Specific explanation and selection application of TVs parameters

First, to understand the parameters of TVs tube, we take Littelfuse 5.0SMDJ series as an example.

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Figure 1

Figure 2

• Maximum Peak impulse power Maximum peak pulse power

PPpmPeak Pulse Power is the instantaneous maximum power value on an ESD device。 Determined by the maximum clamping voltage VC and at this time the Pulse peak current IPP.

the maximum pulse peak power is 5000W, which can be seen in the 5.0SMDJ series. It is also possible to see that each model under this series has a basic vc*ipp of 5000W. And the greater the VC bear. The smaller the IPP.

• Maximum Pulsed peak current IPP

The maximum pulse peak current that TVs can withstand.

5.0SMDJ13A maximum pulse current is 233A.

• Maximum clamping voltage VC (residual pressure)

when the duration is 20mS Pulse Peak current IPpflow through TVS. Maximum peak voltage at both endsto VC. Also known as the maximum protection voltage.

5.0SMDJ series different models of VC are not the same. The maximum protection voltage of the 5.0smdj13a is 21.5V.

• Maximum reverse leakage current IR

TVS maximum reverse leakage current, can be seen5.0smdj13a Maximum Reverse leakage current is 500uA

• Maximum reverse operating voltage VRWM or VR.

When the maximum reverse leakage current IR flows through the TVs, the TVs voltage is the maximum reverse operating voltage.5.0smdj13a maximum reverse operating voltage is 13V.

• Test current IT

The test current IT determines the TVs reverse breakdown voltage VBR.

• Reverse breakdown voltage VBR

The TVs tube passes the voltage specified in the test current it, which represents the signal voltage that the TVs tube is conducting, that is, from the point the device enters the avalanche breakdown.

• Knot Capacitance CJ

When protecting the fast signal. Need to consider the effect of the junction capacitance.
ii. selection and application of TVs tube1, TVs is used to protect the inrush current, assuming that the maximum current to protect the IPP best. first determine the IPP for TVs. 2, then nextDetermine the DC voltage or continuous operating voltage of the circuit to be protected. The assumption is alternating current. The maximum value should be calculated. That is, *1.414 with valid values. 3, according to the known operating voltage of 2, select the VRWM of TVs, require VRWM to be greater than the operating voltage, otherwise the operating voltage greater than VRWM will cause TVs reverse leakage current increase. Proximity to conduction, or avalanche breakdown, affects normal circuit operation. 4, the selected TVs maximum clamping voltage VC can not be greater than the protection circuit can withstand the maximum voltage. Otherwise, when the TVs clamp on the VC will cause damage to the circuit. 5, of which 2-4 steps can precede 1. If IPP is not known, the IPP can be determined based on the power of the signal. 6, unipolar or bipolar-often this misunderstanding is that two-way TVs are used to suppress reverse surge pulses. In fact, that's not true.

Two-way TVs are used for alternating current or for applications from positive or negative bidirectional pulses.

TVs are also sometimes used to reduce capacitance. Assuming that the circuit has only a forward level signal, then one-way TVs is sufficient. The TVs operates in the following way: when a positive surge occurs, TVs is in reverse avalanche breakdown, and when the reverse surges, the TVs are similar to the forward bias diodes, and absorb the surge energy.

This time you need to take a tour of the TVs ' forward-flow peak current. IFSM. The 5.0SMDJ series has a maximum forward-guide current of 300A.

Third, surge waveform 10/1000us and 8/20US.
10/1000US and 8/20US are two different types of surge test waveforms. The energy of the two waveforms is different.
The 10/1000US is a duration of 1000us and the rising edge time is 10us.

The 8/20us is duration 20us and the rising edge time is 8us.

Figure 2 shows that the maximum power of the TVs is 5000W, which is measured in the waveform energy of the surge 10/1000US. IPP is based on the results obtained from the 10/1000 waveform energy. When the surge waveform is 8/20us. The corresponding number of references will become larger.
The figure can be seen when the 1000us waveform, can withstand the maximum power of 5KW.

When the test waveform is 20us. The maximum power to withstand is 20KW. Assuming that the VC is unchanged, the maximum peak current that can be sustained will become larger and the IPP becomes 4 times times the original. 20/5=4

Specific explanation and selection application of TVs parameters