atmega & reversed polarity


I "finally" managed to power in reversed polarity a DIY circuit including an atmega328 + some components (opamp, thermopile, ds18b20). The battery pack was nearly depleted so i probably applied -3.5V to Vcc pin for 1sec. According with the specs the absolute max rating is -0.5V. For now there are no "obvious" faults with the circuit. Was i simply lucky or should i expect further, subtle problems?


Damaged components do not always fail immediately. Moving forward whether a component is damaged or not, you are going suspect it every time there is an issue.

What kind of battery pack - ie how much current could it easily have produced?

In reversing the supply all the input protection diodes are going to conduct, and if you are lucky they will have taken the current without burning out. If unlucky they all overheated and won’t work as well (possibly damaging nearby transistors and interconnect).

One piece of advice: always use colour coded wires for supply (red for +5V and black for 0V for instance). Colour code everything and you won’t make that mistake easily!