caseSolution
  • For the solution of electrostatic discharge problems

    For the solution of electrostatic discharge problems, according to the following twelve rules to (prioritize)
    1.PCB non insulated casing wire and other wire distance of at least 2.2 mm. This applies to all objects connected to the chassis ground, including trajectory.
    2 chassis wire length should not be more than five times its width.
    Metal objects 3 the circuit without insulation and the operator can touch to the PCB area or ungrounded separated by at least 2 cm.
    4 power line and ground wire or ranking on PCB and in the same layer, or placed adjacent to the two layer.
    5 the ground plane and ground wire must be connected to the network. In an arbitrary direction, at least 6 cm every connection a vertical line and horizontal line. Especially the double PCB plate, that is to say, the first layer PCB board layout can be ground level, and the second layer can be vertical ground, must be at least every 6 centimeters place a hole has been connected to both (of course, less than 6 cm in the local connection is better than the ground grid, ground plane.
    ) 6 of all signal lines must be in the ground plane edges or less than 13 mm above the ground. Wire can be distributed in the same layer signal line, also can be in the next layer. If the signal line length of 30 cm or more, it must be placed on a ground beside it, placed above the signal line or the adjacent surface of the ground can be.
    Across the bypass capacitor between the 7 power line and the ground wire, the distance between each other is not greater than 8 cm (so that each piece of integrated block may have multiple bypass capacitor is connected).
    8 mutual connection more components rely on together.
    All 9 components must be as close as possible to the I/O connector (Note: should meet third).
    The 10 part will spare all of PCB filled with ground (attention should be paid to every 6 centimeters place continuously to produce ground network).
    11 if possible, which will feed power line or signal line from the edge at the center of PCB board, and not from a corner out.
    12 for the signal line is particularly sensitive and long (30 cm or longer), should be at regular intervals and ground.
    Note: these design rules must be applied to all PCB in the system (such as main board and plug in the above board). For example, when the application of article second, a ground length including the motherboard and the daughter board and the length of all the earth.
  • Electromagnetic compatibility design of power meter and the solving methods

    Compared with the electric parameters of transmitter power industry monitoring instruments commonly used with the traditional, gradually to the intelligent, integrated, multi-functional direction, and in the electromagnetic compatibility requirements are also high performance (EMS and EMI test were related requirements). The designer how to choose appropriate EMC design, a decisive role on the success or failure of the product design. This paper discussed the design of electromagnetic compatibility of the power monitoring instrument.
    The standard interpretation of
    1 standard
    Combined with the general standard of heavy industrial products, electric power monitoring instrument for power to meet the needs of EMS, EMI and grade is shown in figure 1.

    2 standard interpretation Interference is usually divided into two kinds of interference and transient interference. Such as mobile phone, walkie talkie, radio signal to interference. Because the switch, motor braking power fluctuation caused by such interference, we called the transient interference. Contains the transient interference figure 1: surge SURGE, static ESD, electrical fast transient EFT/B, voltage dips, short interruptions and voltage variations include: DIPS; interference conduction sensitivity CS, RS sensitivity to radiation.
    Evaluation of the class A of the &ldquo &rdquo does not decrease; performance; namely, applying interference, no hardware damage, data reduction, no crashes, dropped frames or bit error rate is higher in the process of applying interference, as applied to the products without interference. Usually persistent disturbance evaluation grade are the evaluation grade. The transient interference for incidental, grid disturbance caused by time and reduce the time is not long, the performance, also is the evaluation grade B.
    3 EMS test items and interference analysis of
    (2) the static ESD: waveform rise time is 0.7 1ns, the pulse is a pulse width of dozens of NS, because of its peak voltage is in the range of thousands of volts, so the pulse also has a certain energy, to do protection in port. Due to the rising edge is very steep, so the high frequency harmonics carrying is very rich, up to 500MHz, so the static electricity in all exposed metal parts instrument (including the terminal screws, etc.) contact discharge or aperture (including opening, LED indicator of the various thermal and observation hole), or on the level of coupled plates respectively. And the vertical coupled plate indirect discharge, will form a high-frequency electric field in the discharge point of instantaneous, through the space interference on the circuit, the interference is the common mode interference. Therefore, the static design should pay attention to the protection and space port high frequency radiation of two aspects.
    (3) EFT/B: Electrical fast transient wave rising edge to 5ns, waveform into a number of periodic pulse string combination, very low energy. Properties and electrostatic interference is the same as the common mode interference path, including transmission also includes radiation.
    Conducted susceptibility of CS (4): the common mode interference, interference frequency band from 150KHz to 80MHz. In the project during the experiment, the interference signal source to instrument cable length and interference frequency band (30MHz) corresponding to the wavelength of the λ 1/4 is applied, the frequency modulation interference voltage exceeds 30MHz, due to the skin effect, the interference signal in space radiation mode (less than 30MHz, or in the main transmission interference).
    The radiation sensitivity of RS (5): the common mode interference, interference frequency band from 80MHz to 1GHz. Need to pay attention to, drag cable as a receiving antenna, electromagnetic interference for the far field.
  • Design of electrostatic discharge of PCB plate and the solutions

    In the design of PCB board, can be layered, proper layout and installation of anti ESD design and implementation of PCB. By adjusting the PCB layout, can be very good to prevent ESD. * multilayer PCB is used as far as possible, the double PCB, the ground plane and power plane, and closely spaced signal earth line spacing can reduce common mode impedance and inductance coupling, so as to achieve the double PCB 1/10 to 1/100. For the top and bottom surfaces are components, with a short connecting line.
    From the human body, the environment and internal electronic equipment for semiconductor chip precision electrostatic will cause damage, such as through the components inside the thin insulating layer; a gate MOSFET lesion and CMOS components; CMOS device triggers lock; short PN junction reverse biased; short road to biased PN junction; active devices within the melting welding wire or wire. In order to eliminate the electrostatic discharge (ESD) interference and damage to the electronic equipment, need to take a variety of technical means of prevention.
    In the design of PCB board, can be layered, proper layout and installation of anti ESD design and implementation of PCB. In the design process, through the forecast can be modified only to increase or decrease the vast majority of design components. By adjusting the PCB layout, can be very good to prevent ESD. The following are some of the common measure.
    * multilayer PCB is used as far as possible, the double PCB, the ground plane and power plane, and closely spaced signal earth line spacing can reduce common mode impedance and inductance coupling, so as to achieve the double PCB 1/10 to 1/100. As each signal layer are close to a power supply layer or ground layer. For the top and bottom surfaces are components, with a short connecting wire and a lot of filling high density PCB, can consider to use the inner line.
    * for a double PCB, by closely interwoven power and ground grid. Power line is close to the ground, between vertical and horizontal line or fill area, as much as possible to connect. The size of the grid side is less than or equal to 60mm, if possible, the grid size should be less than 13mm.
    * make sure that every circuit as compact as possible.
    As far as possible to all connectors are put aside.
    If possible, the introduction of the power line from the card and away from the central, to be directly influenced by ESD region.
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