Embedian, Inc.
147
SMARC-iMX8MM Computer on Module User’s Manual
v. 1.2
4.1.2.
No
Separate
Standby
Voltage
There
is
no
separate
voltage
rail
for
standby
power,
other
than
the
very
low
current
RTC
voltage
rail.
SMARC
‐
iMX8MM
operating
and
standby
power
comes
from
the
single
set
of
VDD_IN
pins.
This
suits
battery
power
sources
well,
and
is
also
easy
to
use
with
non
‐
battery
sources.
4.1.3.
RTC/Backup
Voltage
RTC
backup
power
is
brought
in
on
the
VDD_RTC
rail.
The
RTC
consumption
is
typically
15
microA
or
less.
The
allowable
VDD_RTC
voltage
range
shall
be
2.0V
to
3.25V.
The
VDD_RTC
rail
is
sourced
from
a
Carrier
based
Lithium
cell,
or
it
may
be
left
open
if
the
RTC
backup
functions
are
not
required.
SMARC
‐
iMX8MM
module
is
able
to
boot
without
a
VDD_RTC
voltage
source.
Lithium
cells,
if
used
on
Carrier,
shall
be
protected
against
charging
by
a
Carrier
Schottky
diode.
The
diode
is
placed
in
series
with
the
positive
battery
terminal.
The
diode
anode
is
on
the
battery
side,
and
the
cathode
on
the
Module
VDD_RTC
side.
Note
that
if
a
Super
cap
is
used,
current
may
flow
out
of
the
Module
VDD_RTC
rail
to
charge
the
Super
Cap.
4.1.4.
Power
Sequencing
The
Module
signal
CARRIER_PWR_ON
exists
to
ensure
that
the
Module
is
powered
before
the
main
body
of
Carrier
circuits
(those
outside
the
power
and
power
control
path
on
the
Carrier).
The
main
body
of
Carrier
board
circuits
should
not
be
powered
until
the
Module
asserts
the
CARRIER_PWR_ON
signal
as
a
high.
Module
hardware
will
assert
CARRIER_PWR_ON
when
all
Module
supplies
necessary
for
Module
booting
are
up.
The
IO
power
of
carrier
board
will
be
turn
on
at
the
stage
of
power
on
sequence.
If
the
IO
power
of
carrier
board
been
turn
on
earlier
than
the
SMARC
module,
the
power
on
carrier
board
might
feedback
to
SMARC
