SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R26 System description
Page 28 of 217
1.5.1.3 VCC current consumption in 3G connected mode
During a 3G connection, the SARA-U2 modules can transmit and receive continuously due to the Frequency
Division Duplex (FDD) mode of operation with Wideband Code Division Multiple Access (WCDMA).
The current consumption depends again on output RF power, which is always regulated by network commands.
These power control commands are logically divided into a slot of 666 µs, and so the rate of power change can
reach a maximum rate of 1.5 kHz.
There are no high current peaks as in the 2G connection, since transmission and reception are continuously
enabled due to FDD WCDMA implemented in the 3G that differs from the TDMA implemented in the 2G case.
In the worst scenario, corresponding to a continuous transmission and reception at maximum RF output power
(approximately 250 mW or 24 dBm), the average current drawn by the module at the VCC pins is high (see the
SARA-U2 series Data Sheet [2]). Even at lowest RF output power level (approximately 0.01 µW or -50 dBm), the
average current is still not so low as in the equivalent 2G case, also due to module continuous baseband
processing and transceiver activity.
Figure 13 shows an example of the current consumption profile of SARA-U2 series modules in 3G
WCDMA/HSPA continuous transmission and reception mode. For detailed current consumption values during a
3G connection, see the SARA-U2 series Data Sheet [2].
Time
[ms]
3G frame
10 ms
(1 frame = 15 slots)
Current [mA]
Current consumption
depends on TX power and
actual antenna load
170 mA
1 slot
666 µs
850 mA
0
300
200
100
500
400
600
700
800
Figure 13: VCC current consumption profile versus time during a 3G connection (TX and RX continuously enabled)
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