Learn about difference between transient suppression diodes unidirectional

Learn about transient suppression diodes unidirectional and different points    

transient suppression diodes protect sensitive electronics from voltage transients caused by lightning surges and other transient voltage events, and are widely used in circuit protection today. And many customers do not know much about the product itself, such as what is one-way or two-way, and what are the differences between them. This has led to some customers having difficulty choosing.

    First, how to distinguish the single and bidirectional of TVS transient suppression diodes

    1. Look at the model. From the surface of the model alone, we can judge that although different brands have different naming methods, they all have rules:

    2. Look at the specifications, generally on the page. <1> bidirectional is bidirectional communication, <2> unidirectional is unidirectional communication,

    3. Measure with a multimeter

    <1> Measure the gear of the diode, one side is open, and there is voltage on both sides of the two directions;

    <2> Measured DC, bidirectional symmetry, one-way only reverse is avalanche breakdown characteristics, generally 1mA downward test.

    4. All TVS diode will have a cathode line after amplification, which is used to distinguish the positive and negative poles of the diode, and has nothing to do with single and bidirectional.

    Second, the difference in single/two-way use

    1. One-way use in DC. Two-way is used for communication; The unidirectional transient suppression diodes protection device can only protect the positive pulse or negative pulse, while the two-way TVS diode protection device is connected to be protected at one end

    The line, grounded at one end, and the ESD pulse, whether from the reverse or from the forward direction, is released, protecting the IC more effectively.

    2. TVS diode has unidirectional and bidirectional division, the forward characteristics of unidirectional TVS diode are the same as ordinary voltage regulator diodes, and the hard breakdown of approximately "right angle" at the reverse breakdown inflection point is typical

    PN avalanche. When there is a transient overvoltage pulse, the current of the device increases sharply and the reverse voltage rises to the clamping voltage value and remains at this level; V-I characteristics of bidirectional TVS diode

    The curve is like a "back-to-back" combination of two unidirectional TVS, and its positive and negative directions have the same avalanche breakdown characteristics and clamping characteristics, and the symmetrical relationship between the breakdown voltages on the front and back sides is 0.9≤VBR (positive)/VBR (inverse) ≤1.1. As soon as the interference voltage applied across it exceeds the clamping voltage, Vc is immediately suppressed.

    3. Inter-pole capacitance Cj

    Unidirectional is larger than bidirectional, taking LRC as an example, the unidirectional capacitor C has 65PF, and the bidirectional only 15PF;

    4. All two-way use on USB data cable;

    5. The current curve is different. The circuit symbol of the unidirectional TVS diode is the same as that of the ordinary regulator diode, and its forward characteristics are the same as those of ordinary diodes, and the reverse characteristics are typical PN avalanche devices. Bidirectional diodes are both forward and reverse typical PN avalanche devices.