When the power supply on a microcontroller falls under a certain threshold, a brown-out conditions occurs and RAM memory may get corrupted. Provided that every power down sequence of the circuit can mean a potential brown-out condition, I always enable the Brown-out Detection Reset mechanism when working with microcontrollers.
I was wondering if there are any situations in which it is not recommended to enable the Brown-out Reset feature?
Best Answer
As noted, enabling the brown-out circuit will often increase current consumption. Further, because manufacturers generally want to ensure that the brown-out circuit will trip on any voltage that might be low enough to cause other parts of the chip to function, many parts will be able to operate at a lower voltage with brown-out disabled. For example, a controller might work most of the time down to 1.5 volts at room temperature but, under certain stressful conditions (such as elevated temperature) could malfunction at 1.99 volts. To ensure that the device would reset under any condition where a malfunction might occur, the brown out circuit might be designed to trip at 2.1 volts +/- 100mV.
If a device with such a controller were powered from two alkaline AA batteries, enabling the brownout circuit may cause the device to become unusable with a battery voltage of 1.1 volts per cell, and would likely cause it to cease operation by the time the voltage reached 1.05 volts per cell. Disabling the brownout circuit would likely extend operation down to at least 0.9 volts per cell, and possibly even 0.75 volts per cell. If no plausible malfunction that could occur at low voltage could cause any harm beyond increased drain on junk batteries, disabling the brownout circuit would be a simple way of improving battery life, even if it didn't reduce the current draw from usable batteries.