ESD diode principle:
The ESD electrostatic protection diode is connected in parallel to the circuit. When the circuit works normally, it is in the cut-off state (high resistance state), and does not affect the normal operation of the circuit. When the circuit has an abnormal over-voltage and reaches its breakdown voltage, it quickly changes from a high resistance state to a low resistance state, providing a low impedance conduction path for the transient current, and clamping the abnormal high voltage to a safe level, thus protecting the protected IC or circuit; when the abnormal over-voltage disappears, it recovers to a high resistance state, and the circuit works normally.
The characteristics of the discharge signal during ESD testing are:
The test diagram and test results after adding the ESD diode are shown in the following figure:
Test sample (diode) is connected in parallel to the circuit.
It can be seen that the overvoltage peak has a significant drop within 50ns.
The technical parameters of this example device are as follows:
Features:
1.Lead free type.
2.Compact size for
3.Insulator over coat keeps excellent low and stableleakage current.
4.Quick response time(<1ns).
5.Low Clamping Voltage.
6.Meet IEC 61000-4-2 standard.--Contact discharge mode:typical ±15kv--Air discharge mode:typical ±20kv
Application for Mother Board,Notebook, cellularPhone,PDA,handheld device,DSC,DV,Scanner,andSet-Top Box etc.
About selection:
ESD electrostatic diode selection guide
1. The cut-off voltage of the ESD electrostatic diode should be greater than the highest working voltage in the circuit;
2. The selection of IPP and VC, the maximum clamping voltage, should be based on the possible maximum surge current on the line to select a suitable IPP model. It should be noted that at this time VC should be less than the maximum peak voltage that the protected chip can withstand;
3. When used for signal transmission circuit protection, be sure to pay attention to the frequency or transmission rate of the transmitted signal. When the signal frequency or transmission rate is high, low-capacitance series ESD electrostatic diodes should be selected;
4. Choose a suitable package according to the circuit design layout and the number of protected lines. The size of ESD packaging can reflect the level of protection of the device to a certain extent. Generally, the larger the package, the larger the ESD chip area that can be accommodated, and the higher the level of protection, and vice versa.
ESD electrostatic diode parameter explanation
? VRWM: Reverse cut-off voltage, in layman's terms, is the maximum working voltage that ESD allows to apply. Under this voltage, ESD is in a cut-off state. At this time, ESD's leakage current is very small, a few microamps or even lower.
? VBR: Breakdown voltage, breakdown voltage is the voltage at which ESD starts to operate (avalanche breakdown), generally measured under a specified current, usually measured under a current of 1mA.
? IR: Reverse leakage current, that is, ESD's leakage current measured when VRWM voltage is applied across ESD.
? IPP: Peak pulse current, generally measured with an 8/20μs waveform.
? VC: Clamp voltage, measured at a given size of IPP across ESD. Most ESD products have a positive relationship between VC and VBR and IPP.
? C J: Junction capacitance, ESD's junction capacitance is related to ESD's chip area and working voltage. For ESD products with the same voltage, the larger the chip area, the larger the junction capacitance; for ESD with the same chip area, the higher the working voltage, the lower the junction capacitance.
ESD electrostatic diode selection matters
1)ESD is generally used for electrostatic protection of various communication ports. In some high-speed data lines, such as USB3.0, HDMI, IEEE1394 and other interfaces, ESD electrostatic protection diodes should choose small junction capacitance as much as possible to avoid affecting communication quality;
2)ESD has unidirectional (A) and bidirectional (C) points. Choose according to the working signal. Unipolar signals can choose unidirectional or bidirectional ESDs. Bipolar signals must choose bidirectional ESDs;
3)What specific model of ESD electrostatic diode is used for electrostatic protection still needs to be selected under the guidance of a professional electronic engineer.
Comments
participate in discussions
Por favor faça login ? to participate in the comments
New customer Start here.