USB-C and USB-C PD (Power Delivery) support higher voltage and power levels. It is a reversible connector, and the pin spacing is closer than that of USB Micro-B, which increases the risk of short circuits. In addition, as portable electronic devices become more complex, more advanced protection against ESD, surge, and overvoltage is required. This article explains how to significantly reduce BOM and PCB area by using a compact protection IC with comprehensive functions.

■ Improved convenience of USB Type-C electronic device connection and power supply

The introduction of new USB Type-C (USB-C) cables and connectors has greatly improved the convenience of connecting and powering electronic devices such as digital cameras and ultra-thin tablets (Figure 1). USB-C can charge up to 15W, and USB-C PD can charge up to 100W, enabling charging between a wider variety of devices. However, USB Type-C poses new challenges for system protection. This new connector has a tighter pin pitch than USB Micro-B, which increases the risk of short-circuiting when connected to VBUS. It also supports higher voltages with USB PD, requiring more robust protection. Ultimately, as electronic loads become more complex, more advanced protection against ESD and voltage surges is required. This article describes the USB Type-C PD architecture, examines the challenges associated with protecting the D+/D- data signals, and explains how these challenges can be addressed with minimal BOM and PCB area using a highly integrated 2 x SPDT switch.

■ USB-C PD system

Figure 2 shows a typical portable power management system connected with a USB-C cable and powered by a lithium-ion (Li+) battery. When VBUS is available, power is supplied to the charger, the system, and the remaining blocks. In this case, the battery is charged. When VBUS is not available, the battery supplies power to the system. The USB-C cable has CC1 and CC2 pins that are responsible for port connection, cable orientation, role, and port control. The D+/D- lines are standard USB-C communication lines, handling data at a rate of 480 Mbps and protected using the D+/D- protection device. The PD controller is responsible for the PD protocol.

■ Challenges related to protection functions

Electrical surges and electrostatic discharge (ESD) are prevalent in power supply equipment and can cause interference with each other or damage electronic loads and equipment. ESD is caused by the transfer of electrostatic charge from the human body to electronic circuits and is a critical issue in portable electronics. Surges can be caused by lightning or can be induced by long cables running near a lightning strike. Surges can also occur when switches or relays are turned on and off. Load dump is a surge that occurs when the battery is disconnected in an automobile. A good data line protection IC must provide adequate protection without interfering with data transmission.

■ Highly integrated solution

The MAX20334 is a 2 x SPDT switch that is ideal for overvoltage protection in portable electronics (Figure 3). The IC can be used to protect downstream data lines from high-voltage shorts, ESD, and surge events. The MAX20334 features low on-capacitance and low on-resistance, which are important characteristics for high-performance switching applications in portable devices. The IC also includes protection against positive overvoltage and surge. It supports USB low/full/high-speed signaling, operates on 2.7 V to 5.5 V power supply, is available in a 12-bump (1.23 mm x 1.63 mm) wafer-level package (WLP), and operates over an extended temperature range of -40 °C to +85 °C.

■ Provides comprehensive protection functions

All pins of this IC include ESD protection structure, providing ESD protection up to 2kV (human body model) during handling and assembly. Furthermore, COMA and COMB (Figure 2 and Figure 3) provide protection against higher ESD up to ±15kV (human body model), ±15kV (air gap discharge technique defined by IEC 61000-4-2), and ±8kV (contact discharge technique defined by IEC61000-4-2). This ESD structure can withstand high levels of ESD both during normal operation and when the device is powered down. Even if an ESD event occurs, this IC will not latch-up and will continue to operate. This IC also protects against surges from -30V to +45V (IEC61000-4-5) and overvoltages up to +20.5V.

Figure 4 shows a comparison of the PCB layout when using this IC with a competitive device that only protects against positive surges and has lower overvoltage (OV) and ESD protection levels. The latter requires additional circuitry to meet ESD/surge/OV requirements, increasing BOM cost and taking up five times more PCB area.

■ Data Integrity

The eye diagram in Figure 5 shows that the integrity of the data signal is excellent. The round blue line is kept as far away from the unacceptable red area as possible. The high bandwidth of this protection IC ensures that there is minimal delay and jitter in the signal rise and fall times, which provides a significant margin for error. This is important for passing USB compliance tests.

■ Need for improved protection against ESD and voltage surges

USB Type-C brings new challenges to connecting, powering, and protecting electronic devices such as digital cameras and ultra-thin tablets. The new connector has a tighter pin pitch than USB Micro-B, which increases the risk of short circuits when connected to VBUS. In addition, USB PD requires more robust protection as the voltage increases. In addition, as electronic loads become more complex, improved protection against ESD and voltage surges is required. This article shows how an integrated protection device featuring 15kV ESD protection, -30V to +45V surge protection, and +20.5V overvoltage protection can protect data lines and meet ESD/surge/OV requirements with a smaller BOM and smaller PCB area than less integrated devices.

※ About the author
Nazzareno (Reno) Rossetti is an analog and power management expert at Analog Devices. He is an author of several patents in this field. He holds a Ph.D. in electrical engineering from the Polytechnic University of Turin, Italy.

Josh Frankhauser is a manager in the Industrial and Healthcare business unit at Analog Devices, where he focuses on industrial communications solutions. He holds a Masters degree in Materials Engineering from UCLA.