TOBY-L4 series - System Integration Manual
UBX-16024839 - R04
System description
Page 26 of 143
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.
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/DC-HSPA+
continuous transmission mode.
It must be noted that the actual current consumption of the module in 3G connected mode depends also on the
specific concurrent activities performed by the integrated CPU, beside the actual Tx power and antenna load.
Time
[ms]
3G frame
10 ms
(1 frame = 15 slots)
Current [mA]
Current consumption value
depends on TX power and
actual antenna load
170 mA
1 slot
666 µs
850 mA
0
300
200
100
500
400
600
700
Figure 7: VCC current consumption profile versus time during a 3G connection (TX and RX continuously enabled)