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I am using an ATxmega128D4 (Atmel XMEGA D4 Datasheet) (not Atmega128D) for my project. Among the 4 Vccs(1 is AVcc and 3 Vcc) of the microcontroller, I have to power 1 of the Vccs from a 1S Lipo battery which gives a voltage 4.2V, capacity 500mAh. From the datasheet of Atmega128D I found that absolute max voltage rating is 4V (max 3.6V for normal operation). My question is if connect this 4.2V lipo to power one of these Vccs of the microcontroller, will it destroy my microcontroller? FYI I am not exceeding the current rating of the microcontroller though.

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    \$\begingroup\$ It's not clear why you are asking this. You have read the manufacturer's datasheet, found 4 V as the absolute maximum supply voltage and want us to tell you that 4.2 V will be OK? Why? \$\endgroup\$ – Transistor Jul 11 at 22:59
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    \$\begingroup\$ Beyond the absolute max voltage rating, anything can happen. I would just drop the voltage with a diode at least if for some reason you don't want to use a linear regulator. Technically you shouldn't be running beyond 3.6V anyways. Just because a component won't be damaged does not mean it will operate properly. \$\endgroup\$ – DKNguyen Jul 11 at 22:59
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    \$\begingroup\$ One of the VCCs? No, they all must be powered from the same supply. \$\endgroup\$ – Justme Jul 11 at 23:15
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    \$\begingroup\$ Please provide a link to the data sheet - Microchip doesn't show an Atmega128D. The usual Atmega128 devices have a 5.5 volt limit. \$\endgroup\$ – Kevin White Jul 12 at 0:53
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    \$\begingroup\$ @KevinWhite here is the link of the datasheet: ww1.microchip.com/downloads/en/devicedoc/… \$\endgroup\$ – Shu Jul 12 at 5:23
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Yes, overvoltage will break a microcontroller. But if you are powering one supply pin with other voltage than others, that is not a defined operating condition either.

The XMega device datasheet you linked to (which is different from Mega device) has a defined operating range of up to 3.6V. It does not get permanent damage if you exceed that, but it is not guaranteed to work either. The absolute maximum rating is 4.0V, and permanent damage can happen when this is exceeded.

Note that both VCC and AVCC must be within the 3.6V limit, and in addition AVCC and VCC must be within 0.3V of each other. There is no explict mention of it in the datasheet, but all VCC pins must be connected and to the same supply voltage, and they are not allowed to be powered from separate sources. The maximum difference between VCC pins is not specified. Some MCUs define this allowable difference. Also all power supply and ground pins, including analog supplies and grounds, must be connected, they cannot be left unconnected.

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Chapter 32 of the data sheet says the absolute maximum voltage allowed is 4V, so they won't promise that it will survive 4.2V

Stresses beyond those listed in Table 32-1 under may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

enter image description here you might get lucky.

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  • \$\begingroup\$ Thanks a lot, everyone. I have got my answer. I had a typo of the MCU model I mentioned, I am so sorry about that. \$\endgroup\$ – Shu Jul 13 at 0:53

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