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H-bridge motor driver layout

Discussion in 'Electronic Design' started by Mike V., Jul 14, 2004.

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  1. Mike V.

    Mike V. Guest

    On many half bridge driver ICs (e.g. international rectifier, ST,
    Intersil), you would use two of them, along with four MOSFETs to make
    an H-bridge configuration. They also give the layout guideline that
    says:

    "The motor driver IC's ground and the motor ground should all meet at
    ONE point." (Sort of like star grounding?)

    That rule is easy to abide by, especially if it is a 2-layer board.
    What about if my board is a four-layer board? Can I simply flood the
    whole area with a ground plane, and just drop every ground pin into
    the ground plane? Thus the driver IC would have 12vdc-15vdc as its
    Vcc, the motor can have 100Vdc, and they all share the same ground
    plane. Or am I going to have problems by simplifying the layout with a
    ground plane instead of following the "all meet at one point"
    guideline?

    Thanks,
    Mike
     
  2. Rich Grise

    Rich Grise Guest

    For that much difference, I'd really use two separate ground planes.
    You want to minimize the copper that has current returning from both
    loads, i.e.:

    +Vcc +Vdd
    ckt a ckt b
    ret ret
    | |
    +-----+-----+
    |
    [ Rg ]
    |
    supply ret.

    Rg is the copper area I'm talking about. The less copper the two
    have in common in their ground path, the less coupling you get.
     
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