User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information System description
Page 25 of 116
Figure 11 reports the current consumption profiles in GPRS mode with 4 slots used to transmit.
Time [ms]
RX
slot
unused
slot
TX
slot
TX
slot
TX
slot
TX
slot
MON
slot
unused
slot
RX
slot
unused
slot
TX
slot
TX
slot
TX
slot
TX
slot
MON
slot
unused
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
Current [A]
200mA
~170mA
Peak current
depends on
TX power
~170mA
GSM frame
4.615 ms
(1 frame = 8 slots)
1.5
1.0
0.5
0.0
2.5
2.0
~40mA
1400 mA
Figure 11: VCC current consumption profile versus time during a GPRS/EDGE connection (4TX slots, 1 RX slot), with VCC=3.8 V
In case of EDGE connections the VCC current consumption profile is very similar to the GPRS current profile, so
the image shown in Figure 11 is valid for EDGE as well.
1.5.3.2 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 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, thus 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
output power (approximately 250 mW or 24 dBm), the current drawn by the module at the VCC pins is in the
order of continuous 600-700 mA. Even at lowest output RF power (approximately 0.01 µW or -50 dBm), the
current still remains in the order of 200 mA due to module baseband processing and transceiver activity.
An example of current consumption profile of the data module in UMTS continuous transmission mode is shown
in Figure 12.