8.4.3 Backup Mode Exit (Wake-up)

The figure below shows the recommended power-up sequence to wake up the device from Backup mode. Upon a wake-up event, the Shutdown Controller toggles its SHDN output back to VDDBU to request the power supply to restart. Except for VDDIODDR which may already be present if the external DDR memory was placed in Self-refresh mode, this power-up sequence is the same one as presented in the figure “Recommended Power-up Sequence”. In particular, the definitions of Group 1 and Group 2 are the same.

Figure 8-4. Recommended Power Supply Sequencing at Wake-up
Table 8-5. Power-up Timing Specification
Symbol Parameter Conditions Min Max Unit
t1 Group 2 to Group 1 delay Delay from the last Group 2 established(1) supply to the first Group1 supply turn-on 1 – ms
t2 Group 1 delay(2) Delay from the first group 1 established supply to the last Group 1 established supply – 1
tRSTPU Reset delay at power-up From the last established supply to NRST high. 1 –
Note:
  1. An “established” supply refers to a power supply established at 90% of its final value.
  2. Also applies to VDDIODDR when considered as part of Group 1.