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Replacement for HexSense FETSs

Discussion in 'Electronic Components' started by Roger Hamlett, May 22, 2007.

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  1. Hi,
    In the past, for some switching assemblies, I have on occasion taken
    advantage of the IR HexSense FET's. Big advantages at moderate currents of
    not needing an external sense resistor, at the 'cost' of needing an op-amp
    to generate a reasonably accurate current sense result, some drift on the
    high current units, and care needed in the software to 'tweak' for
    temperature effects. Typically using the IRCP250, at perhaps 20A.
    Now looking at redesigning a board I made some time ago, using these, and
    find that they are shown as 'Divested', by IR. They are available at
    present, but are obviously not the way to go for a new design.
    I found myself wondering what is being used to replace these?....

    Best Wishes
  2. Ray King

    Ray King Guest

    The hex since can be replaced by using the standard IRFP250 and a parallel
    fet of higher voltage such as the IRFU420 with a 100 ohm resistor in the
    source. Connect both drains together and connect both gates together. The
    current signal is taken at the connection of the 100 ohm resistor and
    IRFU420. The other end of the 100 ohm resistor is connected to the source of
    the IRFP250. Also the fancy negative supply is not needed with this
    connection because there is no concern about the signal current being
    diverted in the silicon of the IRCP250. It also is more accurate with no
    distortion at higher currents.
  3. Thanks.
    What suprises me, is that nobody seems to integrate such a solution
    though, the 'dual fet' solution, will be rather bulkier (there are already
    eight FET's along the heatsink, and while only four need current sensing,
    it may get a bit 'tight'... :)
    Have to find something other than the IRFU420 though. These too are
    Oh well, a 'redesigning I will go'!.

    Best Wishes
  4. I do not know the specific situation with this part, but just the
    fact that it is "divested" does not necessarily mean that you will not
    be able to get it in the future. Semiconductor companies have been
    selling product lines and splitting companies in the last few years.
    National Semiconductor, Motorola, HP, and others have done this over
    the last few years. It is just a matter of whether whoever ends up
    with the rights to your part chooses to produce it. I have been in
    several situations where I thought a key part was not going to be
    available due to this practice, but so far I have always been able to
    find it from some successor or partner of the original. (I am watching
    this particular situation myself as I use a number of IR parts.)
  5. OK. Yes, I understand this practice (met it a lot, with TI parts in the
    past). The problem (of course), is that you have to 'assume the worst',
    unless the new manufacturer is already in place...

    Best Wishes
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