Please help me find the schematic diagram, thank you very much

shijizai

Please help me find the schematic diagram, thank you very much [Copy link]

 

Solve the circuit principle in the figure.

The whole circuit is an esd protection circuit.

If the input voltage at 1 is a positive pulse and is greater than the reverse working voltage, D2 will be turned on to short-circuit the large voltage, and the voltage of the entire circuit will be clamped at the clamping voltage to protect the circuit.

If the input voltage at 1 is a negative pulse and is greater than the reverse working voltage, D1 will be turned on to short-circuit the large voltage, and the voltage of the entire circuit will be clamped at the clamping voltage to protect the circuit.

D1 and D2 are NPN and PNP respectively

question,

1. Is what I said above correct?

2.What is D9 and what role does it play in this circuit?

topwon

D9 is a TVS diode that suppresses and clamps the transient high voltage of static electricity. Together with the 8 steering diodes D1 to D8, it forms an ESD protection array.

qwqwqw2088

There is a special IC for ESD electrostatic protection, which has a diode array arrangement inside.
SRV05-4 is similar to the picture of the original poster.

topwon

If the input voltage at 1 is a positive pulse and is greater than the sum of the forward conduction voltage Vf of D1 and the voltage Vcc of pin 3, D1 will be turned on to short-circuit pin 1 and pin 3, and the voltage Vcc of pin 3 will be clamped at the clamping voltage by D9, protecting the circuit.

If the input voltage at pin 1 is a negative pulse and is greater than the forward conduction voltage Vf of D2, D2 will conduct and short-circuit pin 1 and GND, and the pin 1 voltage will be clamped at GND-Vf, protecting the circuit.

topwon

D1~D8 are all diodes instead of transistors, and have only one PN junction, so there should be no distinction between NPN and PNP.

shijizai

topwon posted on 2019-9-4 14:57 D1~D8 are all diodes instead of transistors, with only one PN junction, so there should be no distinction between NPN and PNP.

Many thanks

shijizai

topwon posted on 2019-9-4 14:44 D9 is a TVS diode that suppresses and clamps the static instantaneous high voltage. Together with the 8 steering diodes D1~D8, it forms an ESD protection array.

So do the functions of the TVS diode and the ESD protection circuit overlap? Can only one of them be used?

topwon

Shijizai posted on 2019-9-5 09:15 So do the functions of the TVS diode and the ESD protection circuit overlap? Can only one of the two be used?

TVS is the abbreviation of transient voltage suppressor. Because of its fast reaction speed, its role here is ESD protection. D9 is the core of the entire protection tube array.

Similar to this are TVS tubes used for lightning protection. The principle is similar, but because the energy that needs to be absorbed is greater, the size will also be larger (the energy of static electricity is small, and generally if a TVS tube is used alone, a 0402 or 0603 package is sufficient, while a TVS for lightning protection generally requires a package size such as SMB).

In addition, when selecting, please note that TVS tubes also have unidirectional and bidirectional protection.

shijizai

topwon published on 2019-9-5 09:46 TVS is the abbreviation of transient voltage suppressor. Because of its fast reaction speed, its role here is ESD protection. D9 is the core of the entire protection tube array...

Since the TVS tube itself can achieve ESD protection, what is the role of the ESD protection array in the above circuit?

shijizai

topwon published on 2019-9-5 09:46 TVS is the abbreviation of transient voltage suppressor. Because of its fast reaction speed, its role here is ESD protection. D9 is the core of the entire protection tube array...

If pin 3 of the circuit in the figure above is not connected, then if a large voltage enters pin 1, the current will not flow through D9, right?

topwon

Shijizai published on 2019-9-5 09:53 Since the TVS tube can achieve ESD protection by itself, what is the role of the ESD protection array in the above circuit?

D1~D8 are steering diodes, which are mainly used to isolate the normal signal voltage of pins 1, 2, 5, and 6, so that the four signals can share a TVS tube D9. At the same time, D2, 4, 6, and 8 can help clamp to GND-Vf when there is ESD negative voltage on the signal line, such as pin1->D2->GND. When the ESD voltage on the signal line is positive, it still needs to be clamped and turned on by D9 to drain to the ground. For example, pin1->D1->D9->GND.

shijizai

topwon posted on 2019-9-5 11:26 D1~D8 are steering diodes, whose main function is to isolate the normal signal voltage of pins 1, 2, 5, and 6, so that the four signals can share one TVS tube D9. ...

If D9 is removed here, the above path will still be connected, and the diode can still guide the interference to GND. I still don't understand the role of D9? Why add D9?

shijizai

qwqwqw2088 posted on 2019-9-4 14:54 There is a special IC for ESD electrostatic protection, which has a diode array arrangement inside. SRV05-4 is similar to the picture of the original poster

Well, yours is very useful. SRV05-4 explains it in more detail.

topwon

Shijizai posted on 2019-9-5 15:11 If D9 is removed here, the above path will still be connected, and the diode can still guide the interference to GND. I still don’t understand the role of D9? Why add D9? ...

If D9 is removed, the above path will still be open. Please mark this path and see.

shijizai

topwon posted on 2019-9-5 15:47 If D9 is removed, the above path will still be open-------mark this path and see

I understand. If the upper diode of D9 is not connected directly to GND, there will be no clamping effect. Thank you.

zhuyebb

Thank you for your selfless sharing and dedication

乘风云上

D9 is a TVS tube. Nowadays, integrated chips are basically used for electrostatic protection. Discrete components are rarely used. It is difficult to calculate and select the type. On the other hand, the design effect is not ideal.

generalcircuits

Study in a building

shijizai

[quote]Chengfengyun published on 2019-9-9 14:36 D9 is a TVS tube. Nowadays, integrated chips are basically used for electrostatic protection. Discrete components are rarely used. It is difficult to calculate and select them. On the one hand, it is difficult to calculate and select them. On the other ...

Well, this is the internal schematic of the chip