“The USB Type-C interface is more and more widely used in consumer products because of its miniaturization, reversible insertion, support for high power, high-speed data transmission and other characteristics.
The USB Type-C interface is more and more widely used in consumer products because of its miniaturization, reversible insertion, support for high power, high-speed data transmission and other characteristics.
Type-C has strong compatibility. In addition to retaining the D+/D- pins to support USB 2.0 data transmission, it is also compatible with signal transmission of other protocol standards in the specification definition, such as support for DP signal transmission. Therefore, it has become a standardized interface that can be widely connected to most Electronic devices such as smartphones, PCs, game consoles, storage devices and docking stations, realizing the unification of data transmission and device charging.
The current mainstream USB Power Delivery 3.0 can support a high power output of 20V/5A, that is, a charging power of 100W (PD 3.1 released in May 2021 further supports power specifications up to 48V/5A). In addition to high-power charging based on the PD specification, the USB Type-C interface can also implement DisplayPort 1.4 video transmission, Thunderbolt 4 and other functions. Therefore, a device with a full-featured Type-C interface can realize functions such as bidirectional charging and video output through a single interface.
Figure 1 USB Type-C interface pinout
The USB Type-C connector has a small size and realizes 24 connector pins in a space of 8.3 x 2.5mm. It has a high pin density and needs to meet tens of thousands of plug-in applications in terms of structural design.
Compared with other USB interfaces in earlier versions, the VBUS pin of Type-C is more prone to short-circuit with adjacent pins due to foreign objects or abnormal insertion and removal. Since the voltage of VBUS may be as high as 20V, a short circuit with low voltage pins (such as CC, SBU, Tx/Rx, etc.) will cause serious consequences. Secondly, the power path of the Type-C application needs to have a large current flow capacity to effectively protect against potential load short-circuit, overcurrent and other hazards. In addition, as the external interface of electronic equipment, ESD and surge damage must be paid attention to from the system level, and overvoltage caused by hot plugging and other reasons must also be considered.
In conclusion, USB Type-C is powerful, but in product development, robust design at the system level also faces many challenges.
All-round protection solution for USB Type-C interface
Well semiconductor, a subsidiary of the OmniVision Group, has launched a comprehensive solution for USB Type-C applications. On the premise of ensuring that high-power and high-speed data transmission performance is not sacrificed, it provides safe and reliable protection for interfaces, helping equipment manufacturers to effectively reduce product repair rates and improve product quality.
Figure 2 Functional block diagram of the USB Type-C interface of a laptop
The protection scheme consists of three devices (corresponding to the orange part in Figure 2), namely WS4684C-15/TR, WS4683C-16/TR and WS3233Q-20/TR.
01. WS4684C-USB power switch
In order to suppress possible high voltage surges and provide reliable protection for the charging interface, a high-performance OVP Load Switch is essential. The WS4684C-15/TR supports the 20V/5A specification of USB PD, enabling fast, high-power charging of laptops. Its VBUS and other pins can withstand 29V DC voltage continuously. And the internal integrated surge suppression circuit, the suppression capacity is up to 90V. It can effectively protect the power path of the charging interface of consumer electronic products such as notebook computers, and greatly reduce the damage to electronic products caused by power supply accidents or consumer misoperation.
• USB Type-C VBUS charging protection
Features and advantages:
• 2.5~20V input voltage range, high current 5A, meet USB PD 3.0 high power requirements
• Programmable overvoltage protection, fast response reverse current protection, overtemperature protection
• Small form factor, 1.65 x 2.67mm, CSP-15L package
Figure 3 Typical application of WS4684C
02. WS4683C-USB current limiting load switch
The Type-C interface of the laptop usually needs to work in DRP mode. For the safety of system charging and discharging, based on the safety requirements of UL62368/CB62368, the VBUS path needs to have the output overcurrent protection function.
The WS4683C-16/TR output supports 5V (the VBUS side pin of the device has a DC withstand voltage of up to 30V) and a continuous current of 3.3A. On the premise of ensuring the reliability of the chip, it supports the FRS fast start function required by USB PD 3.0. The electrostatic discharge path (IEC61000-4-2 Contact ±8KV) is also integrated inside, which reduces the additional protection devices around and saves the cost and PCB area for the manufacturer.
Figure 4 Current protection fast response
• USB Type-C VBUS discharge protection
Features and advantages:
• 400mA~3.3A programmable overcurrent protection
• Fast response reverse current protection
• Supports the FRS function required by the USB PD 3.0 protocol
• Small size, 2.05 x 2.05mm , CSP-16L package
Figure 5 Typical application of WS4683C
03. WS3233Q-USB Type-C protection switch
As mentioned above, since the small spacing between the power and signal pins of the USB Type-C interface is only 0.5mm, the VBUS will be at risk of short-circuiting with the surrounding pins due to foreign objects in actual use by the user, which is a low-voltage signal pin. and related circuits bring hidden dangers.
The overvoltage protection switch launched by Weir Semiconductor, the WS3233Q-20/TR signal path has a -3dB bandwidth of up to 800MHz, and achieves 24V overvoltage protection capability without affecting the integrity of high-speed signals. On a single chip, high voltage and high speed performance no longer compromise each other. In addition, the WS3233Q also integrates the D+D- channel ESD discharge path, which meets the IEC61000-4-2 Contact ±8KV standard. A single chip provides an integrated solution for overvoltage protection and electrostatic protection without affecting high-speed data transmission.
• USB Type-C CC/SBU protection
Features and advantages:
• OVP Short-to-VBUS: 24V
• Bandwidth 800MHz -3dB, achieving high withstand voltage and high bandwidth
• Low quiescent current, 70uA
• QFN3*3-20L general package
The combination of WS4684C-15/TR, WS4683C-16/TR and WS3233Q-20/TR realizes protection and suppression of various common interference abnormalities such as overvoltage, overcurrent, overtemperature, surge, ESD, etc. One of the USB Type-C interface protection solutions.
The three-chip protection scheme also brings great flexibility in system design, and can be used in full or in part according to the device interface function definition type to save costs.