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Common Cathode or Common Anode

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waqas_here

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common anode and cathode

Hey i made a 4 digit 7 segment based display using AVR working fine. I have a reservation in mind regarding power consumption of AVR. Currently i m using common cathode display (multiplexed by NPN transistor) which turns on segment when AVR's Port output is high. So it must b consuming more from microcontroller. On contrary if i use common Anode the on current for the segments will b drawn from supply rather than controller.
Wat u guyz think abt it.
 

avr common cathode

Obviously, there can't be a difference in overall current consumption. If the port pin has similar voltage drop with VDD or GND switching (most likely with modern CMOS IC), both variants are equivalent. TTL compatible ports may have stronger GND switching drivers, in this case common anode would be preferrable if high drive capability is required. You may want to consult your uP's datasheet to check the details.
 

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    waqas_here

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common cathode and common anode difference

I think waqas_here is more clearly worried regarding the maximum current possible from his microcontroller & not for the overall circuit's current consumption. He is worried if the controller blows up. Completely satisfied with FvM, read the current being drawn from i/o's of controller & then read the datasheet see if it's in limit or not?
you can add buffer in between if space & money is not a constraint.

All reagrds to Electronics.
 

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    waqas_here

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