Figure 6-6
describes the device power-down sequencing.
- Time Stamp Markers
T0 – MCU_PORz & PORz assert low to put
all processor resources in safe state.
(0ms)
T1 – Main DDR, SRAM Core & SRAM CPU
power supplies start ramp-down. (0.5ms)
T2 –
Low voltage core supplies start supply ramp-down.
(2.5ms)
T3 - 1.8V voltages start supply
ramp-down. (3.0ms)
T4 – 3.3V voltages start
supply ramp-down. (3.5ms)
- Any MCU or Main
dual voltage IO supplies (VDDSHVn_MCU or VDDSHVn) being
supplied by 3.3V to support 3.3V digital interfaces
- Any MCU or Main
dual voltage IO supplies (VDDSHVn_MCU or VDDSHVn) being
supplied by 1.8V to support 1.8V digital interfaces. When
eMMC memories are used, Main 1.8V supplies could have a
ramp-down aligned to T1 due to PDN designs grouping supplies
with VDD_MMC0.
- VDDSHV5 supports
MMC1 signaling for SD memory cards. A dual voltage
(3.3V/1.8V) power rail is required for compliant, high-speed
SD card operations. If compliant highspeed SD card operation
is needed, then an independent, dual voltage (3.3V/1.8V)
power source and rail are required. The start of ramp-down
from 3.3V/1.8V will be same as other 3.3V domains as shown.
If SD card is not needed or standard data rates with fixed
3.3V operation is acceptable, then domain can be grouped
with digital IO 3.3V power rail. If a SD card is capable of
operating with fixed 1.8V, then domain can be grouped with
digital IO 1.8V power rail.
- VDDA_3P3_USB is
3.3V 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. The start of ramp-down from 3.3V will be same as
other 3.3V domains as shown. If USB interface is not needed
or data bit errors can be tolerated, then domain can be
grouped with 3.3V digital IO power rail either directly or
through a supply filter.
- VDDA_1P8_<phy> are 1.8V 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 1.8V power rail either directly or through an in-line
supply filter is allowed.
- VDD_MMC0 is 1.8V
digital supply supporting MMC0 signaling for eMMC interface
and must ramp-down at time stamp T1 before VDD_CORE starts
ramp-down. Any MCU or Main dual voltage IO operating at 1.8V
can be grouped with VDD_MMC0 into a common power rail with
power down time stamp T1. If MMC0 or eMMC0 interface is not
needed, then domain can be grouped with digital IO 1.8V
power rail and ramp-down at time stamp T3.
- VDD_MCU is a
digital voltage supply with a wide operational voltage range
and power sequencing flexibility, enabling it to be grouped
and ramped-down with either 0.8V VDD_CORE at time stamp T2
or 0.85V RAM array domains (VDDAR_xxx) at time stamp
T1.
- 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 analog VDDA_1P8_<phy>
domains or digital VDDSHVn_MCU and VDDSHVn IO domains since
high frequency switching noise could negatively impact
jitter performance of clock, PLL and DLL signals.
- MCU_PORz and PORz
must be asserted low for TΔ1 = 200us min to ensure SoC
resources enter into safe state before any voltage begins to
ramp down.