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Old Jun 19, 2005, 05:25 AM
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Hastings, New Zealand
Joined Jan 2001
5,217 Posts
It is possible to use a non pre-driver IC with external FETs. Connect a resistor from each motor phase to the supply, and another to ground. Then you can detect three voltage levels using two comparators, one per output FET. This requires 6 comparators and lots of resistors, so is probably more complex than using a pre-driver IC.

I chose the NJM2624 pre-driver for it's simplicity, availability and low cost (just $0.90 each at Mouser Electronics). One thing to watch with this chip is that although it can work down to 4.5V, its outputs can only go up to 1.5V below the supply voltage. Therefore at least a 6V supply may be needed to drive logic-level MOSFETs.

My circuit makes a stock CDROM motor act like a brushed DC motor, which can then be driven by a normal brushed ESC. The breadboard prototype worked very well, so I am now working on a surface mount version. The output switches will be SI4542DY dual N&P MOSFETs, for a total of only 24 parts on the PCB.
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Last edited by Bruce Abbott; Jun 19, 2005 at 05:32 AM.
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