Q&A: How to use the AM18x5 to control the low-power state of an MCU?

Full question(s):

How can I use the AM18x5 RTC to control the low-power state of an MCU?

Answer(s):

The AM18X5 enables a variety of system implementations in which the AM18X5 can
control power usage by other elements in the system.  We recommand using a Vss Power Switched, in which the internal power switch of the AM18X5 is used to completely turn off the MCU and/or other system elements.

In this case the PSW/nIRQ2 output is configured to generate the SLEEP function. Under normal circumstances, the PSW/nIRQ2 pin is pulled to VSS with approximately 1 Ω of resistance, so that the MCU receives full power.  When the AM18X5 enters the SLEEP state the PSW/nIRQ2 pin is opened and power is
completely removed from the MCU.

How to make Am18x5 exit sleep state?

• By AM18x5 internal countdown timer setting
  

Through this way, the application can control the power consumption periodically.

• By AM18x5 Ext1 Input Interrupt

Through this way, the application can exit sleep state and resume the power supply when a valid Ext1 interrupt is detected, such as when a button input occurs, etc.