As a protection device, TVS tube can effectively prevent electrostatic breakdown protection circuit. When choosing a TVS tube, you must pay attention to its related parameters, otherwise unexpected problems will occur. First understand the parameters of TVS: VRWM, VBR, Vc, Ipp, Cd are important parameters for ESD/TVS device selection. 1.Vc----Clamping voltage @Ipp (maximum clamping voltage) The Vc clamping voltage refers to the voltage clamped after the pulse voltage passes through the ESD protection device at a specific Ipp current. For PESD5V0L2BT, when Ipp is 1A, Vc is 10V. If an instantaneous interference signal of 1000V passes through PESD5V0L2BT, the line voltage will be clamped at about 10V. 2.VRWM----Working Peak Reverse Voltage (maximum reverse working voltage) Ir----Maximum Reverse Leakage Current @ VRWM (Maximum Reverse Leakage Current) Vrwm means that under the specified Ir, the voltage across the TVS device becomes the maximum reverse working voltage. Usually Vrwm=(0.8~0.9)Vbr. At this voltage, the power consumption of the device is very small. When using, make Vrwm not lower than the normal working voltage of the protected device or circuit. Generally, Vrwm will be lower than 85%Vc and higher than the normal operating voltage, so that TVS can be connected to the circuit without affecting the normal circuit operation. 3.VBR----Breakdown Voltage @ IT (reverse breakdown voltage) The voltage when the TVS tube passes the specified test current It, which is the mark voltage indicating that the TVS tube is turned on, that is, the device enters an avalanche breakdown from this point. 4. Ppp----Maximum Peak Pulse Power (Maximum Peak Pulse Power) The PPP peak pulse power is the maximum power value that can be passed instantaneously on the ESD device. As shown in the figure, the peak power of NUP2105 is 8/20us pulse wave (8us reaches 100%Ipp, 20us reaches 50%Ipp), and the maximum power that the protection device can withstand is 350w. 5. Cj ----Junction Capacitance (junction capacitance) 6.IT---- Test Current (test current) Under this current value, the reverse of the device is specified 7. One-way protection and two-way protection As shown in the figure, the unidirectional protection device can only protect against positive or negative pulses, while the two-way protection device is connected to the circuit to be protected at one end and grounded at the other end. The ESD pulse from the reverse direction or the forward direction is released. Effectively protect the IC. With these main parameters, you can basically know how to choose a TVS suitable for your circuit. Vc and Ipp reflect the surge suppression capability of TVS devices. When the TVS is subjected to the rated instantaneous peak pulse current Ipp, the maximum instantaneous voltage value that may be on the device, that is, the maximum clamping voltage is Vc. At this time, if the pulse time is the specified standard value, the maximum peak pulse power of TVS is: PM=Vc*Ipp. Therefore, before selecting TVS, it is best to have a rough understanding of the type of pulse generated in the line, whether it is a single pulse or a complex pulse, the rise time of the pulse, pulse width, peak value, etc., in order to determine Vc, Ipp, PM. Generally, it is determined that VRWM should be equal to or slightly higher than the normal working voltage of the circuit to ensure that the TVS connection will not affect the normal operation. In the AC line, it needs to be determined according to the squar(2) (ie 1.414) times of the normal working voltage, that is, the peak value. VBR cannot be less than the maximum allowable operating voltage of the circuit. Otherwise, the TVS will enter an avalanche and the leakage current will increase, which will affect the operation of the circuit. If it is used as IO pin protection, it is necessary to carefully study Cj and insert loss, which will change the phase and strength of the signal and may cause unstable work. In addition, there are two-way TVS tubes, and the two-way parameters are also applicable. Brake Disc For LEXUS Lexus Brake Disc,Lexus Auto Brake Disc,Lexus Car Brake Disc,Lexus Automobile Brake Disc Zhoushan Shenying Filter Manufacture Co., Ltd. , https://www.renkenfilter.com
