58.4.1 Power-Up and Power-Down

At power-up, from a power supply sequencing perspective, the SAM9X60 power supply inputs are categorized into three independent groups:
  • VDDCORE
  • VDDIN33
  • Periphery group containing all other power supply inputs except VDDBU

The figure below shows the recommended power-up sequence. Note the following:

  • VDDBU
    • When supplied from a precharged storage element (battery or supercapacitor), VDDBU is an always-on supply input and is therefore not part of the power supply sequencing.
    • When no storage element is used on VDDBU in the application, VDDBU must be tied to VDDIN33.
    • When a supercapacitor is used in the application to power VDDBU during Backup mode, this element must be isolated from VDDBU during its (slow) charge, so that VDDBU closely follows VDDIN33. In table Power-up Timing Requirements, the parameter t0 limits the delay to establish VDDBU after VDDIN33.
  • VDDOUT25 is the output of the internal 2.5V VDDOUT25 regulator, therefore, there is no power supply requirement on this pin. VDDOUT25 is automatically started at VDDIN33 rise when VDDIN33 is above its Power-On-Reset threshold.
Figure 58-2. Recommended Power Sequence at Power-up
Table 58-8. Power-up Timing Requirements
Symbol Parameter Conditions(1) Min Max Unit
t0 VDDBU Delay Delay from established VDDIN33 to established VDDBU – 0.2 ms
t1 VDDIN33 to Periphery Group delay Delay from established VDDIN33 to the first established Periphery Group supply 0 – ms
t2 Periphery Group to VDDCORE delay Delay from the last established Periphery Group supply to VDDCORE supply turn-on 0 – ms
t3 Reset Delay at power-up From established VDDCORE to NRST high 8 – ms
Note:
  1. The term "established" refers to a power supply established to 90% of its final value.

The following figure shows the SAM9X60 power-down sequence that starts by asserting the NRST line to 0. Once NRST is asserted, the supply inputs can be immediately shut down without any specific timing or order. VDDBU may not be shut down if the application uses a backup storage element on this supply input.

Figure 58-3. Recommended Power Sequence at Power-down
Table 58-9. Power-down Timing Requirements
Symbol Parameter Conditions Min Max Unit
tRSTPD NRST delay at power-down Delay from NRST low to the first supply out of its operating range 0 – ms