AN3271

Basic functionality

Doc ID 17933 Rev 2

5/29

1

Basic functionality

1.1

Safe power-up

If the system is off, press the PB button to safely power up. EN output is asserted and power

for the application is enabled. Proper power-up has to be confirmed from a processor by

1.2

Interrupt assertion

If the device is on, press the PB button to assert an interrupt to the processor. The

processor can then perform backup routines and prepare the application for shutdown,

reset, display the menu, etc.

1.3

Power-down after long push (optional)

If the application is not responding to the interrupt (e.g. program freezes), press the PB

button and SR button simultaneously to power down the application regardless of processor

response. The time needed for both buttons to be held is adjustable by external capacitor

Figure 2.

Simplified timing sequence for option “enable deasserted after long push”

1.