Only PCB Board layout optimization to improve ESD protection capability is very limited, in order to ensure that the whole system has a better ESD protection capability, external ESD protection devices is essential. Effective ESD protection can be selected according to the specific needs of different programmes. Typical ESD protection devices in the following categories:
(1) the resistive and capacitive components. By access on each signal line of resistive and capacitive components, can play a role in the ESD shield. Series resistance can inhibit the peak current of the moment and join the capacitor is able to limit the peak instantaneous voltage.
(2) clamp diode. Through two diodes can be positive and negative polarity between transient voltage clamped in a certain range, combined with series resistance provides the power load, ESD protection so as to play a positive and negative polarity.
(3) the Zener diode. Despite the diode is not designed specifically for ESD applications, but its characteristics it has some positive and negative polarity ESD protection. Its shortcomings are. N knots smaller and cannot bear a greater peak current, in addition to its parasitic capacitance is large, have the potential to affect the normal operation of the circuit.
(4) a transient voltage suppressor. Transient voltage suppressor or TVS tube, is a solid state diode for ESD protection design. TVS Canal is characterized by short response time, leakage current is very small, is ideal for protecting devices.
(5) gas discharge tube (GDT). Gas discharge tube used a certain tightness of glass or ceramic, as a shell. Tube full of stable gases such as neon or argon, in order to maintain a certain degree of insulation. Advantages of gas discharge tubes are big, the parasitic capacitance of the insulation resistance is small, reversible, but the disadvantage is that the speed of response and life are less than ideal, and performance will gradually decay over time.