8.2.1 System Power-Up

At power-up, from a power supply sequencing perspective, the SAM9X60D1G-I/LZB power supplies are categorized into five independent groups:
  • 5V_MAIN (main supply)
  • VDDBU (backup group)
  • VDD_3V3 (periphery group) containing VDDUTMII, VDDANA, VDDOSC, VDDNF, VDDIOPx and VDDQSPI inputs
  • VDDIOM (memory group)
  • VDDCORE (core group)

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

  • VDDBU
    • When supplied from a precharged storage element (battery, supercapacitor or micro-battery), 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 VDD_3V3.
    • When a supercapacitor or a micro-battery is used in the application to power VDDBU in Backup mode, this element must be isolated from VDDBU during its (slow) charge, so that VDDBU closely follows VDD_3V3. In table Power-Up Timing Specification, the parameter t1 limits the delay to establish VDDBU after VDD_3V3.
  • VDDOUT25 is the output of the internal 2.5V regulator, and therefore there is no power supply requirement on this pin. VDDOUT25 is automatically started at VDD_3V3 rise when VDD_3V3 is above its Power-On-Reset threshold.
Figure 8-2. Recommended Power-Up Sequence
Note:
  1. If VDDQSPI is supplied externally, the power must be applied at the same time or after the presence of VDD_3V3 and before the presence of VDDIOM.
Table 8-2. Power-Up Timing Requirements
SymbolParameterConditions(1)MinTypMaxUnit
t0nSTRT deglitch timenSTRT pin falling edge0.5ms
t1VDDBU delayDelay from established VDD_3V3 to established VDDBU0.2ms
t2VDD_3V3 to Periphery group delayDelay from established VDD_3V3 to the periphery group established supply8ms
t3Periphery group to VDDCORE delayDelay from the periphery group established supply to the VDDCORE supply turn-on4ms
t4Reset delay at power-upFrom established VDDCORE to NRST high16ms
Note:
  1. The term "established" refers to a power supply established to 90% of its final value.