SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R08
Objective Specification
System description
Page 25 of 188
1.5.1.4
VCC current consumption in cyclic idle/active-mode (power saving enabled)
The power saving configuration is by default disabled, but it can be enabled using the appropriate AT command
(see
u-blox AT Commands Manual
[3], AT+UPSV command). When power saving is enabled, the module
automatically enters low power idle-mode whenever possible, reducing current consumption.
During idle-mode, the module processor runs with 32 kHz reference clock:
the internal oscillator automatically generates the 32 kHz clock on SARA-G340, SARA-G350, SARA-U2 series
a valid 32 kHz signal must be properly provided to the
EXT32K
input pin of the SARA-G300 and
SARA-G310 modules to let low power idle-mode, that otherwise cannot be reached by these modules.
When the power saving configuration is enabled and the module is registered or attached to a network, the
module automatically enters the low power idle-mode whenever possible, but it must periodically monitor the
paging channel of the current base station (paging block reception), in accordance to the 2G or 3G system
requirements, even if connected-mode is not enabled by the application. When the module monitors the paging
channel, it wakes up to the active-mode, to enable the reception of paging block. In between, the module
switches to low power idle-mode. This is known as discontinuous reception (DRX).
The module processor core is activated during the paging block reception, and automatically switches its
reference clock frequency from 32 kHz to the 26 MHz used in active-mode.
The time period between two paging block receptions is defined by the network. This is the paging period
parameter, fixed by the base station through broadcast channel sent to all users on the same serving cell.
In case of 2G radio access technology, the paging period varies from 470.8 ms (DRX = 2, length of 2 x 51
2G frames = 2 x 51 x 4.615 ms) up to 2118.4 ms (DRX = 9, length of 9 x 51 2G frames = 9 x 51 x 4.615 ms)
In case of 3G radio access technology, the paging period can vary from 640 ms (DRX = 6, i.e. length of 26
3G frames = 64 x 10 ms) up to 5120 ms (DRX = 9, length of 29 3G frames = 512 x 10 ms).
Figure 11 roughly describes the current consumption profile of SARA-G340, SARA-G350 and SARA-U2 series, or
specifically of SARA-G300 and SARA-G310 modules when their
EXT32K
input pin is fed by an external 32 kHz
signal with characteristics compliant to the one specified in
SARA-G3 series
Data Sheet
[1], when power saving is
enabled. The module is registered with the network, automatically enters the very low power idle-mode, and
periodically wakes up to active-mode to monitor the paging channel for paging block reception.
20-30 ms
IDLE MODE
ACTIVE MODE
IDLE MODE
300-600 µA
Active Mode
Enabled
Idle Mode
Enabled
300-600 µA
60-120 mA
2G case: 0.44-2.09 s
3G case: 0.61-5.09 s
IDLE MODE
20-30 ms
ACTIVE MODE
Time [s]
Current [mA]
100
50
0
Time [ms]
Current [mA]
100
50
0
4-5 mA
60-120 mA
RX
Enabled
20-40 mA
DSP
Enabled
Figure 11: VCC current consumption profile versus time of SARA-G340, SARA-G350, SARA-U2 series or SARA-G300, SARA-G310
(with the EXT32K input fed by a proper external 32 kHz signal), when registered with the network, with power saving enabled:
the very low power idle-mode is reached and periodical wake up to active-mode are performed to monitor the paging channel
