Do TVS diodes have positive and negative terminals? Method for distinguishing the positive and negative poles of TVS tubes

Introduction to TVS diodes

TVS diode, also known as transient suppression diode, is a widely used new type of high-efficiency circuit protection device, which has extremely fast response time (sub nanosecond level) and considerable surge absorption capability. When its two ends are subjected to instantaneous high-energy shocks, TVS can quickly change the impedance value between the two ends from high impedance to low impedance, absorbing a momentary high current and clamping the voltage at both ends to a predetermined value, thereby protecting the subsequent circuit components from the impact of transient high voltage spikes.

Classification and characteristics of TVS diodes:

TVS diode classification:

TVS devices can be divided into unipolar and bipolar types based on polarity, and can be classified into general-purpose devices suitable for various circuits and specialized devices suitable for special circuits based on their applications. Such as various AC voltage protectors 4-20mA current protector, data line protector, coaxial cable protector, telephone protector, etc. If classified by packaging and internal structure, it can be divided into axial lead diodes, dual in-line TVS arrays (suitable for multi wire protection), patch type, component type, and high-power module type.

TVS diode features:

(1) Adding TVS diodes to the signal and power lines can prevent the failure of microprocessors or microcontrollers caused by momentary surges, such as electrostatic discharge effects, AC power surges, and noise from switching power supplies.

(2) The electrostatic discharge effect can release pulses exceeding 10000V and 60A, and can last for 10ms; However, typical TTL devices will be damaged when exposed to 10V pulses exceeding 30ms. By using TVS diodes, it is possible to effectively absorb pulses that can cause device damage and eliminate interference caused by switches between buses (Crosstalk).

(3) Placing the TVS diode between the signal line and ground can prevent unnecessary noise from affecting the data and control bus.

Do TVS diodes have positive and negative terminals? Method for distinguishing the positive and negative poles of TVS diodes:

Unidirectional TVS diodes have a difference in positive and negative poles, and their usage is the same as that of voltage regulators. Bidirectional TVS diodes have no difference in positive and negative poles. When tested with a unidirectional TVS meter, its characteristics are similar to those of a regular diode, and it also conducts unidirectionally with a forward conduction of about 0.6V voltage drop. When the direction is low voltage, it is infinitely large, and only conducts when it exceeds its avalanche voltage. A bidirectional TVS is equivalent to the combination of two unidirectional TVS with consistent characteristics, and it does not conduct when tested with a regular meter.

1、 Measure with a multimeter

Measure the gear of the diode, with one side conducting in one direction and voltage on both sides in both directions;

Measurement of DC, bidirectional symmetry, unidirectional only reverse is avalanche breakdown characteristic, usually measured at 1mA.

After amplification, all TVS diodes will have a cathode wire, which is used to distinguish the positive and negative poles of the diode and is independent of both directions.

2、 Differences in single/bidirectional usage

1. Unidirectional use in DC. Two way use for communication;

2. TVS diodes can be divided into unidirectional and bidirectional types. The characteristics of unidirectional TVS diodes are similar to those of Zener diodes, while the characteristics of bidirectional TVS diodes are equivalent to two Zener diodes connected in reverse series;

3. The unidirectional capacitance Cj is larger than the bidirectional capacitance Cj;

4. All USB data cables are bidirectional;

5. The current curves are different.