u-blox SARA-G3 Series System Integration Manual page 39

input pin of the SARA-G300 / SARA-G310 modules to enable RTC timing, otherwise the switch-on of
SARA-G300 / SARA-G310 modules by means of a pre-programmed RTC alarm is not possible (refer to
section 1.6.4).
1.6.1.4 Additional considerations
The module is switched on when the VCC voltage rises to the normal operating range (i.e. applying
module supply): the first time that the module is used, it is switched on in this way. SARA-G3 modules
can be switched off by means of the AT+CPWROFF command, entering power-off mode. In this state,
the digital input-output pads of the baseband chipset (i.e. all the digital pins of the module) are locked
in tri-state (i.e. floating). The power down tri-state function isolates the module pins from the
environment, when no proper operation of the outputs can be guaranteed.
The module can be switched on from power-off mode by forcing a proper start-up event (e.g. PWR_ON
low). After the detection of a start-up event, all the module digital pins are held in tri-state until all the
internal LDO voltage regulators are turned on in a defined power-on sequence. Then, as described in
Figure 13Figure 13, the baseband core is still held in reset state for a time interval: the internal reset
signal (which is not available on a module pin) is still low and all the digital pins of the module are
held in reset state. The reset state of all the digital pins is reported in the pin description table of
SARA-G3 Series Data Sheet
[1]. When the internal signal is released, the configuration of the module
interfaces starts: during this phase any digital pin is set in a proper sequence from the reset state to the
default operational configuration. Finally, the module is fully ready to operate when all interfaces are
configured.
Start-up PWR_ON
event can be set high
VCC
V_BCKP
P WR_ON
V_INT
Internal Reset
System State
BB P ads State Tristate / Floating
0 ms 5 ms
Figure 13: SARA-G3 series power-on sequence description
The Internal Reset signal is not available on a module pin, but the application can monitor the
V_INT pin to sense the start of the SARA-G3 series power-on sequence.
UBX-13000995 - R06
Start of interface
configuration
OFF
Internal Reset → Operational Operational
Internal Reset
8 ms ~35 ms
Objective Specification
SARA-G3 series - System Integration Manual
All interfaces
are configured
ON
~3 s
System description
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