Summary :
Electrostatic discharge (ESD) transients could threaten the I/O electronic circuits, making it difficult for designers to provide adequate protection against overvoltage. The security applied will not hinder the operation in normal conditions, and it should not reduce the data transmission rate. The options for protecting TVSD devices from ESD caused by voltage overvoltage were discussed in the paper previously. This article aims to provide an overview of the possible application examples and industrial standards and protection methods for frequently used ports for communication, including USB, HDMI, and Ethernet.
Overvoltage protection with TVS diodes
Electronic devices communicate with the world outside via communications ports. They can be a target for overvoltage events such as EDD or electrical rapid transients(EST) and surges without a suitable overvoltage protection solution in place. The protection solution should not interfere with the speed of data transmission. Simple, traditional Protection using the capacitor is not feasible since the lines’ capacitance needs to be kept low because of the high frequencies.
DATA TRANSMISSION RATES
The International Electro-technical Commission (IEC) has established the Human Body Model (HBM) ESD event that will aid designers in creating sufficient Protection in electrostatic applications. AS ILLUSTRATED IN THE TABLE BELOW, the IEC defined the HBM ESD discharge impulse with four levels, as per standard IEC 61000-4-2.
LevelContact Voltage (BV)Air Discharge Voltage (kV)Peak Contact Current (A)Contact Current @30ns (A)Contact Current @60ns (A)
They can be as high as +8 KV contact and +15 kV air discharges to help with ESD disturbances within systems. A higher voltage is sometimes required for improved air discharge and contact specifications. This is because the human body model can exceed the range of n+-25 kV within static environments.
It has the lowest rise time of more than 1n and a decay time of 60n, as shown in the figure. To determine the most appropriate overvoltage and ESD level of Protection, engineers must consider what external disturbances (ESD, EFT, surge, or lightning) affect the device during installation or operation. Manufacturers of the Integrated Circuits (IC) that have electrostatic sensitive devices design the level of Protection within the IC. This is intended to improve resistance against events of overvoltage during manufacturing. However, adding protection circuits can cost significantly, and to cut down on expenses, IC manufacturers often design only to the Level 1 standard, which protects against a contact voltage of 1-2 kV. The actual HBM ESD voltages could be higher than +15 kV, which can damage the IC, so a properly designed protection requires a level 1 specification as a secondary security scheme. A primary protector is needed to protect against higher +-8 kV contact air impulses.
It is essential to think about the following factors when selecting ESD protection:
- The trigger voltage is applied before the device that protects you will be activated.
- The voltage at which the overshoot is generated by the device that protects
- The voltage at which the clamping is applied to the Protection
Overvoltage Protection for Data Lines
Because of inert components like capacitors and inductors used in power supply systems, ESD protection is usually accomplished without additional details. The capacitance of a protection device is a problem when it comes to data lines in which higher speeds are being developed. The series resistance, along with the load capacitance, is the first-order filter that favors the rising and falling edges. Reducing the effective series resistance assists in setting the copper’s dimensions. However, reductions in capacitance effectiveness are the most significant factor in achieving the expected high transmission rates.
USB port protection
Universal Serial Bus (USB) was adopted as an established standard in the field of computer peripherals as well as digital media. Nowadays, USB ports are also used to charge and power transfer, nearly as they are used for data transfer. The USB specification offers a way that allows the use of a single USB port to power more than 127 USB peripherals through one host termination (PC). USB can also enable remote powering from the host of other accessories from the after-market, like travel lighting, mobile chargers for phones, and portable drives. USB 1.1 will allow data transfer speeds of up to 12 Mbps. USB 2.0 can provide up to 480Mbps, and the latest USB 3.0 will enable speeds up to five Gbps which is why it’s vital to utilize low capacitance TVS diodes to protect against overvoltage to safeguard the system from malfunctions like hot-swapping, short circuits, ESD transients, and faulty equipment.
This ProTek Devices single-port device PLR0502 was created to offer ESD Protection on the 5V Vbus line used for USB 1.1 and 2.0. It accomplishes this using an extremely low capacitance of 0.6 1 pF maximum per data line while ensuring zero leakage current. In dual USB ports, The PLR0504F should be a dual USB port. This device has no impact on the data transfer rate for higher-frequency applications, including USB 2.0 standard, with a speed of 480 Mbps.
The launch of the USB 3.0 standard in November 2008 was the next generation of performance by extending the lines for transmission to three differential pairs (from one provided in the 2.0 ages). It is important to note that the USB 3.0 specification calls for complete USB 2.0 compatibility (HS, FS, and LS). Also, it requires the Ultra-high speed data connection known as SuperSpeed. SuperSpeed operates with two separate data lines for downloading (Host = Device, referred to as TX direction) and uploading in the RX direction (Device Host). The maximum speed for data transmission for data transfer in SuperSpeed mode can be reached at 5 Gbit/sec. A combination of USB 2.0 capability and the new SuperSpeed method requires a new cable design. This is to support three distinct signal lines (TX+/Tx-, RX+/Rx D+/D-). The VCC and the GND line also complete the cable set. The PLR0506 inside a DFN-8 box includes six ESD protection channels with a meager 0.8pF capacitance rating, which aligns with the transmission requirements. The Vbus line is also protected by using the GBLC05C or PSD05C devices.
HDMI port protection
HDMI is the standard digital connection for consumer electronics. It provides an excellent audio and video signal on one cable. The HDMI typically demands the transmission speed to be high, which is around 18 Gbps. ESD PROTECTION IS USUALLY NEEDED because HDMI applications are utilized in consumer goods and devices. ProTek Devices offers two solutions for HDMI designers to provide ESD protection for twelve data lines. Protel offers two options to safeguard 12 lines of data. Utilizing two PLR0506 with six lines of ESD protection each, or using three PLR0524P with four lines of ESD Protection per. Both solutions require PSD05HP to provide ESD and surge safety for the Vbus line.
Protection of Ethernet ports
The essential element of Protection you should consider when considering Ethernet ports is the transformer that offers isolation of the interface and the termination capacitor between the drive circuitry and the communication lines. When the Ethernet transformer can handle the test of impulses without failing, Protection will be needed on the secondary end of the transformer. This will protect your Ethernet IC from energy transfer before the transformer reaches saturation. A standard Ethernet transformer can withstand 200-300 A 2/10ms of energy before it fails. Secondary Protection must handle this power (including ESD & surge transients) without letting in too much voltage and stressing the IC. TVS diodes can be considered secondary Protection. This device could include ProTek Devices’ PLR0504F. The primary goal of this Protection is to minimize the energy source at the point of entry to the device (RJ-45 socket) so that less stress is imposed on the circuit. The SRV25-4 device placed near the RJ-45 socket will give you a maximum of 40A (8/20ms) of surge rating and ESD protection up to 25kV. Its 3.5pF small capacitance can keep high-speed transmission rates. The SRV25-4 device can fulfill the ESD, EFT, and surge protection demands. A different high surge rating choice is to use ProTek Devices’ PLC03-3.3 (for 3.3 V systems) or PLC03-6 (6 V for 5 V systems). They offer the option of integrating a TVS diode and a bridge diode.
The following comparison is made to give a general overview of the various possibilities for protecting high-speed data lines.