Microchip, SOT235 in small circuit.. Hard to identify

Discussion in 'General Electronics Chat' started by Tuffe, Mar 9, 2011.

  1. Tuffe

    Thread Starter New Member

    Mar 9, 2011
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    Hello everybody [​IMG]
    Several Leds, inside a series of "professional" RGB - DMX controlled Led-light fixtures, stopped to function, and the supplier refuses to give me any technical information at all.
    I have identified a small component who visually have all signs of breakdown, but even i have all the numbers on top of it, i am not able to identify it.
    As i have no documentation, i do not even know the function of the circuit, but i guess it supports the dimming..
    The circuit contains of this chip, plus 3 smd resistors, one capacitor, one schottky SS12, and one coil, marked as 470.
    I have added picture of both the small circuit, and the component in close up, and I highly appreciate every thoughts about what this might be.. The marking seems to be: 318 T885A... SOT23−5

    Best regards.
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Based on the markings - the only thing I'm sure of is the manufacturing country is Taiwan and it was built in the 31st week of 2008.

    The other markings are probably vendor specific and have been changed from manufacturing standards to prevent the very thing you are trying to do. They want you to throw it away and buy a whole new unit.
     
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  4. Tuffe

    Thread Starter New Member

    Mar 9, 2011
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    Thanx for all info!! ... I am afraid you are right about that, but i hope not... They want us to treat everything as disposable... and its really too bad.. So i will try some more, to see if anyone else can give me a clue :D
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    That should be 470uH, not mH.
     
  6. Markd77

    Senior Member

    Sep 7, 2009
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    It could be a MOSFET, bipolar transistor, or even a current sensor based on the components around it. Do any of the traces connected to it look like they are for heatsinking - ie. not connected to anything?
     
  7. Tuffe

    Thread Starter New Member

    Mar 9, 2011
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    I will try to trace the legs, to see what i can find out..
     
  8. tom66

    Senior Member

    May 9, 2009
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    Given the 47µH inductor and low voltage diode (40V Schottky) I'd say it's a buck converter. Could you give a go at tracing the traces coming out of the chip?

    I think I have seen a similar chip before. There is a fairly standard pin out for 5 pin buck converters. Even if you can't find the exact device an equivalent may do the job with some reading of datasheets.

    47µH suggests either a low operating frequency <1MHz or a low output current (or both.)
     
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