Non-inverting Driver Available

[lforbes]

Have just realized that the output driver chip (UNL2803A)that comes with the standard 18 pin project board inverts the output. Does anyone know of an equivalent chip (with same pinout) that does not invert?

I plan to use this board to drive four power MOSFETS in a H-bridge circuit so, with inverted outputs there will be a short circuit in the H-bridge for a short time on power up or reset i.e. all the MOSFETS will be on until the program can set the PIC outputs high.

 

[Rickharris]

Insert transistor to invert outputs. Only small currents are needed.

 

[evanh]

Look up the UDN range of transistor arrays.


Evan

 

[ljg]

You can still use your 2803A to drive your mosfets. Just Gang the output of one darlington to feed the input of the next(with a proper resistor). The result will be non-inveted.

I think a better solution, though is to use a 7407 buffer chip. Though it isn't pin compatible, it has the advantage that it s open collector and can sink higher voltages than the input without affecting the Picaxe pins. Since it is open collector, You use a pullup between the driver output and the MOSFET gate that is conected to motor power voltage. This will insure that the FET is fully on if your MOSFET isn't a logic level device.