what is power on reset?

 Power-on reset (POR) is a circuit that ensures a reliable startup and initialization of an electronic device when power is initially applied or restored after a power interruption. It is commonly found in microcontrollers, microprocessors, and other digital systems.

The primary function of a power-on reset circuit is to generate a reset signal that resets the device's internal state and initializes it to a known condition upon power-up. This is necessary because when power is first applied, the voltage levels may be unstable or unknown, which can lead to unpredictable behavior or incorrect operation of the device.

The power-on reset circuit typically monitors the power supply voltage and generates a reset signal when the voltage rises above a certain threshold level. This ensures that the device remains in a reset state until the power supply stabilizes and reaches a suitable level for proper operation.

Example of a POR details mentioned on the datasheet as following information ,

The reset signal generated by the power-on reset circuit is typically applied to the device's reset input, causing it to start execution from a predefined address in memory. This allows the device to go through its initialization routine, configure its internal registers, and prepare for normal operation.

Example POR Details of a Sensor

(MLX90615)

In addition to power-on reset, many systems also incorporate other reset mechanisms such as brownout detection and external reset buttons to handle various situations where the device may need to be reset to a known state during operation.

Overall, power-on reset circuits provide a reliable and controlled startup sequence for electronic devices, ensuring that they initialize properly and operate as intended when power is applied. To prevent any unexpected behavior, the POR circuit detects when the power supply voltage reaches a stable level and generates a reset signal that resets the device to a known state. The POR circuit is usually implemented using a combination of analog and digital components, including capacitors, resistors, comparators, and logic gates. It is commonly used in microcontrollers, digital signal processors, and other digital systems to ensure reliable and consistent operation after power-up.