Comparison between bav99 and TVs in electrostatic Application

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Many of our engineers like to use bav99 for Electrostatic protection. They think that bav99 can be completely static. In fact, this idea is wrong,

As we know, bav99 is a diode that does not have the fast response and low clamping voltage characteristics of TVs. For this reason, we take the TVs uclamp0501p/uclamp3301p/uclamp2501t of semtech for comparative analysis.

1bav99 electrostatic Application

In electrostatic applications, for bav99, the electrostatic Application diagram is as follows:

• When positive static electricity occurs, D2 works but D1 does not, therefore, the clamp voltage is 5 V plus positive voltage of D2 so the clamping voltage at protected pin will be + 5 V plus D2's forward voltage.

• When negative static electricity occurs, D1 works but D2 does not, so this clamp voltage is the forward voltage of D1.

2. electrostatic Test

• + 8kv contact ESD Testing

From the test results, we found that:

1. semtech uclamp0501p, uclamp3301p and uclamp2501t have lower clamping voltage than bav99

2. From the bav99 clamp voltage waveform, it can be seen that it is very wide, so it has greater energy from D2 into the 5 V power supply, so it is easier to damage the protected circuit and power supply

•-8kv contact ESD Testing

At-8kv contact discharge:

1. semtech uclamp0501p, uclamp3301p and uclamp2501t have lower clamping voltage than bav99

• At contact discharge range from 200 V to 8000 V, uclamp0501p, uclamp3301p and uclamp2501t also exhibit the lower clamping voltage vs. bav99.

At contact discharge range from + 200 V to + 8000 V

All of data above are taken with a 10x attenuator.

From the above test results, we found that semtech uclamp0501p, uclamp3301p and uclamp2501t have lower clamping voltage and energy than bav99.

　　
Conclusion:

Therefore, in electrostatic applications, semtech uclamp0501p, uclamp3301p, and uclamp2501t have lower clamping voltage than bav99 when static electricity occurs,

It can be seen from the positive electrostatic waveform of bav99 that it has greater energy, so it is easier to damage the protected circuit and exert large energy on the power supply, while TVs does not. therefore, semtech TVs provides more reliable and secure Electrostatic protection performance.

 

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The VGA part on the computer motherboard is usually bav99 in RGB.

We know that bav99 is followed by two diodes, one end is connected to the power supply and the other end is grounded.

I just don't understand, when the positive voltage comes, whether it is directed to the ground or pulled to the power supply part, the negative is also.

 

This is a protection measure for your output end. The high voltage will not exceed the positive voltage, and the low voltage will not exceed the ground.

 

No, it protects your chips and prevents external attacks.

 

Sorry, this is not a device for ESD protection. It is used to prevent overvoltage protection or ringing. It is estimated that his activation time is not enough for ESD. If you want to perform ESD, You need to select other components.

------------------------------------------------ I think.

 

From peak forward Surge Current (Note 1) @ T <1.0 μs IFSM 2.0 A, we can see that it is anti-surge.

 

It is anti-ESD (location-related ). Placed on the edge of the IC. Prevents voltage and negative pulses from over-power supply.

 

We use this device to place it in the interface circuit of the Board socket to suppress the conduction disturbance resistance.

Using an oscilloscope, we can see that after common-mode interference is coupled, a bidirectional high voltage will be generated on the signal line.

With bav99, the voltage range will be clamped at the interface.

However, it can be seen that, with external interference, the power supply for Positive Pressure clamping will generate great noise. Similarly, the ground for negative pressure clamping will generate great noise.

Therefore, it is recommended that this type of device be used together with the interface impedance filtering.

 

The main function is ESD protection. When several K of static electricity is imported from the input end, the diode is reverse-Penetrated, and the charge is quickly pushed to the ground or power supply. Most of the static electricity is put to the power supply.

 

Bav99 is a bidirectional diode.

I understand two roles:

1. limit;

2. Protection (because the back stage is the output end, if the back stage terminal is mistakenly inserted from the outside, for example, when the power supply is set, it plays a protection role .)

1. c458, c459, and l65 are combined into two filters, the second-order low-pass filter, and the most common circuit structure of CVBS output. It should be noted that CVBS and smaller than 6 MHz are useful signals. CVBS signal definition is very strict, you can look at the relevant radio and television standards.
2. The two transistors are shot-and-Zoomed, the voltage is basically maintained, and the current is amplified. It mainly improves the drive capability. Because the CVBS signal amplitude is fixed to 0.7Vpp, and the synchronization header is 1vpp.
3. Both diodes and bav99 are used for interface protection. Bav99 capacitance 1.5pf, 1n4148 capacitance typical value is 4pf, VRR is 75 V-100 V. The two are basically the same as bav99.

 

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Circuit details:

 

Bav99 is designed for the purpose of ESD. It is afraid that the signal line is vulnerable to ESD Interference or discharge damage the circuit. Because these interfaces are interconnected with each other, it is afraid that the received signal has large static electricity. "~ 9 R % W. @ & I $ B # f * P
1. When a positive static electricity is added to this signal, the ground diode is not turned on, the power supply diode is turned on, and the potential clamp is at a voltage drop of 5 + tubes (O + W, r6 N2 K
2. When a negative static electricity is added to this signal, the diode connected to the power supply is not turned on, and the ground diode is turned on, potential clamp in negative tube pressure drop 5 I/\ 1 H "J0 E: ['|
This voltage is generally the level voltage 0 C1 o $ p W (F + B3 L
Bav99 is a tvstube. Here, it can be replaced by a TVs static protection tube, and the tvstube has better performance. -T3 \) P9 T # T7 \ 0 h
The resistance r425 acts as an impedance matching.