Help ID MOSFET driver chip

May 23, 2011 3 Replies
R

I want to repair a speed controller for a brushless DC motor. The MOSFETs are burned out, and so is this little chip, which I believe is a dual driver for the MOSFETs.



Here's a picture:



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It is marked "IX" or "XI". That does not give me any clue.



Each driver drives two SI4442 and three SI4405 MOSFETs. The speed controller is controlled by an ATMEGA8.



I have an identical speed controller which is working OK, so I can take measurements from that if it helps.



I need to find out exactly what part this is, so I can try to find them or a suitable (pin compatible) replacement.


RoRo
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G

Could it be X1? that returns a few hits here:

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Unfortunately though these markings are not unique and it may not be any of those.

It may be easier to work out what it is from measurements than the markings.

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G

Index mark to left, so it's XI? Hmm X1? --> dual transistors pnp + npn is feasible for emitter follower gate driver?, see

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for several options

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R

That looks very promising. A twin transistor could well be used in this application.

I have now done some measurements. It seems the two transistors are interconnected somehow, so it is tricky to get some sensible readings. I have also tried to examine the connections on the board, but that's not easy, since the board has more than two layers, and uses buried vias as well. I'm quite sure, though, that one of the bases is connected through a 4.7k resistor to a pin on the microcontroller.

Thanks Gareth and Grant.

RoRo
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