8.3.2.1 Power-up Considerations
At power-up, from a supply sequencing perspective, the SAMA5D2 LPDDR2 SIP power supply inputs are categorized into two groups:
- Group 1 (core group) contains VDDCORE, VDDUTMIC, VDDHSIC and VDDPLLA.
- Group 2 (periphery group) contains all other power supply inputs
except VDDFUSE.The figure below shows the recommended power-up sequence. Note that:
- VDDBU, when supplied from a battery, is an always-on supply input and is therefore not part of the power supply sequencing. When no backup battery is present in the application, VDDBU is part of Group 2.
- VDDFUSE is the only power supply that may be left unpowered during operation. This is possible if and only if the application does not access the Customer Fuse Matrix in Write mode. It is good practice to turn on VDDFUSE only when the Customer Fuse Matrix is accessed in Write mode, and to turn off VDDFUSE otherwise.
| 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 Group 1 supply turn-on | 0 | – | ms |
| t2 | Group 1 delay | Delay from the first Group 1 established supply to the last Group 1 established supply | – | 1 | |
| t3 | VDDFUSE to VDDBU delay | Delay from VDDBU established to VDDFUSE turn-on | 1 | – | |
| t4 | DDRM_VDD18 to DDRM_VDD12 delay | Delay from the DDRM_VDD18 established to DDRM_VDD12 turn-on | 0 | – | |
| t5 | LPDDR2 power-on delay | Delay from DDRM_VDD18 turn-on to DDRM_VDD12 established | – | 20 | |
| tRSTPU | Reset delay at power-up | From the last established supply to NRST high | 1 | – |
Note:
- An “established” supply refers to a power supply established at 90% of its final value.