48.4.1 Power-Up and Power-Down

At power-up, from a power supply sequencing perspective, the power supply inputs are categorized into independent groups. The figure below shows the recommended power-up sequence by group.

Note that:

VBAT
- When supplied from a pre-charged storage element (battery or super-capacitor), VBAT is an always-on supply input and is therefore not part of the power supply sequencing.
- When no storage element is used on VBAT in the application, VBAT must be tied to VDD3V3.

Figure 48-2. Recommended Power-Up Sequence with VDDCORE/VDDPLL Externally Supplied

Table 48-7. **Recommended Power Sequence at Power-Up**
Symbol	Parameter	Conditions	Min	Max	Unit
t₀	VDDCORE delay	Delay from VDD3V3 established to VDDLCD turn-on	0	–	ms
t₁	Periphery supply timing	Delay from the last established periphery supply (VDDLCD) to VDDCORE turn-on	0	1	ms
t_RES	Reset time	See VDDCORE Power-On-Reset	–

Figure 48-3. Recommended Power-Down Sequence with VDDCORE/VDDPLL Externally Supplied

Table 48-8. Power-Down Timing Specifications
Symbol	Parameter	Conditions	Min	Max	Unit
t₀	VDDCORE delay	Delay from VDDCORE out of its operating range to the first of (VDDLCD, VDD3V3) out-of-range	0	–	ms
t₁	Periphery supply timing	Delay from the periphery supply out-of-range to the last one	–	10	ms