Network interface ESD ESD protection scheme design ideas analysis
ESD protection of all kinds of electronic | network interface is very important, and the static ESD diode is a very effective protection device, has its unique advantages compared with other devices, but in the application for the protection of different objects to use devices should be different because the electrostatic port may be subject to the impact of different, different degree of protection the device requirements are also different. We should pay attention to the corresponding parameter identification and various manufacturers of different design, but also a reasonable PCB layout. This paper introduces how to use ESD devices in ESD protection diode static electronic network interface in |.

The electronic | network interface such as T1/E1, T3/E3 line card and DS3 interface, STS-1 interface, ISDN S/T interface, ISDN U interface, 10/100 Ethernet, the transmission rate of high frequency, highly susceptible to electrostatic discharge (ESD) impact, if there is no choice suitable protection device, may cause the machine performance is not stable, or damage. Worse is not found the exact reason, the user mistakenly believe that product quality problems and damage corporate reputation.
Under normal circumstances, exposed to the outside of the portable device may contact the human body ports require anti-static protection, such as keyboard, power interface, data port, I/O mouth, etc.. Now more common ESD standard is IEC61000-4-2, the application of human static mode, the test voltage range of 2kV ~ 15kV (air discharge), peak current of 20A/ns, the pulse duration of not more than 60ns. The total energy produced under such pulses is not more than a few hundred micro coke, but is sufficient to damage sensitive components.

IC electronic devices | products is widely used in small volume high integration, products, precision processing technology make the silicon oxide layer is very thin, which is easy to breakdown, some damage will be around 20V. Traditional protection methods are no longer applicable, and some may even cause interference to equipment performance. Can be used for ESD protection device for electronic | network products there are many, such as the designer can use discrete devices to build the protection circuit, but due to the electronic | network products for space limited and avoid loop self inductance, this method has gradually been replaced by more integrated devices. Multilayer metal oxide varistor, ceramic capacitor and SMD diode can effectively guard, characteristics and their performance are different, unique performance of electrostatic ESD diode in such applications to win more and more market for the. The following is the specific characteristics of TG SO-08 package ESD tage diode ESD06V08S-4L electrostatic:

ESD06V08S-4L parameters:
Package: SO-08
Voltage: 6V
Clamp voltage: 15V
Capacitance value: 25pF
Power: 2000W, more ESD electrostatic model specification diode can directly access from electronic official website.

Characteristics of ESD06V08S-4L:
1, according to (tp=8/20 s) line, peak pulse power of 2000W
2, two lines of common mode and differential mode
3, suitable for low capacitance of the high speed interface
4, low clamping voltage and working voltage
5, in compliance with RoHS
6, Bellcore standard 1089 (internal construction) 100A (2/10 s)
7, ITU K.20 Ipp=40A (5/310 s)
8, IEC61000-4-2 (ESD) + 15kV (air), + 8kV (contact)
9, IEC61000-4-4 (EFT) 40A (5/50, s)
10, IEC61000-4-5 (Lightning) 100A (8/20 s)

The application of ESD06V08S-4L products:
1, T1/E1 line card
2, T3/E3 and DS3 interface
3, STS-1 interface
4, S/T ISDN interface
5, U ISDN interface
6, 10/100 Ethernet

Regardless of how electrostatic inhibitors are selected, their layout on the circuit board is very important. The conductor length before the diode layout should be minimized because the fast (0.7ns) ESD discharge current induces a high voltage spike on the inductive wiring, affecting the performance of the ESD protection. In addition, a fast ESD pulse may induce an induced voltage between adjacent (parallel) conductors on the circuit board. If the above occurs, as will not be protected, because the inductive voltage path will become another way to allow the surge to reach IC. Therefore, the protected input lines should not be placed next to other individual, unprotected lines. Recommended ESD suppression device PCB layout scheme should be: as far as possible to filter out all the I/O port interference signal, close to the connector / contact PCB side.

When wiring, shorten the connection between high-frequency components as far as possible, try to reduce their distribution parameters and electromagnetic interference between each other; input and output wire should avoid adjacent parallel. The best line between the ground, so as to avoid the occurrence of feedback coupling. Figure two is the wiring optimization recommendations. For electronic | network products, all kinds of complexity of integrated circuit and precision improvement so that they are more sensitive to ESD, the design of general circuit is no longer suitable for the past. PCB layout is the most important in the use of ESD to avoid self harm and ESD electrostatic protection diodes. The ESD design is likely to cause the parasitic self inductance in the loop, there will be a strong impact on the voltage loop, to exceed the tolerance limits of IC damage. Self induction voltage and power intensity is proportional to the load change generated by the impact of the ESD transient characteristics easy to induce high strength self inductance. The basic principle of reducing the parasitic inductance is as far as possible to shorten the shunt loop must be considered to include the grounding circuit, ESD diode and the protection circuit between the loop, and all factors of the TVS pathway to the interface. Therefore, ESD should be as close as possible to the interface with the static diode (discharge directly to the nearest ESD interference, avoid the string into the circuit), and as close as possible to the protected line (painting principle to close to the protected chip), this will reduce the inductance coupling to other adjacent line opportunities.