SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R08
Objective Specification
System description
Page 31 of 188
1.6
System function interfaces
1.6.1
Module power-on
1.6.1.1
Switch-on events
Table 9 summarizes the possible switch-on events for the SARA-G3 and SARA-U2 series modules.
SARA-G3
SARA-U2
From
Not-Powered Mode
Applying valid
VCC
supply voltage (i.e.
VCC
rise edge),
ramping from 2.5 V to 3.2 V within 4 ms
Applying valid
VCC
supply voltage (i.e.
VCC
rise edge),
ramping from 2.5 V to 3.2 V within 1 ms
From
Power-Off Mode
Low level on
PWR_ON
pin for 5 ms min.
Low pulse on
PWR_ON
pin for 50 µs min. / 80 µs max.
RTC alarm programmed by AT+CALA command
(Not supported by SARA-G300 / SARA-G310)
RTC alarm programmed by AT+CALA command
RESET_N
pin released from low level
Table 9: Summary of SARA-G3 and SARA-U2 modules’ switch-on events
When the SARA-G3 and SARA-U2 series modules are in the not-powered mode (i.e. switched off with the
VCC
module supply not applied), they can be switched on by:
Rising edge on the
VCC
supply input to a valid voltage for modules supply: the modules switch on applying
VCC
supply starting from a voltage value lower than 2.25 V, providing a fast
VCC
voltage slope, as it must
ramp from 2.5 V to 3.2 V within 4 ms on SARA-G3 modules and within 1 ms on SARA-U2 modules, and
reaching a proper nominal
VCC
voltage value within the normal operating range.
Alternately, the
RESET_N
pin can be held low during the
VCC
rising edge, so that the module switches on
by releasing the
RESET_N
pin when the
VCC
voltage stabilizes at its nominal value within the normal range.
The status of the
PWR_ON
input pin of SARA-G3 and SARA-U2 series modules while applying the
VCC
module
supply is not relevant: during this phase the
PWR_ON
pin can be set high or low by the external circuit.
When the SARA-G3 and SARA-U2 series modules are in the power-off mode (i.e. switched off by means of the
AT+CPWROFF command, with valid
VCC
module supply applied), they can be switched on by:
Low level / pulse on
PWR_ON
pin, which is normally set high by an external pull-up, for a valid time period.
As described in Figure 17, there is no internal pull-up resistor on the
PWR_ON
pin of the modules: the pin has
high input impedance and is weakly pulled high by the internal circuit. Therefore the external circuit must be
able to hold the high logic level stable, e.g. providing an external pull-up resistor (for design-in see section 2.3.1).
The
PWR_ON
input voltage thresholds are different from the other generic digital interfaces of the modules:
refer to
SARA-G3 series Data Sheet
[1] and
SARA-U2 series Data Sheet
[2] for detailed electrical characteristics.
Baseband
Processor
15
PWR_ON
SARA-G3 / SARA-U2 series
Power-on
Power
Management
Power-on
Figure 17: PWR_ON input description
The SARA-G340, SARA-G350 and SARA-U2 series can be also switched on from power-off mode by:
RTC alarm pre-programmed by AT+CALA command at specific time (see
The SARA-U2 series modules can be also switched on from power-off mode by:
Low pulse on the
RESET_N
pin, which is normally set high by an internal pull-up (refer to section 1.6.3 and
to the
SARA-U2 series Data Sheet
[2] for the description of the
RESET_N
input electrical characteristics).
