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1.5.1.3
VCC current consumption in 3G connected mode
During a 3G connection, the module can transmit and receive continuously due to the Frequency Division Duplex
(FDD) mode of operation with the Wideband Code Division Multiple Access (WCDMA).
The current consumption depends on output RF power, which is always regulated by the network (the current
base station) sending power control commands to the module. These power control commands are logically
divided into a slot of 666 µs, 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 case scenario, corresponding to a continuous transmission and reception at maximum output power
(approximately 250 mW or 24 dBm), the average current drawn by the module at the VCC pins is considerable
(see the "Current consumption" section in LARA-R2 series Data Sheet [1]). At the lowest output RF power
(approximately 0.01 µW or –50 dBm), the current drawn by the internal power amplifier is strongly reduced. The
total current drawn by the module at the VCC pins is due to baseband processing and transceiver activity.
Figure 7 shows an example of the current consumption profile of the module in 3G WCDMA/HSPA continuous
transmission mode.
Current [mA]
700
600
500
400
300
200
100
0
1 slot
666 µs
Figure 7: VCC current consumption profile versus time during a 3G connection (TX and RX continuously enabled)
UBX-16010573 - R12
850 mA
Current consumption value
depends on TX power and
actual antenna load
170 mA
3G frame
10 ms
(1 frame = 15 slots)
LARA-R2 series - System Integration Manual
Time
[ms]
System description
Page 23 of 157
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