“The USB Type-C (USB-C) cable and connector specification greatly simplifies how to interconnect and power electronics such as digital cameras and ultra-thin tablets (Figure 1). The specification supports USB-C charging applications up to 15W, while USB-C Power Delivery (PD) extends charging capabilities to 100W, including a variety of interchangeably charged devices. USB Type-C brings new challenges in system protection. The new connector has a smaller pitch than USB Micro-B, increasing the risk of a mechanical short to VBUS.
The USB Type-C (USB-C) cable and connector specification greatly simplifies how to interconnect and power electronics such as digital cameras and ultra-thin tablets (Figure 1). The specification supports USB-C charging applications up to 15W, while USB-C Power Delivery (PD) extends charging capabilities to 100W, including a variety of interchangeably charged devices. USB Type-C brings new challenges in system protection. The new connector has a smaller pitch than USB Micro-B, increasing the risk of a mechanical short to VBUS. Also, since USB PD has high voltage, stronger protection is required. Finally, Electronic loads are becoming more complex and require enhanced ESD and voltage surge protection. This design solution first explores the USB Type-C PD architecture and the challenges associated with D+/D- data signal protection, and then proposes a highly integrated 2xSPDT switch that requires less BOM and PCB footprint. Overcome these challenges.
Figure 1. Digital camera connected to tablet via USB-C cable
USB-C PD system
Figure 2 shows the front end of a typical portable power management device that connects to a USB-C cable and is powered by a lithium-ion (Li+) battery. When VBUS is present, it powers the charger, the system, and the rest of the modules, while charging the battery. When VBUS is disconnected, the battery powers the system. When using a USB-C cable, the CC1 and CC2 pins determine port connection, cable orientation, role detection, and port control. D+/D- lines are standard USB-C communication lines that process data at 480Mbps and are protected by D+/D- protectors. The PD controller implements the power supply protocol.
Figure 2. USB PD Power Management System
Power surges and electrostatic discharge (ESD) are common in power supplies and can interfere with or cause damage to electronic loads and equipment. ESD is caused by the transfer of static charge from the human body to electronic circuits, and it is a big problem for handheld electronic devices. Surges can be caused by lightning or in long cables running near the lightning strike. Switches or relays can cause surges during opening and closing operations. A load dump is a surge created by disconnecting the battery on a car. A good data line protection IC should provide adequate protection without significantly degrading data quality.
The MAX20334 is a 2xSPDT switch with overvoltage protection for portable equipment (Figure 3). The IC is designed to protect downstream data lines from high-voltage short-circuit, ESD, or surge events. The device features the low on-capacitance and low on-resistance required for high-performance switching applications in portable electronics. The IC has internal positive overvoltage and surge protection, handles USB low/full/high speed signals, and operates from a 2.7V to 5.5V supply. The IC is available in a 12-pin (1.23mm x 1.63mm) wafer-level package (WLP) and operates over the extended -40°C to +85°C temperature range.
Figure 3. 2xSPDT switch with extended protection
All pins are ESD protected to protect against electrostatic discharges up to ±2kV (Human Body Model) during handling and assembly. COMA and COMB (Figures 2 and 3) are further subjected to contacts up to ±15kV (Human Body Model), ±15kV (air-gap discharge method described in IEC 61000-4-2) and ±8kV (contacts described in IEC61000-4-2) discharge method) ESD protection without causing damage. The ESD structure can withstand high ESD both during normal operation and when the device is powered off. After an ESD event, the IC continues to operate without latch-up. The IC is surge protected from -30V to +45V (IEC61000-4-5) and overvoltage protected up to +20.5V. Figure 4 compares the PCB layout of this highly integrated extended protection solution with a typical competitor offering pure surge protection with lower OV and ESD protection. The latter requires additional circuitry to meet ESD/surge/OV specifications, increases the BOM cost, and increases the PCB footprint by a factor of 5.
Figure 4. Extended Protection Benefits
It is evident from the eye diagram of Figure 5 that the curved blue line is kept close to the maximum (close-to-maximum) distance from the forbidden red forbidden area, and the data signal has good integrity. The high bandwidth of the protection IC minimizes the reduction in signal rise and fall times and jitter, resulting in good error tolerance, which is important for passing USB compliance testing.
Figure 5. D+/D- Eye Diagram
USB Type-C brings new challenges in the interconnection, power supply and protection of electronic products such as digital cameras and ultra-thin tablet PCs. The pitch of the new connector is smaller than that of USB Micro-B, which increases the risk of mechanical short circuit to VBUS . Also, since USB PD has high voltage, stronger protection is required. Finally, electronic loads are becoming more complex and require enhanced ESD and voltage surge protection. This design solution uses enhanced protection devices that provide up to ±15kV ESD protection, -30V to +45V surge protection, and +20.5V overvoltage protection to individually protect the data lines, enabling Meet ESD/Surge/OV specifications with lower BOM and smaller PCB footprint.
The Links: NL6448BC33-70G T190C-5RBA16N-3A28R4-200FH IGBTMODULE