The S3PORTC90FS is a low-power reset circuit that provides the following feature:
Power-On Reset (POR) signal that monitors the absolute value of two supplies. The logic level of this reset signal is set by the level of the power supplies and can be delayed by an internal RC oscillator and counter.
The internal RC oscillator can also be used to drive other circuitry if required
During sleep mode which requires low power RC oscillator generates a very low clock frequency
The S3PORTC90FS uses a threshold detect circuit to establish the point when it is safe for circuitry to begin functioning. This detection circuit guarantees that the supply is at a sufficient level for the circuitry to operate correctly.
The POR output signal can be delayed by varying amounts, should it be required by changing the counter division.