Do the XMEGA Power pins belong to the port next to it?

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In the XMEGA controllers the pinout is really nice, all the ports are placed counter clockwise around the package. What I would like to know is if the power pins next to the ports actually belong to that port...

 

(XMEGA 128A1U for example)

 

Port C is on Pin15-22

Is GND Pin 13 / VCC Pin 14 related to PORT C or they are just put there for whatever reason?

 

Thanks for helping!

Cheers

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Only Microchip can answer that question for you.

The Xmega is a relatively complex chip, and how the dye is laid out internally is sometimes non-intuitive, and not public knowledge.

 

So, have to ask, why the interest?

 

ALL Vcc pins must be connected to Vcc, even if you are not using a given port.

ALL Ground pins must be connected to Ground.

The AVcc pin must be connected to Vcc, although this can be through an LC filter, is desired.

 

Likewise, ALL of the pairs of power pins, Vcc/Gnd, and AVcc/Gnd must have a by-pass cap, typically 0.1 uF, across them, very close to the micro, for reliable operation.

 

You can not leave a Vcc, AVcc, or Ground pin not connected, regardless of what other ports and pins you are suing on the micro.

 

What is known about the internal power bus structure is that the AVcc/Ground pins typically provide power to the analog portion of the chip, the ADC, DAC, Analog Comp, etc.

They also, typically, provide power for the PortA pins, ("A" for analog...), but there are some fine points in some of the data sheets regarding this.

 

Note also that the Xmega is a single core voltage chip.  You can't power part of the chip at 3.3 V and another part at 1.7V, everything has to be at the same voltage.

 

JC   

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You can't power part of the chip at 3.3 V and another part at 1.7V, everything has to be at the same voltage.

Of course an externally applied voltage reference for the ADC can differ, but it must not exceed your Avcc supply voltage (Vref< Avcc-0.6) 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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sukuwc wrote:
What I would like to know is if the power pins next to the ports actually belong to that port...
Possibly.   DocJC gave you an excellent answer, make sure to follow everything he listed.

 

The important fact, and this holds true for all MCUs/MPUs and other chips as well, is that power and ground need to be distributed evenly across the die.  Another reason is that the whisker (very small wire) that connects the chip lead to the die can only carry a limited amount of current, in most cases not enough to power the entire chip.

 

Just to give more detail, i found a post by Dan Laks at https://electronics.stackexchange.com/questions/128120/reason-of-multiple-gnd-and-vcc-on-an-ic

 

 

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Last Edited: Tue. Feb 27, 2018 - 05:29 PM
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Ok, thanks for the quick answers, I'm working on a layout and I plan to put every decoupling cap, avcc filtering and xtal circuitry right under the 100pin TQFP package of the 128A1U. So far seems to be a fairly straight forward layout.

 

Cheers, and thanks again for the great tips!

 

 

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DocJC wrote:
Only Microchip can answer that question for you.
Or your DMM. I would not be surprised if you measure an (almost) short or low resistance between all Vcc pins on a bare chip. (And also between all GND pins).

 

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com