Questions about TVS breakdown voltage VBR and clamping voltage VC

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Questions about TVS breakdown voltage VBR and clamping voltage VC [Copy link]

As shown in Figure 1 below, ESD122DMXR is used for surge protection of HDMI differential lines (Figure 1). Now there are the following questions:

The operating voltage of the HDMI controller high-speed pin is 0~3.3V (see the red box in Figure 2). The breakdown voltage and clamping voltage of ESD122DMXR are both greater than 3.3V (see the red box in Figure 3).

My question is, the breakdown voltage and clamping voltage of TVS are both greater than the allowable voltage of the differential line. Can it still play a protective role?

If a surge occurs, and the clamping voltage VC is greater than 3.3V, won't the differential line pins (TMDS D2+/TMDS D2-) be burned? Thank you!

qwqwqw2088

maychang

"The breakdown voltage and clamping voltage of TVS are both greater than the allowable voltage of the differential line. Can it still provide protection?"

The red box in Figure 2 shows that 3.3V is the working voltage of the differential line. However, voltage exceeding this value may not cause damage. The voltage value that causes damage is higher than 3.3V. Therefore, TVS still has a protective effect.

However, if the TVS breakdown voltage is selected to be higher, the differential line may be damaged before the TVS breaks down. In this case, there is of course no protection.

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qwqwqw2088 posted on 2022-3-18 11:00

Sir, I understand this picture. Now my question is that the clamping voltage VC=6.4~8.4V of TVS (see the red box in Figure 3 above) is greater than the maximum allowable voltage of the protected circuit 3.3V (see the red box in Figure 2 above). I don't understand this. Please guide me, thank you!

qwqwqw2088

xiaxingxing posted on 2022-3-18 12:31 Boss, I understand this picture. Now my question is, the clamping voltage VC=6.4~8.4V of TVS (see the red box in Figure 3 above) is greater than the protected voltage...

If you understand, you can make judgments

The cut-off voltage of the TVS tube is slightly higher than the protection working voltage

3.3V protection, generally 3.6V~5V TVS can be used, just have enough reserve

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maychang published on 2022-3-18 12:29 "The breakdown voltage and clamping voltage of TVS are both greater than the allowable voltage of the differential line. Can it still play a protective role? 】 Figure 2 Red box, 3.3V is the differential...

"The voltage that causes damage is higher than 3.3V."

I see. In this usage, the breakdown voltage VBR and clamping voltage VC of TVS must be less than the maximum allowable voltage of the rear-stage circuit, right? Thank you, senior!

maychang

xiaxingxing posted on 2022-3-19 13:57 "The voltage value that causes damage is higher than 3.3V." Understand, in this usage, the breakdown voltage VBR of TVS and the clamping voltage VC are...

"For this usage, the breakdown voltage VBR and clamping voltage VC of the TVS must be lower than the maximum allowable voltage of the back-end circuit, right?"

Generally speaking, it should be like this.

langtuodianzi

The maximum clamping voltage of the TVS device is not greater than the maximum safe voltage of the circuit.