Can I use a "Pre-FET" switch to drive loads directly?

Discussion in 'The Projects Forum' started by Beecher, Jun 15, 2009.

  1. Beecher

    Thread Starter New Member

    Jun 14, 2009
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    Fellow Travelers:

    My application requires controlling a set of six 12VDC solenoid valves that each pull a 500mA holding current. Logic control is supplied by a PIC microprocessor sending a +5V signal to trigger the valve. No more than two valves are drawing current at the same time.

    The current design uses individual IPS1051L low-side power MOSFETs to handle the switching. However, I'd like to eliminate these individual components in a new design to save space and assembly time. My first impression was to use a Darlington array to replace the IPS1051L's, but the beefiest Darlington I can source is 500mA max per channel so I'd be living on the edge.

    Instead, I'm considering using a TI TPIC46L series low-side "pre-FET" driver to switch the valves directly (datasheet here: http://focus.ti.com/lit/ds/symlink/tpic46l01.pdf).

    Although TI specs this chip for triggering external FETs it seems to have enough oomph to switch the valves directly. However, I'm skeptical that TI would call this a "pre-FET" driver if it could actually handle the kind of application I'm looking at.

    Am I missing something here? Does anybody see a problem with replacing the six IPS1051L's with one of these?

    Thanks in advance.
    Beecher.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    This chip is designed to drive FET transistors, thus you cannot use it to drive solenoids directly.
     
  3. Beecher

    Thread Starter New Member

    Jun 14, 2009
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    Thanks.

    Any particular reason why it would see a FET and another load differently?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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  5. Beecher

    Thread Starter New Member

    Jun 14, 2009
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    Thanks Sarge.

    Missed that one when I was digging around for a higher current Darlington. That should do the trick nicely.

    Much obliged.
     
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