TVS tube is an important circuit protection device of electronic products, mobile phones, computers, smart bracelet, switching power supplies, digital electronics and other industries, loved by electronic engineers, due to the TVS tube with anti-static, anti-surge function, a birth , it quickly became popular electronics market,
But, with so many electronic products market model, how to give yourself a time to choose the right product TVS tube models and parameters, one thing has become so buyers headache, how to choose a suitable own products TVS tube parameters that, let Li Xin deep
Electronic take you to discover Selection of parameters TVS tube, so you do not purchase a headache.
TVS tube Selection of parameters:
1. The minimum breakdown current and breakdown voltage VBR IR. VBR is the minimum breakdown voltage TVS, at 25 ℃, below this voltage will not cause an avalanche TVS. When TVS 1mA current flowing through a predetermined (IR), a voltage applied to the bipolar TVS its minimum breakdown voltage VBR. Press VBR standard value and degree of dispersion of TVS, the VBR can be 5% and 10% of the two. For VBR is 5%, VWM = 0.85VBR; 10% for VBR is, VWM = 0.81VBR.
2. The maximum reverse leakage current and the rated reverse ID cutoff voltage VWM. VWM is subjected to a normal state when the diode voltage which is greater than or equal protection of the normal operation voltage of the circuit, or loop cutoff voltage diodes will continue; but it needs to be as close to the normal operating voltage of the protected circuit, so it does not make the entire loop in the face of the threat of over-voltage TVS previous work. When this voltage is turned off VWM rated reverse between two electrodes applied to it in the reverse TVS off state, the current flowing through it is equal to or less than the maximum reverse leakage current ID.
3. VC maximum clamping voltage and a maximum peak pulse current IPP. When the duration of 20ms pulse peak current flowing through the IPP TVS, the maximum peak voltage across it appears as VC. VC, IPP reflects the TVS surge suppression. The ratio is called VBR VC and clamp factor, typically between 1.2 to 1.4. VC is the voltage of the diode provided in the off state, i.e. a state when an ESD voltage by TVS, it can not be greater than the tolerance limit of the protection circuit voltage, or at risk of being damaged element.
4.Pppm pulse power rating, which is based on the maximum cut-off voltage and a peak pulse current at that time. For handheld devices, in general, the 500W TVS sufficient. PM is the maximum peak pulse power TVS can withstand the maximum peak pulse power consumption value. Under certain maximum clamping voltage, the greater the power consumption PM, the greater its ability to withstand surge current. Under certain power PM, the lower clamp voltage VC, the greater its ability to withstand surge current. Further, the peak pulse power is also related to the pulse shape, duration, and ambient temperature. Further, TVS diodes can not withstand the transient pulse is repeated, a predetermined pulse repeat frequency component (ratio of duration of intermittent time) was 0.01%. If the repetitive pulse occurs within the circuit, consider the cumulative pulse power, could damage the TVS.
The amount of the capacitor C. The capacitor C is determined by the amount of TVS avalanche junction section, it is measured at a specific frequency of 1MHz. TVS size C with a current proportional to the capacity, C too will signal attenuation. Thus, C is a data interface circuit used the diode tvs important parameter. The higher capacitor for data / frequency signal circuit, a diode capacitor circuit, the greater interference, or noise attenuating the signal strength is formed, it is necessary to determine the range of the capacitor element is selected according to the characteristics of the circuit. Frequency circuit generally selected capacitor should be as small (e.g. LCTVS, low capacitor TVS, the capacitor is no greater than 3pF), and capacitor selection circuit capacitor may be less demanding than 40pF.