Re: 300 mA from a microcontroller pin

In article <5OC3j.23514$j7.444022@xxxxxxxxxxxxxx>, toe@xxxxxxxxxxx
says...


I have a 14-pin PIC microcontroller, the 16F684 to be exact. Each pin
can be either 5 V, 0 V or high impedance, however they can only source or
sink 25 mA, but I need 300 mA (both sourced and sunk). Currently, I'm
using a setup consisting of an NPN and a PNP transistor in order to
provide more current, like so: http://img124.imageshack.us/img124/6215/
driverbeforegj7.jpg (the microcontroller is on the far left).

I've heard of things called "drivers" that can be used to boost the
current, whilst still being able to provide the three states of 5 V, 0 V
and high impedance. I've searched the web and come across things like the
ULN2003 the MAX15025, but I'm having difficulty finding what I want. It
seems that the ones that can provide enough current can only source
current, while the ones that can source and sink tend not to be able to
provide enough current.

Can someone please suggest a driver chip so that I can effectively
get 300 mA out of my microcontroller pins? Remember that I need the three
states.

Try searching for "half-bridge driver". These chips include both
a high-side driver and a low-side driver and are designed so
that you cannot inadvertently connect the +5V to ground.
You will probably need two pins for the control---one to enable
the driver and the other to set the output to +5V or to 0V.


Mark Borgerson


.

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