What are the main electrical parameters of TVS diodee?

The main electrical parameters of the TVS diodee

There are several main factors that should be considered when selecting a TVS:

(1) If the TVS is likely to withstand the impulse voltage (surge voltage) from two directions, the bipolar one should be selected, otherwise the unipolar one should be selected.

(2) The Vc value of the selected TVS should be lower than the maximum voltage of the protected components. Vc is the voltage of the diode in the cut-off state, that is, the voltage that passes through the TVS in the ESD shock state, which cannot be greater than the tolerable limit voltage of the protected circuit, otherwise the device is in danger of being damaged.

(3) The TVS should not be in a breakdown state under normal working conditions, and it is better to be below VR, and the requirements of VR and VC should be comprehensively considered to select the appropriate TVS.

Regulator diodees

(4) If you know the more accurate inrush current IPP, you can use VCIpp to determine the power; If the approximate range of the IPP is uncertain, it is better to use a TVS with higher power. PM is the maximum peak pulse power dissipation that the TVS can withstand. Under a given maximum clamping voltage, the greater the power dissipation PM is, the greater the inrush current capacity. The lower the clamping voltage VC for a given power dissipation PM, the greater its inrush current tolerance. In addition, the peak pulse power consumption is also related to the pulse waveform, duration, and ambient temperature. (5) The transient pulses that the TVS can withstand are non-repetitive, and the specified pulse repetition rate (the ratio of duration to intermittent time) is 0.01%. If there are repetitive pulses in the circuit, the accumulation of pulse power should be considered, otherwise the TVS may be damaged.

(6) For the protection of small current loads, the current limiting resistance can be consciously increased in the line, as long as the resistance value of the current limiting resistor is appropriate, it will generally not affect the normal operation of the line, but the current generated by the current limiting resistance to the interference will be greatly reduced. However, it is possible to use a TVS diodee with a small peak power to protect the low-current load line.

(7) Capacitance C is determined by the TVS avalanche junction cross-section, which is measured at a specific frequency of 1 MHz. The size of C is directly proportional to the current tolerance of the TVS, and too large C will attenuate the signal. Therefore, C is an important parameter for the selection of TVS for data interface circuits. For loops with higher data/signal frequencies, the greater the interference of the diode's capacitance to the circuit, the greater the noise formation or attenuation signal strength, so the capacitance range of the selected device needs to be determined according to the characteristics of the loop. In general, the capacitance of high-frequency circuits should be as small as possible (such as LCTVS, low-capacitance TVS, capacitance is not greater than 3 pF), and the capacitance of the capacitance can be higher than 40 pF for circuits with low capacitance requirements.

(8) In order to meet the IEC61000-4-2 international standard, TVS diodes must be able to handle ESD shocks of a minimum of 8 KV (MB, contact) and 15 kV (BM, air), and some semiconductor manufacturers use higher impact resistance standards for their products. For some portable device applications with special requirements, designers can select the device according to their needs.