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TC4427 Driver problems .... possible solution

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Trevor Smith
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2018/08/30 17:15:24 (permalink)
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TC4427 Driver problems .... possible solution

Hi All,
Hope I'm in the right forum here. 
Also, hope nobody's had a day like mine today, chasing TC4427 "failures" ........ but I might have a solution.
 
I'm using multiple TC4427 drivers to control many external linear actuators FORWARD/REVERSE.
The linear motors each need 12VDC power (6A fused on my PCB) and a signal ON=EXTEND, OFF=RETRACT.
They have internal relays, to drive the motor in each direction and stop automatically at each end.
The TC4427 can take 2 inputs from the PIC and drive 2x12V power outputs .... all in an 8 pin package....... lovely.
 
Simple ! ....... until the TC4427 start "failing".
 
During long "OUTPUTS-OFF" periods, individual TC4427's can suddenly latch-up and cannot be switched off by the PIC.
This is obviously due to transients, grounding problems, etc.
So, I've done loads of google-ing  about latch-ups, etc .... and I think I've found a work-around.
The TC4427's have not failed, they work fine when tried again in circuit.
 
The secret seems to be to "Flash" their inputs, from the PIC, about every 1 second.
Flashing them ON for about 50uS, then OFF again seems to keep them healthy throughout.
Clearly, the outputs being ON for only 50uS, is far too fast for the linear motor relays to react, so happy days.
 
Working well so far !
Hope this helps someone else.
Trevor
 
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9 Replies Related Threads

    Jim Nickerson
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    Re: TC4427 Driver problems .... possible solution 2018/08/30 17:25:27 (permalink)
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    Nice.
    Are you using the TC4427 and not the TC4427A ?
    #2
    Trevor Smith
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    Re: TC4427 Driver problems .... possible solution 2018/08/30 17:29:14 (permalink)
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    Update,
    Been "flashing" away for several hours now, with x24 linear actuators, periodically all sequenced, 1 through 24, to "EXTENDED" and then "RETRACTED" ...... no problems so far.
    #3
    Trevor Smith
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    Re: TC4427 Driver problems .... possible solution 2018/08/30 17:33:35 (permalink)
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    JANickerson
    Nice.
    Are you using the TC4427 and not the TC4427A ?

    Hi Jim,
    Just checked on RS, I bought TC4427CPA's.
    Is that significant ?
    Trevor
    #4
    Jim Nickerson
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    Re: TC4427 Driver problems .... possible solution 2018/08/30 17:36:06 (permalink)
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    I just noticed this note on the product page https://www.microchip.com...27#additional-features

    The A says less prone to latch up. 

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    #5
    Trevor Smith
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    Re: TC4427 Driver problems .... possible solution 2018/08/30 17:43:48 (permalink)
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    P.S. was desperate to fix this ASAP, as it's a panic project.
    I've got projects out there driving very large 12V 80A DC motors, using TC4427's driving multiple IRLB8743 mosfets, but not only about x100 made so far, in 3 years.
    This new project will be higher volumes .... and uses x12 TC4427's on each PCB ...... crunch time !
    Trevor
    #6
    Trevor Smith
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    Re: TC4427 Driver problems .... possible solution 2018/08/30 17:54:48 (permalink)
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    JANickerson
    I just noticed this note on the product page https://www.microchip.com...27#additional-features
    The A says less prone to latch up.

    Thanks Jim.
    Haven't found specifically "TC4427A" anywhere but MC, so may have to buy direct.
    However, if my PCB is still happy all day tomorrow again, maybe I'm ok.
    Trevor
    #7
    Jim Nickerson
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    Re: TC4427 Driver problems .... possible solution 2018/08/30 17:58:42 (permalink)
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    Mouser and  DigiKey both claim to have them ( no doubt in US stock ).
    #8
    Trevor Smith
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    Re: TC4427 Driver problems .... possible solution 2018/08/30 18:09:24 (permalink)
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    Thanks Jim,
    I'll take look.
    Buying anything just lately is a nightmare.
    I run a small electronics business from home, with my daughters building systems.
    I buy thousands of components a month, but will soon need someone just to sort out who's got stuff in stock !
    I don't really have time to design stuff anymore !!
    Trevor
    #9
    Trevor Smith
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    Re: TC4427 Driver problems .... possible solution 2018/08/30 18:16:17 (permalink)
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    Update .... system has done 10 hours now without problems.
    I added an "output monitor circuit" on a bread-board, to give a common return from all TC4427 outputs and programmed the PIC to light an LED, if it sees any TC4427 output ON when it shouldn't be.
    Nothing bad so far.
     
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