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Author Topic: disadvantages to not wiring up all the power pins on a 328p?  (Read 545 times)
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I guess it it good practice to wire both the grounds and 5v signals on this type of IC, but I have made simple projects before and only connected 5v and gnd on one side of the chip, what are the potential issues with this? I guess they are internally connected so I can't really see the point in connecting them all unless you will be drawing any power through it?

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Most do see the sense in it besides it being a factory recommendation
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So are you likely to come up against issues if you don't do it?

Thanks
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I guess it it good practice to wire both the grounds and 5v signals on this type of IC, but I have made simple projects before and only connected 5v and gnd on one side of the chip, what are the potential issues with this? I guess they are internally connected so I can't really see the point in connecting them all unless you will be drawing any power through it?

Try reading the datasheet.

a) Each VCC/GND pin can only handle 200mA. You'll do damage if you only connect one power supply pin then load up the chip I/O pins.

b) The pins may be connected internally but each VCC/GND pin feeds a different set of I/O pins. If you only connect one power pin then load up the "wrong" I/O pins then again, you'll doing damage.

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Thanks, I'll bear that in mind for future projects. Luckily all of the projects that I have made and only connected one side are still working smiley
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a) Each VCC/GND pin can only handle 200mA. You'll do damage if you only connect one power supply pin then load up the chip I/O pins.

b) The pins may be connected internally but each VCC/GND pin feeds a different set of I/O pins. If you only connect one power pin then load up the "wrong" I/O pins then again, you'll doing damage.

I've often wondered about this question myself, that's a useful explanation, thanks.
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More importantly, if you connect Vcc to the supply but don't connect Avcc, then I have heard that the chip sometimes doesn't work correctly, even if you are not using the ADC.
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I guess it it good practice to wire both the grounds and 5v signals on this type of IC, but I have made simple projects before and only connected 5v and gnd on one side of the chip, what are the potential issues with this? I guess they are internally connected so I can't really see the point in connecting them all unless you will be drawing any power through it?


Wire them all, decouple them all.  The decoupling is the important point, the multiple leads means
a lower inductance path to the first decoupling capacitor, this is why multiple power and ground pins are needed.
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remember that the chip inside the IC is also a circuit with it's connection and grounding requirements.
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Every pin that a manufacturer uses costs him. It's a good assumption that if fewer power and ground pins would work satisfactorily he would use fewer power and ground pins, don't ya think?
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