Transient suppression diode characteristic parameters

characteristic:

The circuit symbol of TVS is the same as ordinary Zener diode. Its forward characteristic is the same as that of an ordinary diode; its reverse characteristic is a typical PN junction avalanche device.

Under the action of the transient peak pulse current, when the current flowing through the TVS rises from the original reverse leakage current ID to IR, the voltage present on its two poles rises from the rated reverse turn-off voltage VWM to the breakdown voltage VBR, and the TVS is breakdown. With the appearance of the peak pulse current, the current flowing through the TVS reaches the peak pulse current IPP. The voltage at its two poles is clamped below the predetermined maximum clamp voltage. After that, as the pulse current decays exponentially, the voltage of the TVS poles also drops continuously, and finally returns to the initial state. This is the whole process of TVS suppressing possible surge pulse power and protecting electronic components.

parameter:

①Maximum reverse leakage current ID and rated reverse shut-off voltage VWM.

VWM is the maximum continuous working DC or pulse voltage of the TVS. When this reverse voltage is added between the two poles of the TVS, it is in the reverse shut-off state, and the current flowing through it should be less than or equal to its maximum reverse leakage current ID.

②Minimum breakdown voltage VBR and breakdown current IR

VBR is the minimum avalanche voltage of TVS. At 25°C, TVS is non-conducting before this voltage. When the TVS flows through the specified 1mA current (IR), the voltage added between the two poles of the TVS is its minimum breakdown voltage VBR. According to the degree of dispersion between the VBR of TVS and the standard value, TVS can be divided into two types: ±5%VBR and ±10%VBR. For ±5%VBR, VWM=0.85VBR; for ±10%VBR, VWM=0.81VBR.

③Maximum clamping voltage VC and maximum peak pulse current IPP

When a pulse peak current IPP with a duration of 20 microseconds flows through the TVS, the maximum peak voltage that appears between its two poles is VC. It is a combination of the series resistance and the voltage rise due to the temperature coefficient. VC and IPP reflect the surge suppression capability of TVS devices. The ratio of VC to VBR is called the clamping factor, which is generally between 1.2 and 1.4.

④Capacity C

The capacitance C is determined by the TVS avalanche junction section and measured at a specific frequency of 1 MHz. The magnitude of C is directly proportional to the current carrying capacity of the TVS, too large C will attenuate the signal. Therefore, C is an important parameter for selecting TVS for the data interface circuit.

⑤Maximum peak pulse power consumption PM

PM is the maximum peak pulse dissipation power that the TVS can withstand. For the specified test pulse waveforms and various TVS PM values, please refer to the relevant product manuals. Under a given maximum clamping voltage, the greater the power consumption PM, the greater the surge current capacity; under the given power consumption PM, the lower the clamping voltage VC, the greater the surge current capacity big. In addition, the peak pulse power consumption is also related to the pulse shape, duration and ambient temperature. Moreover, the transient pulse that TVS can withstand is not repetitive. The pulse repetition frequency (the ratio of duration to intermittent time) specified by the device is 0.01%. If repetitive pulses appear in the circuit, the "accumulation" of pulse power should be considered. It may damage the TVS.

⑥ Clamping time TC

TC is the time for the voltage across the TVS to go from zero to the minimum breakdown voltage VBR. For unipolar TVS, it is generally 1×10-12 seconds; for bipolar TVS, it is generally 1×10-11 seconds.