Why is the positive terminal of the TVS diode connected to the negative terminal in the circuit?

Why is the positive terminal of the TVS diode connected to the negative terminal in the circuit?

Diodes are believed to be very familiar to everyone, and diodes generally have positive and negative poles. Today we will talk about why the positive pole of the TVS diode is connected to the negative pole in the circuit.

    Although the TVS  is similar to the regulator diode, but the two are not exactly the same, such as the PN junction, TVS diode than the PN junction area composed of the regulator diode, so it can withstand the reverse current is larger than the regulator diode, TVS diode forward surge current can even reach hundreds of amps, for example, for TVS diode 5KP54, its maximum pulse current can reach 50A, which is incomparable with the regulator diode, in addition, TVS diode instantaneous pulse power up to kilowatt level, The regulator diode power is generally only a few watts.

    In fact, TVS is a transient suppression diode, as the name implies, is able to instantly suppress high energy diode, combined with varistors may be better understood, this diode is a clamping diode, similar to the regulator , it also plays a clamping role, its principle is that under the action of reverse voltage can quickly reduce the high transient energy to the minimum value, the voltage clamping to a certain value, thereby protecting the post-level components or ESD-sensitive equipment.

    This kind of clamping diode has unidirectional and bidirectional, generally unidirectional TVS  is used to protect DC voltage, in DC occasions see more, pay attention to the circuit when its negative pole is connected to the positive pole of the voltage; The bidirectional TVS  can be regarded as being made of two unidirectional TVS reversed, it can not consider the voltage positive and negative in the circuit, because it can play a role in suppression, so if the circuit may come from two directions when the voltage is impacted, it is necessary to consider the use of bidirectional TVS , generally used in AC occasions, such as lightning protection, power supply voltage suppression, etc.

    One-way TVS and two-way TVS diode

    In addition to unidirectional and bidirectional these two or integrated chip form, this integrated chip integration is higher than single, so as to avoid putting in multiple single TVS s, generally this integrated chip is mostly used for a variety of high-speed signal processing circuits and data interface circuits, such as USB interface, various differential signal interfaces, video interfaces, etc.