8.3.2.3 Backup Mode Entry (Shutdown)
The figure below shows the recommended power-down sequence to place the SAMA5D2 LPDDR2 SIP either in Backup mode or in Backup mode with the LPDDR2 in self-refresh. The SHDN signal, an output of the Shutdown Controller (SHDWC), signals the shutdown request to the power supply. This output is supplied by VDDBU that is present in Backup mode. Placing the LPDDR2 memory in self-refresh while in Backup mode requires maintaining VDDIODDR, DDRM_VDD18 and DDRM_VDD12 as well. One possible way to signal this additional need to the power supply is to position one of the general-purpose I/Os supplied by VDDBU (PIOBUx) in a predefined state.
| Symbol | Parameter | Conditions | Min | Max | Unit |
|---|---|---|---|---|---|
| tRSTPD | Reset delay at power-down | From NRST low to the first supply turn-off | 0 | – | ms |
| t1 | DDRM_VDD12 to DDRM_VDD18 delay | From DDRM_VDD12 zeroed to DDRM_VDD18 turn-off | 0 | – | |
| t2 | LPDDR2 power-off delay | From NRST low to DDRM_VDD18 zeroed | – | 2000 |