[introduction]To prevent ESD (electrostatic discharge) cause electronic equipment malfunction or trouble, need is adopted proper antistatic measure. To circuit application, use normally stick outfit component directly, if did not choose appropriate antistatic fittings, the circuit signal during moving normally can be disturbed, include all sorts of having among them high speed and the communication circuitry of the signal that need branch, for instance the car carries communication CAN (controller local area network) , the car carries aether net to wait. Electrostatic discharge can cause tremendous effect to afore-mentioned circuitry normally, bring about communication quality possibly to become poor not only, serious when still can affect EMC performance.

To prevent ESD (electrostatic discharge) cause electronic equipment malfunction or trouble, need is adopted proper antistatic measure. To circuit application, use normally stick outfit component directly, if did not choose appropriate antistatic fittings, the circuit signal during moving normally can be disturbed, include all sorts of having among them high speed and the communication circuitry of the signal that need branch, for instance the car carries communication CAN (controller local area network) , the car carries aether net to wait. Electrostatic discharge can cause tremendous effect to afore-mentioned circuitry normally, bring about communication quality possibly to become poor not only, serious when still can affect EMC performance.

The article introduced improper antistatic the solution of the real case that component can drop EMC function and TDK.

Foreword – ESD precautionary measures and the influence to EMC function

ESD (electrostatic discharge) can cause electronic equipment malfunction or trouble, because this need is adopted appropriate antistatic measure. Use normally pressure quick resistor antistatic component will prevent electrostatic, and the goal line that is being protected component installation, for instance integrated circuit (IC) and ground wire (between GND) , if pursue,1 is shown. ESD protects component to aim to should bring to bear on to its changeover is low resistance form when the tall voltage such as ESD and bring ESD effectively to GND, protect protective IC or similar line thereby. Go up to stick outfit component directly normally in view of circuit, if choice of ESD protection element is undeserved, although carry the circuit signal between date of departure also can be affected normally, include all sorts of having among them high speed and the communication circuitry of the signal that need branch, for instance the car carries communication CAN (controller local area network) , the car carries aether net to wait. Electrostatic discharge can cause tremendous effect to afore-mentioned circuitry normally, bring about communication quality possibly to become poor not only, serious when still can affect EMC performance.

Graph 1: Use ESD protects the circuit give a demonstration when component

Real case

If preamble place is narrated, use improper ESD to protect component to be able to reduce signal quality and EMC performance. In the circuitry of the signal that need branch that if the graph is shown 2 times,is in especially, tall n and low n side used ESD to protect component. Right now, the electrostatic capacity difference of the ESD protection cell that uses in respective circuitry is met reduce the impedance symmetry between every circuitry, reduce mode to change character. In addition, mode changes character to become poor to may reduce EMC performance again.

Later development is based on evaluate data actually, introduced ESD to protect component to conduct EMI to experiment to mixing mode S parameter and CAN communication (150 Ω method) influence.

Graph 2: The capacitance between the installation position of element of protection of the ESD in circuitry of the signal that need branch and circuitry is poor

Mode changes character (Ssd12)

Graph 3 change character to measure mode actually (the assessment after Ssd12) result. The mode here changes character to be not the 4 port that normally the circumstance leaves to survey a system, be like the 3 port pattern that the graph shows 4 times to change character to evaluate a system however. As identical as 4 port, 3 port also can be used evaluate mode to change character. Among them x-axis states mode changes character (Ssd12) , cross axle expresses frequency. The data in the graph is the electrostatic capacity difference between line of ESD protection cell. The numerical value of Ssd12 is greater, character is wronger; Namely numerical value is greater, have more noise (in all model) changeover is communication signal composition (wrong standard) , vice versa. (detailed sees an appendix)
By the graph knowable, the static capacitance between line of ESD protection cell (Δ C) is bigger, ssd12 is poorer.

As reference, line out is returned in the graph of CAN in all the model clutchs streamline to encircle (CMC) the Ssd12 in standard IEC62228-3 limits a line. When 2.7pF of Δ C ≥ , will not satisfy the requirement of line of standard of Class Ⅰ .

From this knowable, Δ C is bigger, actual mode changes character to jump over difference.

Graph 3: Mode changes character (Ssd12)

Graph 4: The assessment that 3 port measure circuit

Conduct EMI to experiment (150 Ω method)

Next we conduct the introduction EMI to experiment (150 Ω method) result. In experiment of this give typical examples, after ESD protects component to affect mode to change character, the real property of EMC also was reduced.

Conducting EMI to experiment is one kind checks receiver to survey the test that noise conducts on line directly through EMI. In this test, evaluate board use CAN, if pursue,evaluate circuit 5 (conduct what EMI experiments to evaluate circuit to pursue) .

When evaluating ESD to protect component, need uses general CAN to press quick the array of the CAN2 syncretic of resistor and TDK is pressed quick resistor (AVRH16A2C270KT200NA8) . This AVRH16A2C270KT200NA8 uses two single track to press quick resistor closes 2 for of one enclose a form, only individual stick piece pressure quick resistor can protect a pair of line that need branch. 2 syncretic form is had can command the advantage such as difference of the capacity between circuit, will look with respect to the result, use than single track pressure quick resistor has better mode to change character.

Graph 5: Conduct EMI experiment to evaluate circuit

If the graph is shown 6 times,evaluate a result actually.

X-axis shows noise rate, cross axle expresses frequency. The electrostatic capacity difference between circuitry of orange data presentation is 13pF(Δ C=13pF) , right now individual pressure quick the catalog norms value in resistor is the poorest; Blue data presentation, although AVRH16A2C270KT200NA8 is in below circumstance of the biggest tolerance, the tolerance value between circuit is 1pF (Δ C=1pF) as reference, line out is returned in the graph the Class in IEC61967-4 the standard line of Ⅲ .

Individual pressure quick resistor crosses standard line to arrive from low frequency high frequency, and array pressure quick resistor maintains in standard line less than. Overall and character, the noise of array rheostat is controlled in lesser level.

Accordingly, should press quick when resistor does not work, poorer mode changes character to may reduce the EMC character below stable state condition.

Graph 6: Conduct EMI test result (odd piece pressure quick resistor and array stick piece pressure quick resistor AVRH series)

Conclusion – the ESD with right choice protects component (stick piece pressure quick resistor) have important sense

The article introduced improper ESD to protect component to be able to affect mode to change character, and also confirmed this one phenomenon through EMC experiment.

Experiment discovery, ESD protection element can prevent electrostatic, dan Rexuan incorrect, will cause undesirable effect to EMC function. Especially in recent years, the mode changeover character that the car holds communication line suffers fully take seriously, ESD protects component to also should have good mode to change character.

TDK car carries communication to press quick resistor considered ESD character not only on the design, still considered mode to change character. Because of this and press commonly quick resistor photograph is compared, be opposite in use process of EMC function reduce effect lesser also.

If if have any doubt,protect component to ESD, the welcome seeks advice at any time.

The model in clicking next watches can examine product detailed information.

Express 1: Be aimed at the AVRH16A2C270KT200NA8 norms watch of CAN FD

Express 2: Stick in the light of what the car carries Ethernet piece pressure quick resistor norms watch

Article origin: TDK

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