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TQFP pin 21 for AGND versus GND
July 12, 2014
12:40 pm
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July 12, 2014
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Hi Jeremy!

I'm new to your site but I did download your Eagle library file thecustomgeek.lbr. Thanks so much for sharing!

Unfortunately I found a small error on your ATmega328 TQFP schematic; you show pin 5 as AGND, but that should be pin 21. To confirm, a search of Atmel datasheets show no such thing as 'AGND', but, if you search a datasheet for 'ADC Power', then the second instance shows a figure where pin 21 is connected to an 'Analog Ground Plane', making pin 21 the obvious AGND.

This difference would affect only noise-sensitive applications, where a user might want to make an analog ground plane to which pin 21 would be connected. I am unsure whether this impacts your really cool 'One Square Inch of Goodness'. TQFP users wishing to maintain separate digital ground and analog ground traces would want to be sure to connect to the correct pin. Reference http://electronics.stackexchan.....ound-plane.

Keep up the great work, and Thank You Again for sharing schematics, etc. Love your 'Math Required' confirmation rather than the standard 'try-to-figure-out-random-nonsense' onesCool.

- Bob

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