred to as the 12-pin in daily life. This is because, during interface design, the two Vbus and GND output wires at both ends of the TypeC female connector were combined, resulting in 16 output wires, but only 12 solder pads were needed for the connection.

What are pull-up and pull-down resistors in the protocol?

Resistors play a role in limiting current in a circuit. Pull-up and pull-down resistors are commonly used in system design. Simply put, a resistor connected from a power source to a device pin is called a pull-up resistor, which normally keeps the pin at a high level. A resistor connected from the ground to a device pin is called a pull-down resistor, which normally keeps the pin at a low level. In an IC, a low level is connected to GND, while a high level is connected to a high resistance. Pull-up resistors “pull” an uncertain signal to a high level through a resistor and also limit the current, while pull-down resistors do the same for a low level. For non-collector (or drain) open-circuit output circuits (such as ordinary gate circuits), their ability to raise current and voltage is limited, and the main function of pull-up and pull-down resistors is to provide an output current channel for the collector open-circuit output circuit. Pull-up injects current into the device, while pull-down outputs current; the strength only differs based on the different resistance values of the pull-up or pull-down resistors, and there is no strict differentiation. When an IC’s I/O port node is at a high level, the impedance between the node and GND is very high, almost infinite, and the voltage drop across the pull-up resistor (such as a 4.7k ohm or 10k ohm resistor) can be neglected. When the I/O port node needs to be at a low level, just connect it to GND, and VCC and GND are connected through the pull-up resistor (such as a 4.7k ohm or 10k ohm resistor) with a very small current passing through, which can be neglected.

A brief summary of the functions of pull-up and pull-down resistors are as follows:

  1. To increase voltage levels

When a TTL circuit drives a CMOS circuit, if the high level output of the TTL circuit is lower than the lowest high level of the CMOS circuit, a pull-up resistor should be connected to the output of the TTL circuit to increase the value of the output high level. An OC gate circuit must be connected to a pull-up resistor to increase the high-level value of the output.

  1. To increase the driving capability of output pins

Pull-up resistors are also commonly used on some microcontroller pins.

  1. To prevent electrostatic discharge and interference on unconnected pins (N/A pins)

In CMOS chips, unconnected pins cannot be left floating to prevent damage from electrostatic discharge. A pull-up resistor is typically added to reduce input impedance and provide discharge channels. Leaving pins floating is more likely to receive electromagnetic interference from the outside world.

  1. For resistor matching

Adding pull-up and pull-down resistors to match the resistance can effectively suppress reflection wave interference in long-line transmission, as mismatched resistance can easily cause reflection wave interference.

  1. For preset space status/default potential

Some CMOS input terminals are connected to pull-up or pull-down resistors to set the default potential. When these pins are not used, these input terminals are pulled down to a low level or pulled up to a high level. The idle state of I2C and other buses is obtained by pull-up and pull-down resistors.

  1. To improve the noise margin of chip input signals

If the input terminal is in a high impedance state or the high-impedance input terminal is left floating, a pull-up or pull-down resistor should be added to avoid the influence of random levels and affect the circuit operation. Similarly, if the output terminal is in a passive state, a pull-up or pull-down resistor should be added to improve the noise margin of the chip input signal and enhance anti-interference capability.

How associations define the use of related resistors

Most people first became familiar with fast charging through Qualcomm’s QC technology, which increases the transmission power by increasing the transmission voltage. However, in the QC protocol, USB DP and DM are used for communication, which can affect USB communication during charging. The USB-PD protocol relies on CC1 and CC2 pins for power device identification, avoiding conflicts between QC standards and DP and DM. This ensures that data transmission is not affected while transmitting power through USB-PD. Since USB-PD’s power transmission is closely related to CC1 and CC2 pins, small appliances without built-in PD protocol chips need to configure Ra/Rd pull-down resistors on CC1 and CC2 pins to draw power from the USB-PD power supply. Without pull-down resistors, power reception can be affected.

There are two most common current modes for Type-C, 1.5A and 3A, which mainly depend on the output capability of the DFP. The DFP informs the UFP of its power supply capability via the voltage on the CC pin. If the UFP’s pull-down resistor Rd=5.1K, the DFP can generate voltage on the CC pin through its pull-up resistor or current source. Need a USB-C quote, please click https://www.dbtlink.com/contact-us/
The Type-C protocol specification provides specifications for the pull-up resistor or current source under different output modes. Simply put, a 56K resistor means that the default current for USB 3.0 is 5V and around 900mA, while a 10K resistor means that the default output is 5V and 3A. If you use a 10K resistor for a low-current device, it will be mercilessly penetrated. Currently, most of these resistors are used in USB-A to USB-C adapter cables. For example, if your phone has a USB-C interface and you connect it to a laptop’s USB-A port for charging via this cable, the 56k resistor tells the phone that it is a traditional USB interface and negotiation must be done according to the protocol to determine the output current, especially for traditional USB interfaces that can only output 500mA of current. After negotiation, the phone will be charged according to the output capability of the USB host interface. If this resistor is incorrect or some bad cables are used, it may use a 3A current and tell the phone to obtain 3A current from the host, which can cause significant impact on the USB-A side. Will it burn or catch fire? It depends on the design of the host side, so reasonable capacitors added to the USB Type-C circuit can stabilize the circuit and prevent the main chip from being penetrated by high current.

As shown in the pin definition diagram above, we know that regardless of the number of PINs, there are two CC pins in a Type-C cable. If one of them is used to identify the DFP and UFP, then the other can be used as VCONN to provide power for active cables. When the DFP detects, with a maximum power of 1W. Accurate power consumption, multi-function signals, and robust design are key considerations for choosing USB Type-C accessories; poorly designed USB Type-C cables, connectors, and other accessories can cause permanent damage to the hardware they serve. Therefore, it is essential to have Type-C cables (with Type-C connectors on both ends) that meet strict quality standards.

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