Figure 6-4 describes the device power-down sequencing.
A. Time stamp
markers:
- T0 – MCU_PORz & PORz assert low
to put all processor resources in safe state. (0 ms)
- T1 – Main DDR, SRAM Core, and SRAM
CPU power supplies start ramp-down. (0.5 ms)
- T2 – Low voltage core supplies start
supply ramp-down. (2.5 ms)
- T3 - 1.8-V voltages start supply
ramp-down. (3.0 ms)
- T4 – 3.3V voltages start supply
ramp-down. (3.5 ms)
B. Any MCU or
Main dual voltage IO domains (VDDSHVn_MCU or VDDSHVn) being supplied by 3.3 V to support
3.3-V digital interfaces.
C. Any MCU or
Main dual voltage IO domains (VDDSHVn_MCU or VDDSHVn) being supplied by 1.8 V to support
1.8-V digital interfaces.
D. VDDSHV5
supports MMC1 signaling for SD memory cards. A dual voltage (3.3 V/1.8 V) power rail is
required for compliant, high-speed SD card operations. If SD card is not needed or
standard data rates with fixed 3.3-V operation is acceptable, then domain can be grouped
with digital IO 3.3-V power rail. If a SD card is capable of operating with fixed 1.8 V,
then domain can be grouped with digital IO 1.8-V power rail.
E. VDDA_3P3_USB is 3.3-V analog domain used for USB 2.0 differential interface signaling. A
low noise, analog supply is recommended to provide best signal integrity for USB data eye
mask compliance. If USB interface is not needed or data bit errors can be tolerated, then
domain can be grouped with 3.3-V digital IO power rail either directly or through a supply
filter.
F. VDDA_1P8_<clk/pll/ana> are 1.8V analog domains supporting clock oscillator, PLL and
analog circuitry needing a low noise supply for optimal performance. It is not recommended
to combine digital VDDSHVn_MCU and VDDSHVn IO domains since high frequency switching noise
could negatively impact jitter performance of clock, PLL and DLL signals. Combining analog
VDDA_1p8_<phy> domains should be avoided but if grouped, then in-line ferrite bead
supply filtering is required .
G. VDDA_1P8_<phy> are 1.8-V analog domains supporting multiple serial PHY interfaces.
A low noise, analog supply is recommended to provide best signal integrity, interface
performance and spec compliance. If any of these interfaces are not needed, data bit
errors or non-compliant operation can be tolerated, then domains can be grouped with
digital IO 1.8-V power rail either directly or through an in-line supply filter is
allowed.
H. VDDA_0P8_<dll/pll> are 0.8-V analog domains supporting PLL and DLL circuitry
needing a low noise supply for optimal performance. It is not recommended to combine these
domains with any other 0.8-V domains since high frequency switching noise could negatively
impact jitter performance of PLL and DLL signals.
I. MCU_PORz
and PORz must be asserted low for TΔ1 = 200 us MIN to ensure SoC resources enter into safe
state before any voltage begins to ramp down.
Figure 6-4 Combined MCU and
Main Domains, Primary Power-Down Sequence