Transient voltage suppression diode (transient voltage suppressor) is a diode, can protect sensitive components and has fast response time and very high surge absorbing ability. When the reverse transient overvoltage pulse is at both ends of the television, at high speed to between the ends of the high impedance to low impedance, to absorb a large transient current and voltage clamped in a predetermined value, in order to effectively protect the circuit components from damage in this paper tells the TV diode characteristics and key parameters. 1 Characteristics and main parameters of the television diode device
1.1 the characteristics of the device of TV diode
Under the conditions of the reverse application, the TV diode has a high impedance state to the protected line. When the instantaneous voltage exceeds the breakdown voltage, diode TV will provide a low impedance path, and through the large current which flow to protected components of transient current shunt to TVS diode and also protected components at both ends of the voltage limit in TV voltage clamp. When the overvoltage condition disappears, the TV diode is restored to the high impedance state. Compared with ceramic capacitors, the TV diode can withstand the voltage of 15 kV, but the capacity of the ceramic capacitor is relatively weak. 5 kV impact will cause about 10% ceramic capacitor failure, and to 10 kV, the damage rate will be as high as 60%.
1.2 main parameters of TV diode devices
(1) minimum breakdown voltage VBR
The voltage at both ends of the television is called the minimum breakdown voltage, in this region, when the current flows through the specified current, the television diode is in a low impedance path. At 25 C, below this voltage, the television diode is not going to happen.
(2) rated reverse turn off voltage VWM
VWM is a television diode in the normal state can withstand the voltage, this voltage should be greater than or equal to the normal operating voltage of the protected circuit. But it also needs to be as close as possible to the normal operating voltage of the protection circuit, so that it will not work in the face of the whole circuit to make the entire circuit before the threat. According to the VBR of the VBR and the standard value of the discrete degree, can be divided into 5% and two for 10%, for 5% of the VBR, VWM = 0.85vbr legs; and for 10% of the VWM, VBR = 0.81vbr.
(3) maximum peak pulse current IPP
IPP is a TV diode in the reverse state when working in the specified pulse conditions, the device allows the maximum peak current through the pulse. (4) clamp voltage VC
When the pulse peak current IPP flows through the diode TV, the maximum voltage at both ends of the value of said clamping voltage VC, VC and IPP reflects the TVS Diode surge suppression ability. Usually the VC and VBR is called the clamping factor (coefficient), its value is generally at 1.2 ~ 1.4. In practical use, the VC should not be greater than the maximum allowable safe voltage of the protected circuit, otherwise the device will face the possibility of being damaged.
(5) maximum peak pulse power consumption PM
The afternoon is usually the product of the largest peak pulse current IPP and clamp voltage VC, which is the maximum peak pulse power. It is the maximum peak pulse power consumption of the television diode. Under a given maximum clamping voltage, the greater the power consumption of PM, the greater the ability to withstand the surge current. In addition, the peak pulse power consumption is also related to the pulse waveform, pulse duration and environment temperature. Moreover, the transient pulse that the television diode can bear is not repeated.
(6) capacity C
The capacitance of the television diode is determined by the cross-sectional area and the bias voltage of the silicon wafer, which is measured at a specific frequency of 1 MHz. The size of C is proportional to the current capacity of the television diode, and the C is too large, which will cause the signal attenuation. Therefore, the capacitor C is an important parameter of the data interface circuit.
(7) leakage current IR
Infrared is the maximum reverse voltage applied to the television diode when the leakage current of the television tube. This leakage current is an important parameter when the TV diode is used in the high impedance circuit.
Concluding remarks
This paper mainly describes the characteristics and the main parameters of the TV device, in order to deepen the understanding of the circuit designers to TV, designed to provide the basis for the design of high reliability. Although the current TV in the domestic application is in the promotion stage, but we have reason to believe that, with more and more designers on the television show excellent performance of the deepening understanding and TV, TV devices will eventually get extremely extensive application at the same time, deep Shenzhen tergytech thank you for the new and old customers the company support!