SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R26
System description
Page 29 of 217
1.5.1.4
VCC current consumption in cyclic idle/active mode (power saving enabled)
The power saving configuration is disabled by default, but it can be enabled using the appropriate AT command
(see the
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 paging block reception. 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.
For 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)
For 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 14 roughly describes the current consumption profile 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
the
SARA-G3 series
Data Sheet
[1]), or the SARA-G340 and SARA-G350 modules, or the SARA-U2 modules,
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
Active Mode
Enabled
Idle Mode
Enabled
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
RX
Enabled
DSP
Enabled
Figure 14: VCC current consumption profile versus time of the SARA-G300 and SARA-G310 modules (with the EXT32K input fed
by a proper external 32 kHz signal), or the SARA-G340 and SARA-G350 modules, or the SARA-U2 modules, 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
