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brownout on MCU's

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Simon:
can someone just explain what brownout is on an MCU (PIC) does it mean that the MCU will not operate if the voltage is too low as oposed to working in a random manner ?

RayJones:
Brownout refers to a supply that dips well below the proper value such that a device stops operating correctly and shortly returns back to normal.

Coined from when you see a dip in mains supplies, and the lights go "brown" for second or so.

With the mains situation, refrigerator motors may stall and burn out.
With micros, they may just latch up and refuse to run until given a proper reset.

You can get power watchdog chips that force and hold a reset for a period after such power drops, and many micros these days build this function in.

tecman:
Most microcontrollers today have a voltage monitoring circuit that will reset the MCU if the voltage reaches an internal threshold.  Some will sleep rather than reset if selected.

paul

desolatordan:

--- Quote from: RayJones on July 23, 2010, 10:21:15 pm ---Brownout refers to a supply that dips well below the proper value such that a device stops operating correctly and shortly returns back to normal.

--- End quote ---

It's important to note that during a brownout, digital circuits will often corrupt ram or eeprom. Brownout protection for microcontrollers will turn the MCU completely off during brownouts to ensure this doesn't happen.

Simon:
ao basically the brown out function will allow the MCU to work only with correct voltages ?

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