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Apalis Carrier Board Design Guide
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3.4 Power Sequences
The Apalis module starts booting as soon as the main voltage rail is applied to the module. If an
Apalis system should boot directly when the main power is applied to it, the carrier board needs to
ramp up the 3.3V main voltage for the module as soon as power is applied (e.g. 7-27 V). The
Apalis module will ramp up the internal power rails. When this rails are stable, the
POWER_ENABLE_MOCI goes high in order to signal the carrier board that the peripheral supplies
need to ramp up. The peripheral power rails on the carrier board need to ramp up in a correct
sequence. The sequence starts normally with the highest voltage (e.g. 5V) followed by the lower
voltages (e.g. 3.3V then 1.5V and so on). Peripherals normally require that a lower voltage rails is
never present if a higher rail is missing. Check the datasheet of all peripheral components on the
carrier board for a proper sequencing.
Especially PCIe devices require stable power supplies for at least 100ms before releasing the reset.
The Apalis modules guarantees to apply the reset output RESET_MOCI# not earlier than 120ms
after the POWER_ENABLE_MOCI goes high. This gives the carrier board a maximum time of 20ms
for ramping up all power rails. Some Apalis module might have longer delay, but in order to be
compatible with all Apalis modules, count on the previous stated numbers.
Figure 57: Power-up sequence
Depending on the operating system, a shutdown sequence can be initiated. Some system may
benefit from shutting down instead of just removing the main power supply since it is possible to
bring the mass storage devices to a controlled state. Check whether a shutdown is preferable for a
certain operating system. Some operating system may not provide the shutdown function.
Since it is not allowed that a lower voltage rail is present when the higher one is already shut
down, the sequence of shutting down the peripheral voltages needs to be considered. The lower
voltages (e.g. peripheral 3.3V) need to ramp down before the higher ones do (e.g. peripheral 5V).
7-27V Carrier Board in
VCC input for Module
Module internal Rails
POWER_ENABLE_MOCI
5V for Perpherals on CB
3.3V for Perpherals on CB
RESET_MOCI#
WAKE1_MICO#
N
o
rm
a
l
P
o
w
e
r
u
p
(
O
F
F
-
>
R
U
N
)
State
UPG
UPG -> RUN
RUN
>120ms
<20ms
Module internal Reset
RESET_MICO#
>0ms