TVS Application Guide Transient Voltage Suppression Diode Application Guide Chapter 1 Characteristics, Electrical Characteristics and Main Electrical Parameters of TVS Devices 1. Characteristics of TVS Devices Transient (transient) voltage suppression diodes are referred to as TVS devices. Under the specified reverse application conditions, when subjected to a high-energy instantaneous overvoltage pulse, its working impedance can immediately drop to a very low conduction value, allowing large currents to pass through and clamping the voltage to a predetermined level, thereby effectively protecting the precision components in the electronic circuit from damage. The instantaneous pulse power that TVS can withstand can reach kilowatts, and its clamping response time is only 1ps (10-12S). The forward surge current allowed by TVS can reach 50~200A under the conditions of TA=250C and T=10ms. Bidirectional TVS can absorb instantaneous large pulse power in both positive and negative directions and clamp the voltage to a predetermined level. Bidirectional TVS is suitable for AC circuits, and unidirectional TVS is generally used for DC circuits. 2. Electrical characteristics of TVS devices 1. The VI characteristics of unidirectional TVS are shown in Figure 1-1. The forward characteristics of unidirectional TVS are the same as those of ordinary voltage-stabilizing diodes. The reverse breakdown inflection point is close to a \"right angle\" for hard breakdown, which is a typical PN junction avalanche device. The curve segment corresponding to the breakdown point to the VC value shows that when there is an instantaneous overvoltage pulse, the current of the device increases sharply and the reverse voltage rises to the clamping voltage value and remains at this level. 2. The VI characteristics of bidirectional TVS are shown in Figure 1-2. The VI characteristic curve of the bidirectional TVS is like a \"back-to-back\" combination of two unidirectional TVSs. Both the forward and reverse directions have the same avalanche breakdown characteristics and clamping characteristics. The symmetrical relationship between the breakdown voltages on the forward and reverse sides is: 0.9≤V(BR)(positive)/V(BR)(reverse)≤1.1. Once the interference voltage applied to its two ends exceeds the clamping voltage VC, it will be suppressed immediately. The bidirectional TVS is very convenient to use in AC circuits. 3. Main electrical parameters of TVS devices 1. Breakdown voltage V(BR) The voltage across the device measured in the region where breakdown occurs under the specified test current I(BR) is called the breakdown voltage. In this region, the diode becomes a low-impedance path. 2. Maximum reverse pulse peak current IPP When working in reverse, under the specified pulse conditions, the device is allowed to pass the maximum pulse peak current. The product of IPP and the maximum clamping voltage VC(MAX) is the maximum value of the transient pulse power. ……
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