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    pcb quiery

    cn anyone tel why the ground of pcb are broad

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    pcb quiery

    normally PCB ground traces are broad to protect the circuit from external interference.



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    pcb quiery

    is this is also the reason that their shld b less electron collision wit the atom of the material



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    Re: pcb quiery

    yea that's also an important reason since all currents will be returning from that path to the source.



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    pcb quiery

    The ground tracks must be broad in order to reduce the external noise interference and for the return path as well and in some high speed boards the ground tracks are also used to match the impedance of the signal tracks there are lot many uses by providing a good ground to the board the best practice is to fill the vacant places in the PCB with ground so that it will be tightly coupled with the signals and the power



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    Re: pcb quiery

    Quote Originally Posted by vijaya_narayana View Post
    The ground tracks must be broad in order to reduce the external noise interference and for the return path as well and in some high speed boards the ground tracks are also used to match the impedance of the signal tracks there are lot many uses by providing a good ground to the board the best practice is to fill the vacant places in the PCB with ground so that it will be tightly coupled with the signals and the power

    Dear Vijaya,

    Please suggest the rule of thumb for distance between ground pour and the traces.
    Is it frequency dependant?
    When ground poring becomes essential?



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    Re: pcb quiery

    In a practical sense, the more 'ground' the better; otherwise, wait until EMI testing and find out otherwise!

    I drew up and produced a board (needed to show a proof-of-concept at that stage) using a 'simple' Z80A uP (early 1990's time frame) and the 'ground' was really composed only of a .1" wide buss between and among the 5 or 6 other chips (incl PIO, CTC, EPROM, SRAM etc), and the design was noisy RF emissions-wise.

    The succeeding layout (2nd version) employed literal 'ground plane' to provide a termination for 'E field' emanating from the digital address and data lines as well provide a low impedance path for digital signals rather than only the .1" bus between ICs ... that design emanated much less RFI up to and past 30 MHz than the first layout ...

    Jim



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