Integration Manual

LISA-U series - System Integration Manual
3G.G2-HW-10002-A3 Preliminary System description
Page 29 of 160
antenna). This happens for 2.307 ms (width of the 4 transmit slots/bursts) with a periodicity of 4.615 ms (width
of 1 frame = 8 slots/bursts), so with a 1/2 duty cycle, according to GSM TDMA. If the module is in GPRS
connected mode in the DCS 1800 or in the PCS 1900 band, the current consumption figures are lower than in
the GSM 850 or in the E-GSM 900 band, due to 3GPP transmitter output power specifications (refer to LISA-U1
series Data Sheet [1] and LISA-U2 series Data Sheet [2]).
Figure 12 reports the current consumption profiles in GPRS class 12 connected mode, in the GSM 850 or in the
E-GSM 900 band, with 4 slots used to transmit and 1 slot used to receive.
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
60-130mA
Peak current
depends on
TX power
GSM frame
4.615 ms
(1 frame = 8 slots)
1.5
1.0
0.5
0.0
2.5
2.0
1600 mA
60-130mA
10-40mA
Figure 12: 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 12, representing the current consumption profile in GPRS class 12 connected mode,
is valid for the EDGE class 12 connected mode as well.
LISA-U2 series modules support GPRS and EDGE class 33: up to 4 slots can be used to transmit, as in the class 12
mode, and up to 2 slots can be used to receive in the same frame since up to 6 slots can be used in total. So, the
VCC current consumption figures in GPRS and EDGE class 33 connected modes are similar to the current profile
in GPRS and EDGE class 12 connected modes, since the same number of transmit slots are used.
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 500-800 mA (refer to LISA-U1 series Data Sheet [1] and LISA-U2 series Data Sheet [2] for
detailed values). 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/HSxPA continuous transmission mode is
shown in Figure 13.