While reading a datasheet of FS84;FS85, i found the deep-fs mode in the simplified functional state graph. But the data sheet only mentions about how to get in the Deep-FS mode, not the meaning of it. What does Deep-FS mode means in detail, and what's the difference with Normal-FS mode? Why does we need Deep-FS mode?
Deep failsafe is when, from normal mode Normal-FS, the device has a critical failure (for example several consecutive bad watchdog, RESETB asserted for longer than 8s, VPRE OV, REG Thermal shutdown, …), and the device needs to go into deep failsafe deep-FS mode, in order to shutdown everything for safety purposes, and try again to power up later on.
Normal-FS is when device operates normally and all is good, deep-FS is when everything is shutdown because of critical failure.