Need to power mcu2 from mcu2 via pin.

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I have a device that has some type of IC in it, this is unknown for the moment.  I can power this IC up with usb power but I need to use a pin from my atmega328 portd.  I'm not sure what the issue is but guessing not a high  enough voltage or not enough power from the pin. I tried to bring two pins hi and tie them together with no luck.  I also added a cap with no success. I'm not sure there is anything that can be done without adding additional components. The reason I need to use a pin is that I also need this wire switchable. In one application I need to pulse the wire and the other supply an IC. Any ideas?

 

 

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Measure how much current the ic draws at 5V. If its more than 40ma, you need a mosfet buffer.

Imagecraft compiler user

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As Bob noted, you need to know how much current the device draws.

 

The I/O pins on the AVR's tend to drop their voltage as the current load increases.

On many (all?) data sheets there is a graph of the I/O pin output voltage as a function of the current being drawn.

 

Google High Side Driver for info on using a PFet driving an NFet to power the device, controlled by the uC.

 

JC

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Thx guys, turned out to be something stupid on my part.  I didn't realize the pin was going lo outside of my code. So it essentially was oscillating every 10 ms. Once I removed that oscillation it powers the IC just fine. Nice tip about the buffer, that would do the trick if I maxed out my current, good to know.

 

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S_K_U_N_X wrote:
I didn't realize the pin was going lo outside of my code.

Now >>that<< is a cute trick.  Better call Ghostbusters...

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.