u-blox SARA-G3 Series User Manual

SARA-G3 series - System Integration Manual
UBX-13000995 - R06 Objective Specification System description
Page 38 of 218
1.6 System function interfaces
1.6.1 Module power-on
The power-on sequence of SARA-G3 series modules is initiated in one of these ways:
 Rising edge on the VCC pin to a valid voltage as module supply (i.e. applying module supply)
 Low level on the PWR_ON pin (normally high with external pull-up) for an appropriate time period
 RTC alarm (i.e. pre-programmed scheduled time by AT+CALA command)
1.6.1.1 Rising edge on VCC
When a SARA-G3 module is in the not-powered mode, it can be switched on by applying the VCC
supply.
The module is switched on when the voltage rises up to the VCC normal operating range minimum limit
(3.35 V) starting from a voltage value lower than 2.25 V, and with a proper voltage slope: the voltage
at the VCC pins must ramp from 2.5 V to 3.2 V within 4 ms to switch on the module. When the VCC
voltage is stabilized at its nominal value within the normal operating range, the module can be switched
on by a low level on PWR_ON pin (see section 1.6.1.2) or by RTC alarm (see section 1.6.1.3).
If the PWR_ON input pin is held low during the VCC apply phase, the SARA-G3 module switches on
when voltage rises up to the VCC normal operating range minimum limit (3.35 V).
1.6.1.2 Low level on PWR_ON
When a SARA-G3 module is in the power-off mode (i.e. switched off with valid VCC supply
maintained), the module can be switched on by forcing a low level on the PWR_ON input pin at least
for 5 ms.
The electrical characteristics of the PWR_ON input pin are different from the other digital I/O interfaces.
The input voltage thresholds are slightly different since the PWR_ON input pin is tolerant of voltages up to
the module supply level. The detailed electrical characteristics are described in SARA-G3 series Data
Sheet [1].
There is no internal pull-up resistor on the PWR_ON pin: the pin has high input impedance and is
weakly pulled to the high level 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 further design-in guidelines refer
to section 2.2.1).
1.6.1.3 RTC alarm
When a SARA-G3 module is in the power-off mode (i.e. switched off with valid VCC supply
maintained) and the RTC timing (32 kHz reference clock) is available, the module can be switched on
by an RTC alarm previously programmed by AT command at a scheduled time (refer to the u-blox AT
Commands Manual [2], AT+CALA command). The internal RTC block system will then initiate the module
boot sequence by instructing the Power Management Unit to turn on power. Also included in this setup is
an interrupt signal from the RTC block to indicate to the baseband processor that an RTC event has
occurred.
The RTC timing is automatically generated by the 32.768 kHz reference clock provided by the internal
oscillator on SARA-G350 modules. A valid external 32.768 kHz signal must be provided at the EXT32K

u-blox SARA-G3 Series Specifications

General

Brand	u-blox
Model	SARA-G3 Series
Category	GSM/GPRS Modules
Language	English