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    ground loop in an IC chip

    various circuits grounded on the same ground plane can cause voltage drops across the ground plane. These various voltage drops can create additional currents in the circuit lines, therefore causing round loop coupling in the various circuit. this phenomenon is always been discussed in PCB level. how about the various integrated circuits within a microchip? does ground looping occur? usually the ground of the circuits will be connected to a wide metal (ground plane), then it will rout to the bond pad. will it cause ground looping, cause most fo the circuits will share the same ground bus.

    •   Alt8th April 2005, 05:05

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    Re: ground loop in an IC chip

    In very big SOC the ground looping do happen. So it is advisable to have a tree structure for the same ie supply distribution and avoid loops



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    Re: ground loop in an IC chip

    You can even separate you supply rails into several internal pads. At the padring level, group all similar pads one aside the others, so that you can bond those pads to the same package terminal. This will add some inductance in series with each internal supply rail, reducing the noise induced on other supply lines.



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    Re: ground loop in an IC chip

    Quote Originally Posted by Apollo13
    In very big SOC the ground looping do happen. So it is advisable to have a tree structure for the same ie supply distribution and avoid loops
    i would like to know very big SOC is consider how big? is a 2mmx2mm chip consider big?



    •   Alt8th April 2005, 11:12

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    Re: ground loop in an IC chip

    How much is the transistor count, we are talking in this 2mmx2mm chip



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    Re: ground loop in an IC chip

    Rather than physical size alone, it also depends on the amount of current you are drawing and the accuracy levels you are trying to acheive..(a 1A chip has many more issues than a 1mA chip and a 16 bit resolution has many more issues than a 8 bit one).

    As was previously mentioned, you can have several gnd domains on the chip that are not connected (analog gnd , digital gnd) and you can connect them in the package or keep them separate all the way to the board.


    David Reynolds



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    Re: ground loop in an IC chip

    Quote Originally Posted by DReynolds
    Rather than physical size alone, it also depends on the amount of current you are drawing and the accuracy levels you are trying to acheive..(a 1A chip has many more issues than a 1mA chip and a 16 bit resolution has many more issues than a 8 bit one).

    As was previously mentioned, you can have several gnd domains on the chip that are not connected (analog gnd , digital gnd) and you can connect them in the package or keep them separate all the way to the board.


    David Reynolds
    the 2mmx2mm chip is drawing about 160mA-180mA of current. i did have several grounds on the chip like analog ground, digital ground. as for analog ground, since there are 4 channels in the chip, therefore we have 4 separate analog grounds. it is definitely helps to reduce noise coupling. does this good enough to prevent ground looping from happening?



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    Re: ground loop in an IC chip

    Ground lop would be formed, if the current going to ground doesnot leave the chip. But keep circulating in a loop. That would happen only if the path for ground current to move out of the chip has higher resistance than the one inside.
    If we avoid having loop structre for supply rail, it could be easily avoided.
    large number og gnd pins in parallel would decrease your inductance, that causes ground bounce. Also each ground pad has a limit to the current it can sink.



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    Re: ground loop in an IC chip

    signal can be prevented by large freq banks on the way of signal



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